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1957 BSA Spitfire Scrambler

Posted By: Magnetoman

1957 BSA Spitfire Scrambler - 07/07/13 6:49 pm

Restoring the World's First BSA Spitfire Scrambler ("Rocket Gold Star")

Introduction

This thread describes the restoration of my 1957 Spitfire Scrambler. It's going to be in two parts, possibly with an extended intermission between them. The first part will take events in chronological order as best I can reconstruct them, from my acquisition of little more than a butchered frame and an engine in 1994, through the process of identifying what I had purchased and how it had been originally configured, up to it being a nearly complete machine that is ready for restoration. I will include all of the material I have been able to find to date on this poorly-documented model, as well as describe an approach to restoring a motorcycle that not everyone will want to copy. The second part, once it starts, will continue through to the final restoration.

A Lucky Purchase

In the Fall of 1994 I was given the opportunity to buy an incomplete A10 based on only a few photographs. The machine looked to be in wretched condition (which later proved to be all too accurate), but the asking price was very low so I decided to buy it for the parts. When the box arrived at a friend's motorcycle shop there wasn't much in it, and what was there clearly had led a very hard life:

[Linked Image]

Inside the box were an engine in a frame, front and rear wheels and hubs, fork tubes (but no top yoke), an unidentified seat, a Std gearbox and an A65 frame:

[Linked Image]

[Linked Image]

Loosely assembling my purchase, what I had sort of resembled a motorcycle only if viewed from at least 20 feet away:

[Linked Image]

Although it would be silly to try to restore a fairly common BSA A10 starting from something this incomplete, even more critical than the many missing parts was that the headstock had been crudely hacksawed from the frame and even more crudely reattached in a very clumsy attempt to make a chopper. The "workmanship" was unbelievable, with short sections of galvanized iron water pipe stuffed in the downtubes to help rake the head, and with the entire assembly held in place with aluminum pop rivets and globs of poor welding. Evidence of all this was hidden beneath deep layers of epoxy body filler, some of which I removed before taking the following photographs:

[Linked Image]

[Linked Image]

However, the machine never could have operated in this form since the first modest jolt would have snapped the flimsy pop rivets and separated the front end from the rest of the machine. In spite of this, as I was to find once I had the production records, miraculously this particular engine and frame had managed to remain together since leaving the factory forty years earlier.

Delivered to me was only an engine, dangerously butchered frame, wheels, hubs and forks (minus top yoke), and Std gearbox. Still, I was happy enough, because I had paid very little for it.

[Linked Image]

Almost immediately after opening the crate I saw that the engine number ended with 101 which meant it was the first in some series. It turns out I have an unusually large library of English-language motorcycle books and manufacturers' literature, including indexed sets of a dozen magazine titles, so I assumed that as soon as I got home from my friend's shop it would be easy to find what year and model BSA this CA10SR101 engine came from… (to be continued).
Posted By: Peter R

Re: 1957 BSA Spitfire Scrambler - 07/07/13 7:39 pm

MM, I will look forward to watching your progress with this restoration .
The amount of mutilation to the frame really is unbelievable, I have seen several bodges on motorbikes, but what I see here certainly beats all.
The first bike of a series is rather unique indeed. Anyway, the restoration of this bike will surely keep you out of the pub for the coming months. Good luck :bigt
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/07/13 10:44 pm

Originally Posted by Peter R
the restoration of this bike will surely keep you out of the pub for the coming months.
Months? You mean decades...
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 07/08/13 4:40 pm

What we have here is certainly a top contender for the best-ever "before" photo!
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 07/08/13 5:36 pm

And so, it begins. As I recall reading in an earlier post, your pictures were on slides that you were planning to scan. They came up very nicely indeed. I'm looking forward to your thread.

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/08/13 6:53 pm

Originally Posted by TR6Ray
As I recall reading in an earlier post, your pictures were on slides that you were planning to scan.
I started this restoration long enough ago that the media those images were made on no longer exist -- the slides are Kodachromes and the less-saturated third photo is a Polaroid. Kodachrome and Polaroid no longer exist (Kodak itself barely exists), and slides are so obsolete that slide scanners are nearly obsolete. Just about everyone who was worried about transferring slides to digital with the highest possible quality bought slide scanners a decade or so ago and since then the market for such scanners, and thus the introduction of improved ones, has pretty much gone away.

Originally Posted by GrandPaul
What we have here is certainly a top contender for the best-ever "before" photo!
The reasons why will become clear (although the title gives it away), but I felt compelled to proceed despite this condition.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/11/13 11:58 am

What is this Bike That I Bought?

After removing enough paint and bondo from the headstock to reveal the frame number I then looked in all the books in my collection to try to identify it and the engine, but without success. The following letter shows why that was the case, and nicely illustrates the state of knowledge of these machines in the mid-1990s:

[Linked Image]

Roy Bacon handled technical inquiries sent to 'Classic Bike' magazine at that time and the above letter, dated only a few months before I got this BSA, was sent to me sometime later by another owner of one of these machines. Records from several manufacturers were held by the Science Museum Library in London (subsequently transferred to the owners' clubs) so my next step was to write to the librarian asking for whatever information they might have. As can be seen, the first letter I received back from Mrs Taylor dated it from 1958.

[Linked Image]

However, additional clues that I continued to find made me believe the information in her letter was incorrect so a few months later I wrote back to her again.

Historical aside for younger readers: although the first fairly broad email networks had been created in the early '80s (e.g. Bitnet, that I had been using since 1982), the mid-'90s were still the Dark Ages of the internet. The first bug-ridden browser, Mosaic, had been released only a year earlier so there were very few pages of any kind on the nascent web. Believe it or not, most people way back then still got essentially all of their information from books and communicated with each other by writing back and forth on pieces of paper that were placed in mail boxes.

A few weeks after I wrote to her a second time about this motorcycle I received corrected information from Mrs. Taylor saying it was a 1957 model:

[Linked Image]

That summer I happened to be in London so I visited the library in person. That would have been at least my third or fourth visit there to study various production records so by that point Mrs. Taylor must have recognized me a serious person because she started giving me direct access to the records for my searches. What those records showed was that my inexpensive purchase was the very first Spitfire Scrambler manufactured. My motorcycle was the first one of an initial batch of 65 machines dispatched to BSA's West Coast distributor on February 13, 1957 (a Hap Alzina bulletin I will include later in this thread shows that deliveries of these to dealers in Southern California began March 29). The fact the very first one to roll off the factory floor was still with us (albeit in butchered form) a half-century later was truly remarkable. Later I obtained a full set of the production records that let me determine other interesting things about the production practices that I'll discuss later in this thread.

Unfortunately, I now had a problem, not unlike that of a dog chasing a bus. What does the dog do if it actually catches the bus? Although I was lucky enough to find I owned the very first BSA Spitfire Scrambler ever produced, it was in horrible and incomplete condition. What to do? Had it been the second Spitfire it would have been easy to just cannibalize the parts for other projects. But, it wasn't the second one…
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/15/13 1:35 pm

The Importance of Information

Most post-WWII British motorcycles are relatively common and well documented. Although it might be difficult to find certain parts for a, say, 1950 Vincent Black Shadow, and expensive to buy them when they are located, at least the parts book tells you exactly what to look for. My problem with this BSA was quite a bit more difficult. What I needed to do was to locate a large number of parts, some of which had been produced in very low quantities, without a parts book ever having existed that would tell me what to look for. Sort of like being given a haystack without even knowing I was supposed to search it for a needle. So, for this restoration my first task was to locate whatever information I could find on this poorly-documented model (actually, this is the first task of every restoration; it's just that in this case it was for a bike that in the 1990s "no one" even knew existed).

Having determined my BSA was from 1957 I went through my collection of motorcycle magazines to see what I could locate, and quickly found the following in the April issue of 'Motorcyclist':

[Linked Image]

And the following in the May issues of both 'Cycle' and 'American Motorcyclist'. The identical photo and text indicates both magazines copied the story directly from a BSA press release so we can regard this as "official" BSA information:

[Linked Image]

To digress for a moment, production of BSA's 1957 models began at the end of August 1956, immediately after the factory's annual holiday break. A two-page story in the February issue of 'Cycle', "BSA Announces 1957 Models," describes the complete range of motorcycles for the new year, including a discussion of specific differences between versions destined for the East and the West coasts. However, no mention of a Spitfire is made. BSA would have had to have material for that issue in the magazine's hands by December, nearly four months after production of the 1957 models had been underway. Neither the East or West Coast edition of the 1957 catalog, "Printed in England" and then shipped by boat to the U.S. in time to arrive by early spring, mentions the Spitfire, nor is it in the initial East Coast 1957 price list issued to dealers at the start of the selling season. I infer from the content and timing of these pieces of literature that the decision to produce the Spitfire came very late and outside the normal planning process. Major changes to BSA's management took place in 1956, so perhaps my Spitfire is the very first tangible result of pressure from the U.S. for the new management to do something about a range that had changed very little since 1949. The only new sporting model introduced in all that time had been the Road Rocket.

These magazine articles gave me the first useful information to go on as I started tracking down parts. Also, my Amal literature for 1957 gave the specifications for a "650 c.c. American Scr. Twin." so I knew to start looking for a 376/89 carburetor. Just the way this particular model is listed in the Amal literature as a description of its intended use, rather than as a model name, also indicates it was a last minute addition to BSA's lineup. A year or two later I found a 376/49 at the Beaulieu autojumble (used on 1955-66 Velocette MSSs). Although the numbers after the '/' are irrelevant for functioning, this first Spitfire really does deserve a proper 376/89, so if someone reading this has one they want to sell please send me a PM or email to [email protected]

My persistent hunt for information slowly began to pay off, eventually turning up the following BSA literature:

[Linked Image]

[Linked Image]

[Linked Image]

The following sheet from Hap Alzina was particularly valuable since it lists the parts for this bike that are not in the standard BSA spares catalogs:

[Linked Image]

The parts I highlighted in yellow are from Gold Star spares catalogs, showing that for 1957 the Spitfire was the same hybrid that BSA re-introduced five years later as the Rocket Gold Star Spitfire Scrambler. Note, though, that this bulletin was issued a year and a half after the initial batch of machines was delivered to the U.S. I will come back to this point again later.
Posted By: Two Alpha

Re: 1957 BSA Spitfire Scrambler - 07/17/13 3:46 pm

Looking forward to the rest of the story, I think we're all fortunate that box of parts ended up in your hands.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/18/13 1:17 pm

Originally Posted by Two Alpha
Looking forward to the rest of the story, I think we're all fortunate that box of parts ended up in your hands.
Thanks very much for your comment. There's much more to come with this story.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 07/18/13 2:43 pm

THIS is a great thread.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/18/13 8:31 pm

Originally Posted by GrandPaul
THIS is a great thread.
I'm glad you like it. The next installment should be ready to upload by tomorrow.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/19/13 9:05 am

Identifying and Finding the Missing Parts

OK, one more post to get through about my approach to this restoration before some cutting, welding and bolting begins. As I located literature about 1957 Spitfires I was able to use it to begin creating an extensive "want list" of parts I needed, which in turn allowed me to start the slow process of tracking them down. Buying a motorcycle piece-by-piece certainly is the most time consuming and expensive way of building one, but I had no choice.

Well, actually I did have somewhat of a choice. It turns out I have a 1963 Matchless G15/45 that is also waiting for me to find the time to restore it. It came to me many years ago missing all of the sheet metal and since only 212 of these were made the problem of spares is somewhat like that of the Spitfire. However, in the case of the Matchless nearly all the cycle parts are the same as for their other bikes of the time so I found a complete 1962 G12 with blown engine to serve as a "donor bike." This was a lot cheaper and more convenient than tracking down the missing items piece by piece as I've had to do with the Spitfire. However, the same approach for the Spitfire would have required finding both appropriate A10 and Gold Star donor bikes from which I could strip parts. But, even then, there are enough differences between a Spitfire and standard A10s and Gold Stars so this wouldn't have been as helpful as it can be for other machines that are missing a large number of pieces.

Once I had my want lists, my process was to mail or fax them to suppliers in the U.S. and England, order the parts that they had, cross them off the lists as I received them, and then contact the next set of suppliers with my updated lists. However, I never sent the same want list to two suppliers at the same time because I don't feel it right to do this. For example, I might have tried SRM or C&D for engine parts at the same time I tried Len Haggis or Draganfly for Gold Star cycle parts. Once they sent me what they had, and told me what they didn't have, I would update my lists and send the revised lists out to the next set of suppliers. And so on, and so on.

Also, some parts I found at the Beaulieu and Netley Marsh autojumbles that I visited a couple of times during the 1990s, and others came to me through various contacts I had. The latter included, among other things, the proper top fork yoke, skid plate, exhaust pipes, ASCT scrambles gearbox as a "temporary" (for nearly 20 years) placeholder until I found an SCT2, and a dual carburetor head (that I probably won't end up using on this machine, for reasons I will discuss later in this thread). Although for many people ignorance can be bliss, I've always felt it better to know as much as I can about whatever it is I'm interested in so I've kept a running total of how much I've spent on all of this.

As an historical aside, even prior to September 11, showing up at Heathrow with 20 lbs. of mysterious pieces of metal in my suitcase always got me a personal interview with airline security personnel.

Custom Restoration Manual

Since there isn't a parts or workshop manual for this machine, during this time I put together one of my own from all of the relevant literature I have on A10s and Gold Stars:

[Linked Image]

I make these manuals for every bike I rebuild or restore by gathering all the information I can find and organizing it in appropriate tabbed sections in a large binder (or several binders). I couldn't find the file on my computer with the section headings of my Spitfire's manual, but the ones for my Gold Star are nearly identical:

___INDEX TO BSA GOLD STAR MANUAL___
PARTS MANUAL
Parts Manual
Part Numbers

ENGINE
Engine Disassembly
Engine Assembly
Rocker Cover, Rockers, and Valve Clearance
Head and Valves
Timing Chest; Timing, Magneto Removal, and Breather
Cams
Oil Pump; Lubrication System
Barrel and Piston
Crankcase and Main Bearings
Crankshaft, Flywheels, and Connecting Rod
Primary Drive
Clutch
Gearbox
Carburettor (G.P. 1&2, Monobloc, and Standard)
Exhaust System

CYCLE PARTS
Frame and Seat
Forks and Steering Head
Shocks and Swing Arm
Wheels and Brakes
Speedometer, Tachometer, Tools, and Special Tools
Controls, Levers, Cables, and Miscellaneous
Fuel Tank, Mudguards, and Other Sheet Metal
Paint, Transfers, Finish, and Fasteners

ELECTRICAL EQUIPMENT
Magneto
Lighting System (General)
Magdyno
Voltage Regulator
Battery
Head Lamp, Lighting Switch, and Ammeter
Horn, Tail Lamp, and Stoplight Switch

GENERAL
General Data and Specifications
Misc. Information
Initial Startup after Rebuild

The information comes from spares lists, workshop manuals, dealer bulletins, club newsletters, books and magazines, i.e. from everywhere I can find it. Whenever I come across something relevant for one of my machines I make a photocopy and add it to the appropriate manual. Although this always results in a given section having information that is redundant or contradictory I don't spend any time trying to resolve these issues when I'm assembling one of these custom shop manuals. When the time comes to work on the, say, the timing chest, I go through all the material in that section and decide at that point what information to use and what to ignore. I've found that even when a particular piece of advice is wrong there are times when it still can provide a useful insight into a way of improving the right way of doing some task.

Even though all the information in a major category like "Electrical Equipment" might be the same for two different machines I duplicate the content for each manual so it's all in one place for each machine. That way when I'm working on a bike I have everything that is known about that particular machine in front of me. Since each of these manuals is almost certainly the most complete shop manual in existence none of them fits in less than a bulging 2" binder (i.e. ~500 pages), and the largest requires four 2" binders (~2000 pages). If I can't find what I'm looking for in a manual I know there is no point to stop work and search elsewhere in the hopes of finding it.

Such manuals are particularly useful for the way I have to work, which is to rebuild or restore a bike in stops and starts, often with extended periods between sessions, and often while working on a completely different bike or bikes in parallel. I'm able to abandon jobs before they are finished and return to them days (weeks, months, years…) later with the minimum amount of wasted or duplicated effort.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/21/13 4:52 pm

Repairing the Frame

Beyond identifying (and then locating) all of the missing parts there was the troublesome issue of the butchered frame. The frame had to be dealt with before I started to order parts since if it proved impossible to restore that would have been a sufficient reason to abandon the project before getting in any deeper.

The first step was to sandblast the frame without degrading the numbers stamped in the headstock. Then the headstock was removed from the frame and the latter bolted to a rigid platform for subsequent work.

The following diagram from a BSA manual shows the required frame geometry:

[Linked Image]

Although I had brazed and gas welded for years up to that point, and had full access to a 20 kW TIG welder, I had never taken the time to learn how to use the TIG. So, I turned the frame over to a friend to rebuild for me. He had owned a motorcycle shop in the past, built various Honda dirt track racers over the years, and then ran his own motorcycle machine shop for two decades before retiring a couple of years ago. However, he moved everything to a shop at his house after retiring so f you need work like this done send me a PM and I will put you in touch with him.

Before starting to reconstruct the front he pulled all the sections into their proper positions according to the above diagram and tack welded braces to maintain that alignment during subsequent welding:

[Linked Image]

Using the BSA diagram, plus donor segments he cut from the A65 frame that came with the bike, my friend re-attached the headstock at the correct 27-deg. forward rake (and 0-deg. side-to-side with respect to the swinging arm pivot):

[Linked Image]

Although I used a large analog protractor with a magnetic base for the above photograph, my friend used my digital level with 0.1-deg. resolution for the actual work (as can be seen placed across the frame in the previous photograph).

[Linked Image]

[Linked Image]

After extracting tubes of the necessary lengths from the A65 frame my friend machined short stubs from other tubing whose OD was the same as the ID of the frame tubes to provide strength (i.e. these are not butt joints), TIG welded everything into place, and then smoothed the welds:

[Linked Image]

He then fabricated the appropriate half-height headstock brace as was used on these 1957 frames:

[Linked Image]

[Linked Image]

Having reattached the headstock and restored the frame to the correct geometry my friend then removed the braces he had tack welded into place to maintain alignment throughout all of the above and smoothed those welds. All of this work was by no means cheap, but I had dropped by his shop daily to watch progress so I knew how much time (and skill) he had put into it. Not that it matters, but he fit this work in during slack time between "real" paying customers. Still, given how much time was involved there was no question he seriously undercharged me, but he insisted he couldn't make me pay the full cost.

At this point I had a good-as-new frame and could proceed with the restoration. The bike was still in his shop but some of the work was transferred back to me. We removed the swingarm, replaced the bushings, and painted the frame. However, this was just a quickie paint job, basically to keep the frame from rusting, so I will be giving it a proper coat of paint when the time comes.

My approach to such a restoration is to do a trial assembly of everything to make sure all bolt holes line up, sheet metal doesn't touch where it shouldn't, etc. There are always problems to be resolved at this stage. Only after all parts have been made to fit correctly (which, of course, first requires having found all those parts) do I take it all apart to actually rebuild, polish, paint, send out for plating, etc. Doing it this way minimizes the number of disturbing discoveries of brackets or holes that have to be moved by ~1/8" in parts that already have been beautifully painted.

For reference, the following photograph taken directly from the front shows the location and layout of the frame numbers on these machines.

[Linked Image]

The bike was sold to me with a bill of sale only but I now had enough information to get a proper title for it. Someone from the motor vehicle department actually would do on-site inspections by appointment, and since it was still at my friend's shop it couldn't have been easier. I left a pile of documentation and references to this model that I had found up to that point for him to consult if he felt like it (which he did). He dropped by to inspect it during the shop's normal working hours and shortly thereafter the title for my 1957 BSA A10 Spitfire Scrambler arrived in the mail. At that point I packed up everything and moved the machine to my own garage to continue work.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 07/22/13 1:33 am

How sweet it is to have amazingly talented friends! It is so much better to be able to step in and observe/help as the work is in process. That way there are no surprises and you got to be involved throughout. Also, congratulations on progressing from a bill of sale to a title in your name.
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 07/22/13 6:04 am


Few things in life are sexier than freshly fettled and finished steel. Your friend does lovely work and is obviously a talented man.

Well done
Rod
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/22/13 7:19 am

Originally Posted by TR6Ray
How sweet it is to have amazingly talented friends! I
Originally Posted by Redmoggy
Your friend does lovely work and is obviously a talented man.
Indeed. His skills came to my rescue more than a few times over the years.

Originally Posted by TR6Ray
It is so much better to be able to step in and observe/help as the work is in process.
I always very much appreciate the opportunity to learn new skills, or improve old ones, from someone who knows more than I do. There's no way I would have known how to repair that frame 15 years ago but, thanks to him, I wouldn't hesitate to do it myself today. My goal is to be able to do all aspects of a restoration myself (rebuild engines, repair magnetos, weld frames, etc.), but there are still limits I haven't overcome (e.g. chrome and Cd plating -- real Cd plating, not simulated with Zn).
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/23/13 4:22 pm

Bolting It Together

Luckily, as literature earlier in this thread shows, most of the non-A10 cycle parts on this machine are standard Gold Star items so, after having had the frame reconstructed, over the next two years I was able to locate the majority of the missing items. With one significant exception. Unfortunately, though, the one missing piece was major: an SCT2 gearbox. What made this such a serious problem is the gearbox was only used on 1957 Spitfires making it much rarer than its fraternal twin, the treasured RRT2 used on the Clubman Gold Star.

The following two photographs from 1996 or '97 show that by then I had the major components loosely bolted together in the reconstructed frame, with it now looking remarkably like an actual motorcycle. The Std gearbox that came with it is still in place in these photos, but in late 1997 I bought an ASCT from a 1962 Gold Star Catalina to use as a "temporary" scrambler gearbox until an SCT2 turned up. I also had the oil tank, mudguards (and stays) and seat so I essentially had all the makings of a complete machine by this time.

[Linked Image]

[Linked Image]

Comparing these photos with the ones at the start of this thread shows that I had made considerable progress on this restoration, although clearly much remained to be done. However, it sat in basically that same condition for the next fifteen years as other things kept coming up to occupy my time. Still, I kept chipping away at the remaining items on my want list, locating such hard-to-find items as the 1" carburetor spacer from the 1958 Alzina parts list (which I probably won't use after all, for reasons I will give in a later post) and the plates for covering the holes for the dynamo in the motor mounts. I also picked up a rare dual carburetor head, a set of crossover high pipes from a later model Spitfire, and an alloy scrambler tank (none of which I now plan to use on this bike, again for reasons to be given later).

As an aside, the dual carburetor A10 heads that were offered as a speed kit accessory at the time are now often missing the small inlet manifolds. You can find information about these heads and manifolds on the web, for example at:

http://www.beezanet.com/twincarb/whydidbsa.htm

Interestingly, a pair of these manifolds appeared on eBay last month, attracted 8 bidders, and sold for a rather remarkable $355. Given how hard it is to find these manifolds, without which the heads are useless, it's worth pointing out that the moderator of the Norton Forum, Dave Comeau, offers reproduction manifolds for less than a third of this.

Although plenty of other motorcycle-related things took my spare time over the past fifteen years, other factors also could have been involved in the lack of additional progress on the Spitfire (sloth, laziness, ...). But, the missing SCT2 gearbox certainly affected my motivation to start actual restoration work. This was a significant deterrent because even had I fully restored the machine using the ASCT it would have taken quite a bit of work to swap gearboxes later. Plus, no matter what, an SCT2 gearbox is one of the key defining elements of this machine so it just wouldn't be a "properly restored" 1957 Spitfire Scrambler without it. Unfortunately, despite finding nearly all of the remaining bits needed for the restoration, in all that time I did not see a single SCT2 for sale.

Finally, an SCT2

Finally, a little over two years ago I got a notice from eBay that an SCT2 had just been listed. Obviously, I had to have it. Although 15 other people bid on that gearbox over the next week, none of them was nearly as desperate as I was to own it, and when the auction ended it was mine. What those other people didn't know was they were just wasting their time bidding because there was no way I wasn't going to have it. However, as these things seem to happen, after not seeing a single SCT2 for many years, two months later another one appeared on eBay. Although that one was in quite poor condition, 17 bidders ran the price up to 15% more than I paid for mine. I suspect a few people who had lost out on "mine" realized they were very lucky to be given this second chance and tried hard not to let it happen to them again. Out of curiosity I left my eBay search in place, but no further SCT2s have surfaced.

[Linked Image]

As a point of information, the number 423084 is stamped in 1/8" numbers on the back face of their middle casting of this gearbox, above the raised casting number '67-3345'. I have seen it stated that scrambles boxes should be stamped with 423083, but both my SCT2 and ASCT are stamped 423084.

[Linked Image]

Appeal for Parts Needed to Restore the World's First Spitfire Scrambler

Although there is much more material to come in this thread, I'll pause for a moment to make an appeal. The only significant pieces still missing today that are needed to return this machine to its original condition when it was the first one to roll off the assembly line are:

2-gallon Gold Star tank
Exhaust pipes (42-2797 right; 42-2799 left)
Competition Number Plate (65-6616)
Amal 376/89 carburetor

Clearly I could fabricate the pipes and number plate, and having the /89 suffix on the carburetor isn't critical for functioning. But, given its "historical significance," this particular machine deserves to have the highest percentage of original components on it as possible. So, if you have any of these taking up room in your garage and would be interested in selling them to aid this "historic" restoration please send me a PM.

If you would rather trade (or just want to buy it outright), the fairly rare ASCT I bought as a placeholder 15 years ago is now surplus to needs and will just continue to collect dust on the shelf as long as I have it. This was used only on 1962 Catalina Gold Stars but it has the same ratios as the ARRT of the 1962 Gold Star Clubman and 1963 Rocket Gold Star, as well as the ASC of the 1963 Rocket Gold Star Spitfire Scrambler (why BSA used so many codes for the same ratios is speculation for another day). If you think you ever might want to build a RGS replica, this has the right ratios for you…
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/28/13 11:03 pm

Rolling Work Stand and Customized Hoist

After the SCT2 showed up I fabricated a rolling work stand for this machine that lets me pull it into a central position in my garage when working on it, and then shove back into "storage" when I need the space for working on something else. As the following photograph shows, two other bikes also are parked on these rolling stands waiting to be restored. One is the 1963 Matchless G15/45 mentioned in an earlier post and the other is a… well, I'll try to get to that in a future thread.

[Linked Image]

I have an hydraulic lift that is very handy for maintaining my bikes that are already running, but I don't want to tie it up for years on a restoration like this one. And, even if there were ample space for more of these lifts it wouldn't make much sense to have its capabilities but just leave it locked in the elevated position for years at a time. Anyway, wood rolling benches are perfect for my purposes as well as being cheap to make. It's easy enough to do "one-time" lifting of a bike onto one of these benches with my customized engine hoist (discussed below), and then to lift the restored bike off again the same way months or years later when it's done.

I make these stands from 4x4s (legs), 2x6s (cross pieces at ends and in the center), and 2x2s (support for lower shelf) with surfaces of 1/2" plywood, all of which are cut for free by Home Depot to the dimensions I specify. Then it's just a matter of drilling pilot holes, bolting them together with 1/4" lag screws, and adding eyebolts at the corners for tie down points and casters for moving them around. The casters I use are rated for 150 lbs. ea. so are ample for this, and I paint the tops with white gloss enamel to make it easier to see small parts as well as to make it easy to mop up oil spills.

I make these stands 25" high and 2x6 ft. For what it's worth, these aren't "random" dimensions, but are ones that I actually gave some thought to before deciding on them. The top of my hydraulic hoist is 3" wider and 15" longer, but that additional surface area isn't needed for any of my machines and only results in it taking up additional space in my garage (my stands are shorter so the front and rear edges of the wheels overhang, but that's irrelevant for function). Also, in its highest locked position the hydraulic hoist sits 1-1/2" higher than my wooden ones. While taller is better for working on the engine, it's worse for working on the top of the forks, so no matter what height is used it will be a compromise. Obviously, someone 6 ft. 4" would want one a different height than someone 5" 4" (I'm 5" 10"), but these dimensions have worked out very well for me. The next photo shows a motorcycle being installed on one of these stands (this stand is slightly different than the one for the Spitfire since I built this one using a heavy duty cart I already had).

[Linked Image]

This photograph also shows my customized Harbor Freight 1 Ton engine hoist. I increased its height by 15" using 1/8" wall steel pipe (not water pipe; along with two 15" sections of 2" square steel tubing) and its lifting capacity to a full 1 T with the boom fully extended (1.6 T with the boom at the shortest position). The increased lifting power is due to replacing its hydraulic cylinder with one that is 6000 lb. (3T) which gives 1 T at the hook thanks to the 1:3 leverage. Since the boom assembly has been raised by 15 in. the 2" x 1/4" Al pieces at the back raise the stabilizing straps by the same amount. Although the boom is almost certainly strong enough as-is, 2" square steel tubing is an excellent fit inside so I inserted a full length piece to roughly double the strength. Two pieces of 1" square steel tubing at about 45-deg. keep the raised "foot" of the lift from trying to move backward, and two lengths of braided aircraft cable keep it from trying to move forward. I estimate such forward/backward forces are less than a few hundred pounds even when lifting the maximum weight so these braces are much more than sufficient to deal with these forces. I constructed it this way, rather than by welding, to allow experimenting with different heights. But, I've been quite happy with its 15" additional height and don't feel any need to replace the "temporary" braces with welded ones so the current configuration shown in the above photograph likely will be the permanent one. I used this modified hoist with the boom fully extended to lift an ~1800-lb. milling machine on and off a trailer without it showing any sign of distress so I don't have any concern using it with 400-lb. motorcycles.

As can be seen from this photo the height and configuration of this modified hoist makes it easy to lift bikes on and off these stands (motorcycle obscured for dramatic purposes, since it will be the subject of another thread I may be starting before too long). The reason I chose to customize a 1 T hoist rather than just using a standard 2 T version is because my modifications give me one that is both taller and takes up quite a bit less floor space when in its folded configuration than the 2 T, while providing the same lifting capacity.

Additional lifting help is always nice to have, especially for jobs like maneuvering an engine into the frame single-handed without scratching any paint. Although the engine hoist would work for this, I made a "jib crane" from Unistrut along with a Unistrut trolley rated at ~425 lbs. This crane bolts to the side of these stands and, along with a ratchet-operated 40"-travel chain hoist, lets me lift and position heavy items. It is very handy for such tasks even where it isn't "essential," like holding a wheel in position at the correct height in order to measure the length needed for a spacer. Unfortunately, I don't have a picture of it attached to a stand. It's attached to the mill as I write this where it does triple duty with it and my lathe as well.

The lower shelf on each of these stands lets me keep most parts for a given restoration with the bike itself so (almost) everything is all in one place. In the case of this Spitfire the exceptions are a "donor" A10 engine I bought in 1997 in case I might want to cannibalize parts from it, seat, a beautiful alloy scrambler tank (which I now don't plan to use on this restoration), crossover high pipes from a later model Spitfire (again, I don't plan to use them), mudguards and oil tank.
Posted By: JBMorris

Re: 1957 BSA Spitfire Scrambler - 07/29/13 12:43 am

Nice job!

Quote
After extracting tubes of the necessary lengths from the A65 frame my friend machined short stubs from other tubing whose OD was the same as the ID of the frame tubes to provide strength (i.e. these are not butt joints), TIG welded everything into place, and then smoothed the welds:

Just curious why this method is not considered a 'Butt-Weld' when there is no evidence of a 'half-lap' scarf or even drilled holes for 'plug' welding?

Pardon the insolence here,just a self-taught student of welding science that only graduated to the oxy-acetylene variety. . .
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/29/13 2:25 am

Originally Posted by JBMorris
Just curious why this method is not considered a 'Butt-Weld' when there is no evidence of a 'half-lap' scarf or even drilled holes for 'plug' welding?
I was only able to photograph the frame when I dropped by after work so, at a minimum, there is a full work day (or two, or maybe even three) between the "before" photograph showing a piece that had been cut from the A65 frame being fit to size, and the next "after" photograph showing the frame after all the prep work for the welding had been done, as had the welding itself, and the grinding down of the welds so only the appearance of smooth tubes remained. My friend would have to be a very poor welder indeed if any evidence of his welding were visible in the "after" photograph.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/29/13 2:03 pm

To add something on the subject of alignment and welding of the frame, there were four tubes that had to be reconnected, and the lengths and positioning of all four of them is fairly critical. Consider just the two down tubes. These are ~3" apart at the bottom of the place where the new sections have to be added. If one of the replacement sections were only 1/16" longer than the other the headstock would be twisted sideways by ~1.2-degrees. Since it's ~36" from the headstock to the road, this means the tire would be offset 3/4" to the side of the proper track. Further, even if these two tubes were of identical length, but they were either too long or too short (with respect to the other two tubes), the rake of the headstock would be wrong and/or the headstock would be too high or too low. Because all four tubes come into the headstock at a variety of angles the geometry is quite complex.

Because of the above, what was required of my friend was a fair bit of "cut and try" fitting to get the lengths to what they needed to be in order for the final frame geometry to be correct. Then he had to tack weld each section into place, re-measure to determine what movement/distortion had resulted from each tack weld, adjust for that, and tack the next section into place. And so on. If you look back at the first few photographs in the post showing the welding you will see a jig my friend made to hold everything in proper position. Although that jig isn't in the later photographs, he still was moving it in and out of position as he pieced the frame back together.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 07/29/13 2:08 pm

Looks like you are lifting a contestant for "world's largest chocolate" there...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/29/13 2:16 pm

Originally Posted by GrandPaul
Looks like you are lifting a contestant for "world's largest chocolate" there...
It's not chocolate, but many people would find it every bit as tasty...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/05/13 12:08 am

Overall Specifications of 1957 BSA Spitfires

Before returning to my particular restoration, a few posts with relevant information about this model in general.

How is this BSA different from all other BSAs? The answer is, the 1957 Spitfire Scrambler was a hybrid consisting of a modified Road Rocket engine (including type 357 "full-race" camshaft and 8:1 pistons) housed in a Gold Star Catalina-style scrambler frame without passenger footpeg loops, and with Gold Star cycle parts, including the front and rear mudguards, hubs, and forks. Supplied without lights, speedometer, or mufflers, it was intended strictly for off-road competition. Reflecting the reduced cost of producing it in this form, the Spitfire was priced $102.38 less than the Super Rocket.

Similar to what was done with the Catalina and the later Rocket Gold Star, the frames were given their own numbering sequence ('CA7Axxx'). Spitfires soon began winning races in the U.S., taking three out of the top four positions in the September 1957 Peoria National Championship T.T. The machine was even popular enough for several companies to advertise aftermarket accessories specifically for it. However, after producing just over four hundred of these disguised "Rocket Gold Star Spitfire Scramblers" in 1957, the next year BSA switched to using standard A10 cycle parts, thus putting the idea for a hybrid on hold until its time came again six years later.

As for how the Spitfire was configured, a 27 March 1957 press release from BSA's West Coast distributer Hap Alzina says, "Original projection on the Spitfire Scrambler was that a special scrambles camshaft would be most applicable for the basic purpose of the machine. However, careful dynamometer and road testing disclosed extraordinarily satisfactory performance with the full-race camshaft and hence this fitment has been adopted as a standard component, an engineering accomplishment that will be welcome news to 'drag-race' enthusiasts as it confines the necessary alterations from drags to scrambles to the top-end of the engine." It goes on to say that the owner need fit only a few components, rather than some previously-announced "Drag-Kit," and gives those components as "S&W Special High-Rev Valve Springs," along with sets of "special" valve collars and keepers. An October 1958 bulletin issued by Alzina itemizes 31 special parts for the 1957 Spitfire Scrambler that are not listed in standard parts catalogs. The principle defining ones are 67-1127 for the head, 67-357 for the camshaft, and SCT2 for the gearbox (separately listed from the 31 other parts, although on the same bulletin).

Production Numbers

How many of these unusual racing machines were made? The first batch of West Coast machines are listed in the "equipment" column of BSA's dispatch records as A10RS, while the initial East Coast machines shipped a month later are listed as A10R/S. Despite this, my engine is stamped CA10SR. However, hand written and circled on the page of the dispatch records with the listing of my machine, above the engine number column, is CA10SR as is stamped on my engine, although this notation isn't on any of the other pages. There also are A10R/RS, A10RRS, A10R/R and plain A10 machines listed as having been shipped to North America between February and September of 1957. Before concluding that some of these are not Spitfires, all are sequentially numbered with the frame prefix CA7A. The unique final 'A' continued to be used in subsequent years on Spitfires -- EA7A in 1958, FA7A in 1959, and finally GA7A from 1960 through the end of production in 1963; as far as I can determine there was no DA7A -- but not on other A10 models, apparently indicating use of the Gold Star Catalina-style frame without passenger footpeg loops.

The records show that only after the last of the U.S.-bound Spitfires had left the factory on September 17 did any find their way elsewhere. My count of the BSA's in the frame series CA7A shows that 364 machines (~87%) went to the West Coast, 53 (~13%) to the East Coast, 5 (1%) to Canada, and 1 each to the U.K. and to Japan. That makes a total of just 424 1957 Spitfires (although the engine number of the one sent to Tokyo was "recycled" from a machine shipped to the U.S. three years earlier, so there really were only 423.5). This relatively small number of a special purpose machine should be seen in the context of AMA homologation rules at the time which called for a minimum of 25 to be produced to qualify for Class C racing. I have to wonder if this model represented a short-lived effort to enhance BSAs presence in American racing that management reconsidered after one year, reverting to "standard" A10s for this model. In any case, relatively few of these Spitfires were made over a half-century ago, and only a fraction of those would have survived the rigors of off-road racing, making any of the ones still around today rare indeed.

It is clear from the dispatch records that Spitfires were assembled in order of engine number. My motorcycle with engine number 101 left the factory on February 13 but frame number 101 wasn't dispatched didn't until March 20. That one was sent to BSA's Nutley, New Jersey distributorship. Although there is a very high correlation between engine number and dispatch date, and poor correlation between frame number and dispatch date, the factory's practices sometimes resulted in minor variations in the sequence. This is to be expected since six separate assembly lines were operating in the factory at this time (twins, Gold Stars, M20s, etc.). After each machine came off the assembly line it was turned over to one of about a dozen riders for a road test, after which it pulled aside long enough for any problems to be rectified. After any necessary repairs had been made it was moved to one of the packing bays for the major components to be removed and wrapped (handlebars, front wheel and forks, silencer, seat, etc.), and the machine crated for shipping. Only then was it taken to the dispatch department. Because the factory's entire production was taking place in parallel, each step in this process provided an opportunity for any given Spitfire to slip by another in shipping sequence. However, the Spitfire with lowest engine number 101 also has the lowest "Tally No." and "Consignment Note No." in the dispatch records, leaving no doubt it was the first one manufactured.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/09/13 10:13 pm

Appeal for Several Parts for this "Historic" Restoration

As mentioned earlier in this thread, with only a few exceptions I have managed to collect everything needed to restore this machine to the configuration it had when it was the very first one to roll off the assembly line in February 1957. As an update to what I wrote before, after having looked for one for 15 years, very recently I was lucky enough to find a 376/89 carburetor. This was the last of the components containing stamped ID/type numbers (engine, frame, gearbox, and carburetor) identifying it as having been on a 1957 Spitfire. Even though the "temporary" 376/49 that had been on the machine for over a decade is in every way -- other than the lack of /89 -- identical, finally with the arrival of this carburetor the puzzle feels complete. Rusty, disassembled and in poor condition, but essentially complete. However, still missing are a few "generic" BSA items:

2-gallon Gold Star tank
Exhaust pipes (42-2797 right; 42-2799 left)
Competition Number Plate 65-6616

Clearly I could fabricate the pipes and number plate but, given this machiine's "historical significance," I would like to have the highest percentage of original components on it as possible. If you have any of these for sale or for trade (I have a fairly rare ASCT gearbox I no longer need), please send me a PM or an email to [email protected]

Additional Literature -- Part I

Following is the first of two posts that will contain a collection of bulletins, ads and other literature in chronological order that is relevant for 1957 Spitfires and that I had not already included in previous posts. Unless I've overlooked something in my collection, when finished this thread should include everything that I have been able to find on this machine. Therefore, if you are aware of anything additional, please take the time to scan and upload it.

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Hap Alzina Press Release. March 27, 1957.

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BSA price list dated May 4, 1957. I don't know if this list is for the East or West coast, but I also have an undated 1957 East coast price list that does not include the Spitfire. Presumably that other list was printed before the decision was made to produce the Spitfire.

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Cycle Magazine. May 1957.

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Motorcyclist Magazine. July 1957.

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Southern California Motorcycle News. August 1957.

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Cycle Action Magazine. August 1957.

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BSA (East) bulletin. Summer 1957. This is one side of a double-sided bulletin the other side of which was in an earlier post.

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Cycle Action Magazine. October 1957.
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 08/10/13 3:28 am


I'm desperate to see more pics, but really enjoying the bikes history.

Cheers
Rod
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 08/10/13 3:28 am


I'm desperate to see more pics, but really enjoying the bikes history.

Cheers
Rod
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/10/13 4:33 am

Originally Posted by Redmoggy
I'm desperate to see more pics, but really enjoying the bikes history.
How's this for a quick pics fix?:

[Linked Image]

It's the best I can do for the moment. It's the flange of the carburetor I finally lucked into after looking for 15 years. The Amal "Settings List" shows it was used on 1957-58 "American Scr. Twin" (the list doesn't show anything for 1959 Spitfires, jumping to 1960 for the next one). The Hap Alzina bulletin earlier in the thread shows this is the carburetor I need, and also gives the settings for it. Interestingly, these two lists differ significantly on the settings:

_____________Amal____Alzina
Main jet_______400_____240
Needle position__4_______3
Cutaway______3-1/2_____4

Yet another puzzle to deal with in this restoration.
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 08/10/13 9:00 am


With a resto like this, one of the things i find most impressive is the patience people have. I simply could not wait 15 years to find a carb, not when number stamps are so cheap!

Good on ya Mate
Rod
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 08/10/13 9:01 am


With a resto like this, one of the things i find most impressive is the patience people have. I simply could not wait 15 years to find a carb, not when number stamps are so cheap!

Good on ya Mate
Rod
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/10/13 3:33 pm

Originally Posted by Redmoggy
With a resto like this, one of the things i find most impressive is the patience people have. I simply could not wait 15 years to find a carb, not when number stamps are so cheap!
With a restoration like this one it helps a lot with the patience to have more than one motorcycle running as well as more than one motorcycle that I'm restoring (or pretending to myself they're being restored, not just collecting dust). But, in each case the only customer for my restorations is me, and I have to do the work in the way this customer insists on having it done.

Aside from any other issues, because this Spitfire was the very first one produced I wanted an actual /89 carburetor on the machine as it had when it was made, not just a carburetor stamped /89, and I would know the difference no matter how well any such restamping were done. If it had been the second Spitfire ever produced the /49 I found for it 15 years ago would have been just fine.

p.s. It's worthwhile mentioning that the /49 or /89 were just codes used by Amal to denote distinct differences in the assembly of carburetors so that they could supply an identical replacement whenever requested. As little a difference as having the needle on the 3rd notch for one unit and the 4th for another resulted in a completely different assembly code. Codes were issued in numerical order as the configuration was determined, so /1 was issued the year the Monobloc was put into production and, say, /101 came some years later (I could look up real dates and machines but won't take the time). However, because the same configuration could have been used on a given model motorcycle for several years, there isn't a strict one-to-one correspondence between /xx and the year of machine.

Anyway, while any Monobloc of the correct bore easily can be reconfigured with different jets, needle settings, etc. to be functionally identical to any other, the /xx number identifies the original machine it came on. Although a carburetor is a smaller component than a gearbox, I searched for a /89 for this particular Spitfire for the same reason I had searched for an SCT2.
Posted By: Dave McR

Re: 1957 BSA Spitfire Scrambler - 08/11/13 10:19 pm

What I love about this thread is the detail. I have found a kindred spirit in Magnetoman! I am new to this forum and also new to BSA. I have restored a couple of Kawasaki's but really wanted to turn my attention to an old Brit. Being an old Brit myself now in the USA. I searched for the right project and finally thought I had found it. Craiglist ad for a couple of "basket case" A65's. Turned out to be not 2 but 3 B44's. Matching frame and engine numbers from 1967. As much as it makes me want to dive in and start, to me, the research and collection of data from around that time is as much fun (and equally important) as the actual restoration. Great thread, love what you are doing here.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/12/13 6:05 pm

Originally Posted by Dave McR
What I love about this thread is the detail... the research and collection of data from around that time is as much fun (and equally important) as the actual restoration
I wrote in the first post in this thread that mine would be "...an approach to restoring a motorcycle that not everyone will want to copy" so I definitely appreciate your comment.

The nice thing about restoring any post-WWII British bike is that lots of similar machines were produced so even with rare ones like this Spitfire (or RGSDave's ongoing T100R restoration) 99% of the parts are common with the mass produced models. Unfortunately, finding that last 1% can be very frustrating. However, the key to finding all the missing parts is first to do the research to know exactly what those parts are, and then to relentlessly hunt for them until everything has been crossed off the want list. Even if/when it takes 15 years...

Note to RGSDave: if you're reading this, be sure to use one of the extended aftermarket bolts on whatever magneto you use until a BTH TTS6 turns up. With one of those bolts it's an easy job to swap magnetos, but with an OEM bolt a lot of parts have to come off the bike before you can remove the magneto.

Another note is that, unfortunately, there are basically two kinds of owners of BTH TTS6 magnetos (or any other rare part we need): those who have them in boxes somewhere in their garages but don't remember they have them; those who know they have them but won't sell them. This is why some parts require a decade of searching before they turn up.

I'll try to get the second installment of Spitfire-related literature uploaded later today.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/13/13 2:38 am

Additional Literature -- Part II

This completes the items of additional literature having to do with 1957 Spitfires that began in the previous post. Again, if you are aware of anything additional, please take the time to scan and post it to this thread. With the next post I'll start extracting information from this literature that I need in order to do an accurate restoration of my machine.

Addendum: BSA Parts Service Bulletin G.A.2 dated July 1957 attached at the bottom of this post says in the interests of standardization a new crankshaft has been fitted to standard, Super Rocket, Standard Rocket, and Scrambles Rocket A10s, with the part numbers for the old and new crankshaft and flywheel assemblies:

Old A10 Std: 67-774
Old A10 RR: 67-1149
New Part no. 67-1216

Catalogs MC991-2 (no date) and MC1009-2-2 (reprinted April 1958) both cover 1954-1957 A10s including Road Rockets. Both give 67-1216 as the part number of the Road Rocket assembly, but 67-663 for the standard A10 (for the standard A10 the part no. includes the rods).

Catalog 1009-3-3 covers Super Rockets from engine CA10R-6001, which was 1958. It gives 67-1216 as the part number for the A10 and A10 Super Rocket.

Since catalogs are updated to include the specifications at the time of printing, short-lived intermediate part numbers, like 67-1149, that were superseded can be missed. In any case, Bulletin G.A.2. says the new crankshaft was fitting to the "Scrambles Rocket" after engine number "C.A.10SR.231" which means the initial 130 Spitfires, including mine, came with the 67-1149 assembly.

Interestingly, crankshaft 67-1149 was superseded sometime during the 1957 model year[*] but the part number does not show up in the 1959, 1962, or 1963 Master Priced Lists (which include superseded parts). However, it does show up in 1965 (and 1970) with the comment to use 67-1216.

[*] Bulletin G.A.2. says "Scrambles Rocket" after engine CA10SR.231 were fitted with the new crankshaft, and that bike was despatched 5 May 1957.


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BSA (East) bulletin. Fall 1957.

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Cycle Magazine. November 1957.

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American Motorcycling. November 1957.

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Southern California Motorcycle News. February 1958. Because this advertisement was printed so early in 1958 and shows a machine with a racing number and custom pipes it is almost certainly a 1957 Spitfire.

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Southern California Motorcycle News. May 1958. Although there is no way to be certain, it seems likely that the photograph in this article was taken of the rider during the previous season, in which case it shows a 1957 Spitfire.

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Hap Alzina Bulletin. October 1958.

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Hap Alzina Bulletin. circa 1960.

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BSA (East) bulletin. July 1963.

Attached picture Crankshaft_new01.jpg
Attached picture Crankshaft_new02.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/15/13 10:05 pm

Specifications for Rebuilding the first Spitfire: the Unknown Unknowns

Overview

Donald Rumsfeld, perhaps the world's leading expert on pre-unit BSAs, responded to a question about restoring a 1957 BSA Spitfire Scrambler by pointing out:

There are known knowns; there are things we know that we know.
There are known unknowns; that is to say, there are things that we now know we don't know.
But there are also unknown unknowns – there are things we do not know we don’t know.

http://www.youtube.com/watch?v=26CvN46xBbo

My intention is that this thread contain the maximum of known knowns and the minimum of known unknowns about this machine. Ideally there wouldn't be any unknown unknowns, but the best I can do is to minimize the chances of having them.

Give its "historical significance" as the first "Rocket Gold Star Spitfire Scrambler" ever produced, I would like to restore the machine as accurately as possible to original condition. However, despite the literature I've collected over the past 20 years, there are difficulties in determining precisely what that means. For example, some photographs show the Spitfire with a passenger grab rail, while others show it without. Since panchromatic film is somewhat less sensitive at the red end of the spectrum, reds appear darker in B&W prints than does silver. Inferring the color of the tank from some photographs it is red (as is mentioned in some documents), while in other photographs it is silver (as is mentioned in other documents).

It is important to realize that BSA made changes to their specifications during a production run. When they did, spares manuals that were subsequently printed did not list the original parts that had been replaced with different ones. An example of this is the initial post-War ZB Gold Star heads had a large cavity for hairspring valve springs (although coil springs were used from the start). This soon was replaced with an altered head, but only the latter head was listed in the later ZB spares manual.

The reason the above is relevant is the October 1958 Hap Alzina bulletin shown earlier in this thread was issued 18 months after the first batch of Spitfires was delivered. That bulletin says "Parts listed below are not shown in the regular exploded view Spares Catalogs." where from the context it is clear they mean the A10 spares catalog. For the "Spitfire Scrambler 1957" there are 31 parts listed, including the frame, with most of the cycle parts from Gold Star lists (DBD as well as earlier). Because of BSA's practice of not documenting changes that were made during a production run, all we can assume is the Alzina list describes the ultimate specifications of this model, i.e. not necessarily the specifications of the ones made earlier in the production run, which may or may not have been the same as the last ones.

As mentioned earlier, the 1958 version of this machine basically was a modified A10 rather than a modified Gold Star. For the "Spitfire Scrambler 1958" there are only 8 parts listed, with six of those just mudguards and stays. The other two are a 19" rear rim and 42-6339 "Rear Wheel Assembly." I haven't tried to find that rear wheel assembly in catalogs, but it's the only significant part listed for 1958 that this Alzina bulletin says isn't straight from the standard A10 spares list.

In addition to the possibility of undocumented changes during the production run, making my quest for authenticity more interesting is that the February 1958 'Cycle' magazine has an article about the forthcoming 1958 BSA models, and about the Spitfire it says: "The Spitfire Scrambler will be continued exactly as introduced in the 1957 season... Finish is silver and chrome tank...". The text for that article, which clearly is just a reprint of material supplied to them by BSA, would have had to have been in the magazine's hands by ~December 1957 to make it into that issue. Since we know the 1958 version actually was produced as a stripped down A10 rather than as a Gold Star hybrid, what this means is that sometime after December the situation changed. Again, though, this article does say the 1957 tank was silver, contradicting at least some other BSA literature that says it is red.

The same October 1958 Alzina bulletin also has an exploded diagram with part numbers for the "Spitfire Scrambler Gearbox with Needle Mainshaft and Layshaft - 1957 Only". Again, the "1957 only" in this Alzina bulletin directly contradicts the press released-based article in 'Cycle' that says the model for 1958 "will be continued exactly as introduced for the 1957 season." While we already know the 1958 version was different, the point is that even when information is in writing it cannot simply be taken at face value. All available information has to be collected, evaluated, and then the best informed judgment applied to arrive at the most reasonable conclusion.

What Photograph Should be Used as a Guide for the Restoration?

BSA used the same studio photograph in all of their advertisements in 1957. For several reasons I believe this is a factory photo of a pre-production model and thus it only roughly represents the configuration of a 1957 Spitfire. For example, an inset in one of the ads has a "flying Spitfire" that is lacking the number plate, showing this machine has at least slightly different specifications than the production model.

The next photograph is a composite of two of these official BSA photographs, from an advertisement in 'Cycle' magazine and from a BSA Nutley press release. I brought them into Photoshop, overlayed them with BSA Nutley on top, made BSA Nutley 50% transparent, and aligned the bikes in the two layers. You can see from the slanted "National Champion T.T. Racer" text that the Nutley ad had to be rotated a few degrees (2.7-deg. to be exact), but that otherwise the two photos are identical.

[Linked Image]

This is further seen in the two enlarged insets to the right, of the rear tire and of the reflection in the right exhaust pipe. Every knob, spoke, and reflection is identical in the two photos. Given that the evidence indicates this machine is almost certainly a studio photograph of a pre-production model my conclusion is that it can't be used to determine what size or color of fuel tank was used. Or, for that matter, for any other detail (e.g. whether or not there should be a passenger grab bar).

Earlier in this thread are press release-based stories from three magazines (the identical text was used in two of them). The 27 March 1957 Hap Alzina press release says deliveries will commence two days later, implying the machines were already in the hands of the distributor when the release was issued. Although there isn't much time between then and the April cover date of the 'Motorcyclist' magazine issue that contains a story and a photograph, anecdotal evidence I collected is that issues of this magazine were sent out late during that period. The same photograph appeared in the May issues of Cycle and American Motorcycling. Hence, my conclusion is the photo in these magazine articles is almost certainly a photo of one of these first Spitfires. The use of a sheet as a backdrop further indicates a lack of time to take the machine to a studio for a proper photograph. Because of the timing of these events my conclusion is it is highly likely that the photograph in these three magazines was made in the U.S. of one of the first batch of Spitfires to arrive. That batch included my machine, so this is an excellent photograph to use as a guide in my restoration.

Clarification:The tank in the photo shown in this post is not the one I believe belongs on these machines. The one I believe is correct is shown in the two magazine articles that are in my third post in this thread (dated July 15).
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/23/13 8:49 pm

This and the following one or two posts will describe how I addressed several configuration issues that had to be dealt with before I could begin to properly restore this machine.

Fuel Tank Color

As mentioned in the previous post, the March Alzina press release says the tank is silver, while the undated east coast literature (that uses the same photo as in the magazine articles) says it is red. I am unaware of any other factory literature that refers to anything but these two colors. Whether this is a possible West/East coast difference, or a change in color for everyone in mid-year, or a mistake by the person who wrote the East coast release remains somewhat uncertain at this point. Earlier in this thread I posted photographs from some obscure west coast motorcycle magazines that show Spitfires. However, it's impossible to know if they are in stock form or already had been modified (in a couple of cases they are in ads for aftermarket parts, such as crossover pipes, so clearly those have been modified). Also, I have seen at least two 1957 Spitfires with faded blue tanks but, again, there is no way to know if these were their original tanks. The next photo is from an article about a particular racer published in May 1958, and it looks to me to be a silver 2-1/2 gallon tank.
[Linked Image]

As mentioned in the previous post, the February 1958 'Cycle' magazine has an article about the forthcoming 1958 BSA models, and about the Spitfire it says: "The Spitfire Scrambler will be continued exactly as introduced in the 1957 season... Finish is silver and chrome tank...". I am unaware of anything in print that points to other than a 2-1/2 gallon tank, although I cannot be certain whether at some point the west coast bikes might have changed to red. But, there is nothing to indicate they did, so using anything other than silver for my west coast bike isn't supported by any literature. A final point is that although BSA advertisements contain their standard disclaimer that specifications may vary between East and West, that doesn't mean they actually did vary.

Fuel Tank Size and Configuration

BSA used the same dies to produce the major stampings for the tanks of a number of different models, varying the locations of the fuel outlets, studs for straps, etc. to suit the intended application. The limited number of shapes is quite helpful when trying to identify a tank from photographs as well as when looking for one a particular machine.

I've already mentioned I determined that at least the initial batch of 1957 Spitfire Scramblers used 2-1/2 gal tanks. Beyond the volume of the tank, close examination of the following photograph shows it was of the configuration used on Clubman Gold Stars. Although having an external vent on a machine intended for use in the dirt might not have been be the best idea, the next photograph shows that the tank has both the hinged cap and external vent as used on Gold Stars.

[Linked Image]
From article in April 1957 'Motorcyclist' magazine.

My conclusion from all the materials I have been able to find is that at least the first batch of Spitfires to be delivered to the U.S. had the silver 2-1/2 gallon Gold Star tank with hinged cap and vent tube as shown in those initial press release/articles. Although I can't rule out the possibility that later ones were delivered with different tanks and/or colors, the only tank of interest here is that on the first Spitfire.

1964 A65 Lightning Rocket Tank

Thanks particularly to the restorer Ross Thompson, as well as to Gordo, Boomer and Mark Shearer in a series of posts in the Gold Star forum, I discovered that I already own a tank quite well suited for restoration/reconfiguration for this Spitfire. The tank is one that I've owned for so many years that I don't even remember where I got, and I now know is from a 1964 BSA Lightning Rocket. However, despite it being for an A65 and being manufactured after the last Gold Star had left the factory, the bottom of the tank is made with the same asymmetrical stampings with a recess on the right side for the throttle cable of an Amal GP as supplied on Clubman Gold Stars. The only difference between the bottom of this tank and one for a Gold Star is this A65 tank has the fuel outlets further forward, and the studs for the tank strap are further toward the back. Also, the top of this tank has a different fuel cap and lacks the external vent pipe. However, since the major stampings are identical, at the same time the dents in it are being removed it can be reconfigured to be identical to one that left the factory mounted on a '57 Spitfire.

[Linked Image]
Bottom of tank from a 1964 A65 Lightning Rocket. Aside from the location of the fuel outlets and tank strap studs, this stamping is identical to the bottom of a 2-1/2 gallon Gold Star tank.

The top of the following composite is an enlargement from the photograph in a BSA East Coast brochure, and the middle is the one used in the three magazine articles published in April and May 1957 that I discussed earlier in this thread. Although I wish the resolution were better, it is still sufficient in these two to reveal that the tank has the vent and the type of hinged fuel cap used on Gold Star tanks. Also, it can be seen that the magazine touched up the photo they used by removing the "bump" surrounding the hole for mounting the tank.

[Linked Image]
(top) From BSA East Coast brochure. (middle) From article in April 1957 'Motorcyclist' magazine. (bottom) Tank from a 1964 A65 Lightning Rocket.

The bottom of the composite shows my A65 tank over which is a yellow overlay that I carefully traced from the outline of the middle photograph. Where I could not clearly see the outline of the tank (i.e. at the front, and most of the indentation for the badge), I left gaps in the tracing. As can be seen from the slightly different perspective I should have photographed my tank from a position slightly further to the right. However, aside from this, the composite shows my tank is essentially identical to the one in the other photographs.

The only apparent discrepancies are that the tank in the middle photograph is slightly more pointed at the rear than is my tank and it is missing the bump for the mounting hole. However, both of these are due to how that magazine touched up this photograph. The bump can be seen in the top photograph and, although the contrast is too low to see the rear of the tank, a similar comparison I made with a photograph of a 2-1/2 gallon Gold Star tank provided by Gordo showed my tank and his are identical. Also, the resolution in the two other articles is even worse than the one I used in the composite, but the rear of the tank can be seen in one of them and it is identical to the A65 tank. That is, my analysis shows BSA used the same dies to stamp this A65 tank as they used for Gordo's Gold Star tank.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/29/13 12:18 pm

The composite photograph in the previous post shows that after repair, reconfiguration, and rechroming the tank that started life on an A65 will be an exact Gold Star tank for my restoration. However, repairing it only will be possible if the metal is in good condition, so I inspected inside the tank with my borescope. The following photograph shows a small region in the "pocket" at the left, rear where the design of the tank makes it most likely to collect water and fuel residue. The region at the left of the photograph is the bottom of the tank, and at the right is the side.

[Linked Image]

If you aren't used to examining metals with a microscope you might think that the inside of the tank looks bad, but actually it is quite good. The magnification of the borescope image depends on the distance of the end of it from the object so I can't put a precise value on it for this photo, but it's somewhere between 3x and 5x and with a resolution of ~0.3 mm. For comparison, I also used my borescope to photograph the outer wall of a piece of new EMT conduit at approximately the same magnification:

[Linked Image]

The ridges on the surface of the EMT have a spacing of ~1 mm but the undulations are so slight the tubing is shiny and feels almost smooth to the touch. Basically, the borescope shows the metal on the inside of my A65 tank is in nearly as good condition as a new piece of EMT tubing, with only patches of discoloration and surface rust, so this tank is an excellent candidate for restoration and reconfiguration into a Gold Star tank.

Tank Decal

I can only speculate on the following, but my guess is that the "flying Spitfire" tank decal was not introduced in 1957. This limited production, race-only model entered the lineup months later than the rest of the range so there would have been less time and motivation to tart it up with a special decal. However, the next year's A10-based version had become a standard model in the lineup by then so a decal would have it conform with the other machines in the lineup.

[Linked Image]

Addendum: Service Bulletin No. 15 from Hap Alzina, dated November 13, 1958 lists eight "varnish type paper decals" that they "obtained from BSA." Remembering that the Gold Star scrambler was given the name "Catalina" starting with the 1956 season, part number 42-8109 is a "Catalina Scrambler decal. Also listed are small and large "Super Rocket tank decal," which was another new model for 1957 (U.S.-only that year). More to the point, part number 42-8112 is a "Spitfire Scrambler decal (Picture of scrambles rider in action)." This is fairly strong evidence that as originally supplied in 1957 these bikes did not have decals on their tanks, which only began being applied to the machines sometime later.
Posted By: 57Spitfire

Re: 1957 BSA Spitfire Scrambler - 08/30/13 12:17 pm

Mag:

I am nearly at the same stage of restoration with my 57 Spitfire Scrambler, engine no. CA10SR.201. Lucky for me it was my dad's bike. He was the second owner since 1962. Unluckily, he let is sit out in the elements for 20 years before I rescued it. The cylinders had been blown two different times and it looks to have been crashed a couple times - broken motor mounts, crushed tool box, bent front pegs, etc. But, aside from a bad spray can paint job and someone bondoing in the badge mounts, it is all original. Your thread has been really helpful in identifying the bike and a proper restoration. I just got the magneto and generator back from Mickey Peters who did a great job on both. He also added a custom rubber seal to the clutch plate that will help with the typical oil leak problem there. He even plated the generator body back to the original gold color. Also he added an auto advance, which while not original, doesn't show and is a great improvement for starting. I look forward to more of your posts.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/01/13 2:22 pm

Originally Posted by 57Spitfire
Your thread has been really helpful in identifying the bike and a proper restoration.
Thanks very much for your response. My goal has been to put everything I could find on this bike into one place so the few people who have one would finally have a comprehensive reference source for information.

Although it is about a very specific model, the process I've followed is broadly applicable. However, this thread isn't like most other restoration threads here and I was beginning to think no one was actually reading it. So, again, thanks for your response.
Posted By: Boomer

Re: 1957 BSA Spitfire Scrambler - 09/01/13 3:53 pm

Great thread, we've just been reading and waiting for more from you! I've got a question. You say the frame is a GS frame. Maybe you can enlighten us on the difference between an A10 frame and a GS frame excluding the stamped bend for the oil pump clearance.


Bill
Posted By: Rickman

Re: 1957 BSA Spitfire Scrambler - 09/01/13 4:11 pm

Bill,
The only items I can see, to answer your question, although I will leave the actual response to MM, are these:

There are no muffler mounting loops? Passenger foot peg mounts?

And I notice the central gas tank mount seems shortened or cut down? In the early pics anyways...
I have an A10 frame myself, that seems to have this cut down form as well...

It aso seems that there are no provisions for any kind of chain guard... Single or four piece.
Brett
Posted By: Boomer

Re: 1957 BSA Spitfire Scrambler - 09/01/13 5:35 pm

Brett

I'm aware of most of the different configurations on the pe-unit swingarm frames, I just thought MM might make it clear to the many what makes a GS frame special.

Bill
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/02/13 12:37 am

Originally Posted by Boomer
I'm aware of most of the different configurations on the pe-unit swingarm frames, I just thought MM might make it clear to the many what makes a GS frame special.
You definitely should jump in here with this information. Otherwise it will be at least three weeks before I could put together anything on frames beyond just the diagrams in the BSA Service Sheets.
Posted By: 21inGoldie

Re: 1957 BSA Spitfire Scrambler - 09/02/13 6:45 pm

thank you magnetoman!
I have a couple of A10 spitfire scramblers one a 57 with matching 100 numbers. Great thread and thanx for info and pictures!


21"
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/05/13 6:28 pm

Originally Posted by 21inGoldie
thanx for info and pictures!
I hope the information assembled here helps as many owners of these bikes as possible. The next installment will follow shortly...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/05/13 6:30 pm

-- technical problems --

The 'preview' shows my post as it should be, but when I submit it all I see is a blank post. I tried twice with the same result, so will give up for now and try again later.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 09/05/13 11:05 pm

Magnetoman, a while back, in the shout box, Allan Gill mentioned that if you use the drop-down menu below the message box, and then select USING HTML and UBBCode your posting will appear. Morgan replied that HTML will never be turned on, due to security reasons.

I was getting blank postings, so I tried what Allan suggested. I figured that I couldn't hurt anything if Morgan has his settings the way he wants it. Anyway, it worked for me. Coincidence?

In any case, especially if you have a lengthy post, it is wise to copy it to your clipboard and perhaps even paste it into your word processor package (like MS Word) before you hit the Submit button. That way, if you hit a glitch, you can simply paste it into the forum post box on your next try. It helps keep your blood pressure under control.

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/05/13 11:26 pm

Originally Posted by TR6Ray
I was getting blank postings, so I tried what Allan suggested. I figured that I couldn't hurt anything if Morgan has his settings the way he wants it. Anyway, it worked for me. Coincidence?
We'll see if it was a coincidence a few seconds after I hit 'submit'. I've been uploading posts the same way for the past two years without this particular problem before, and the post I submitted a couple of minutes before was just fine. Anyway, if this one works, I'll try uploading the next installment again.

p.s. I submitted this post with the default "Using UBBCode," as I've done with all other posts. It appeared without problem. I then cut/pasted the following post from the Word document and tried to post it the same way. All that appeared was a blank post. I then tried again by changing the "markup" box to "using HTML and UBBCode" and, as you can see, it appeared.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/05/13 11:28 pm

Carburetor Alloy Distance Piece

I made an interesting "discovery" about the Carburetor Alloy Distance Piece 65-2562 listed for this model in the 1958 Hap Alzina Bulletin. The next photograph is an enlargement from one of the magazine articles that, as I've already discussed, evidence strongly indicates is one of the initial production models, and could even be the actual machine that I own. I've marked in yellow several reference positions on the engine, carburetor and frame:

[Linked Image]

I next used Photoshop to overlay a photograph of my machine that I took from approximately the same perspective and then scaled to the same size as the magazine photograph. The composite below shows the yellow reference marks from the 1957 photograph coincide very nicely with the corresponding features on my own machine.

[Linked Image]

Note, however, that I did not have the 1" distance piece installed when I took this photograph. This image analysis clearly shows that the machine photographed in 1957 did not have that distance piece either (or the drip shield).

Another discrepancy is a Hap Alzina press release shown earlier in this thread says the engines in these machines were supplied with high lift camshafts (H) and high compression pistons (HC) so following usual BSA practice mine "should" have HHC stamped under the engine number, but it does not. I am aware of several later ones that do have HHC stamped. Such discrepancies are consistent with it taking a while before the build specification became standardized on this model, which perhaps shouldn't be surprising given its introduction outside the normal planning process. In any case, even though the Hap Alzina bulletin issued 18 months later lists the distance piece, as mentioned earlier in this thread the configuration of machines shipped prior to any such revision to the specifications that took during 1957 would not have been reflected in such a bulletin. My conclusion from the evidence is that the engines on at least the initial batch of machines shipped to the U.S. did not have this particular piece. Luckily, in this case since I already have it the distance piece would be trivial to add it to the bike in the future if some new information ever came to light indicating it actually should be present. As an aside, I hunted for years before I found that distance piece, and was very happy when I did. Now I've decided it should not be on this particular machine. Sigh…

90% of the Time, 10% of the Restoration…
In most restorations you can count on the final 10% of the work requiring 90% of the time. In this one, the initial work feels like it has required 90% of the time. Things that are normally just taken for granted, like knowing the color of the tank, took considerable time to research. This doesn't even count the "dead time" of waiting years for one of only ~400 gearboxes made over a half-century ago to show up for sale. But, finally, I believe that just about everything that can be known about a 1957 BSA Spitfire Scrambler, is known, and just about all the uncommon parts for it that can be found (except the exhaust pipes), have been found.

What About Unknown Unknowns?

If the carburetor distance piece and the drip shield were not on the initial machines shipped to the U.S. as my image analysis indicates was the case, it raises the question of possible unknown unknowns. Since this particular difference was not documented in the 1958 Hap Alzina bulletin, might there have been other differences? Unless additional documentation comes to light, that will remain an unknown unknown.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/12/13 4:20 pm

Restoration Decisions

Before I had decided on an as-originally-built approach to restoring this BSA, I acquired some parts that I now don't plan to use on this machine. Specifically, I prefer the look of the alloy scrambler tank and the shorter "racing dualseat," both of which are used on the Gold star in the following advertisement, as well as the crossover high pipes introduced on Spitfires in 1959, but which were available as aftermarket accessories as early as 1957:

[Linked Image]
Factory brochure for the 1961 Competition Model Gold Star (also known as the All Sports).

[Linked Image]
Advertisement from February 1958 issue of Southern California Motorcycle News.

Because for the first few years after getting it I had intended to restore this machine to a period-correct "as-raced" (as opposed to "as-new") condition, I have a beautiful alloy tank, a new short seat, and a set of factory high pipes sitting on the shelf. Also, the timing covers of these machines have blanked-off holes for a tachometer drive, and my Spitfire came to me with just such a drive attached to it, so I also have a Smiths RC83 chronometric tachometer waiting on the shelf:

[Linked Image]

Finally, during the 1990s I picked up one of the rare dual-carburetor A10 heads. This would be a period-correct upgrade for the Spitfire since they were used on earlier A10s and since BSA lists it in a speed equipment catalog. At $123.94 including the necessary manifolds, it was an expensive performance item at the time:

[Linked Image]
BSA Accessory and Speed Equipment Catalog, 1960.

[Linked Image]
BSA (East) Bulletin. February 25, 1964.

If I did use this head, a pair of TT carburetors would be an appropriate complement given that they are listed as approved speed equipment for the Spitfire in a 1957 Hap Alzina bulletin:

[Linked Image]

I already have a 1-3/16" Amal TT so only would need one more (at the trifling cost of ~$400 they are selling for these days). For what it's worth, the TT that I have is mounted on a BSA C11 engine that has been decorating my office for the past 25 years:

[Linked Image]

While I acquired these "period-correct" pieces in the 1990s, my intention for over a decade has been to restore the machine to a condition that is as original as possible. However, even if I did use these "incorrect" parts (which I won't) they could be easily swapped for the proper ones in only an hour or two (although swapping heads might take a bit longer).
Posted By: Peter R

Re: 1957 BSA Spitfire Scrambler - 09/19/13 1:38 pm

MM, I admire this very well documented restoration, and attention for details.

In particular the frame/headstock repair is a first class job.
When I saw your first pics of the frame, I simply could not imagine that there could be the remotest chance of success, but I was wrong, and it proves (again) that almost anything can be achieved by dedication and competent craftsmen.

I look forward to watching your progress.

Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/19/13 8:22 pm

Originally Posted by Peter R
In particular the frame/headstock repair is a first class job.
Thank you for the kind words in your post. Indeed, almost anything is possible with the right tools and expertise. In this case I was lucky my friend possessed both when I needed that frame brought back from the dead 20 years ago.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 09/20/13 9:00 am

This section seems to get at least a couple of REALLY good ongoing build threads every year; this is another one of those.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/21/13 11:29 am

Originally Posted by GrandPaul
This section seems to get at least a couple of REALLY good ongoing build threads every year; this is another one of those.
Thanks very much for the comment. It's nice to know the effort is appreciated. I was traveling this past week but should have the next installment uploaded later today (although it will be a bit of a digression from actual welding and bolting).
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/23/13 11:52 am

I wrote in my first post in this thread that I will "… describe an approach to restoring a motorcycle that not everyone will want to copy." Although the "as-original" approach to the restoration that is documented in previous posts is basically what I was referring to, it goes deeper than that.

Museum Quality Restoration

When the term "museum quality restoration" is used to describe a motorcycle it's usually to try to make it sound better than it probably is. But, what do actual museums do when restoring something for their collections? Not that I'm in any way equating my BSA Spitfire to a priceless work of art, but my approach to this motorcycle has more in common with how an art museum's conservation lab approaches a restoration than with how a motorcycle shop does. Before getting to that, the 9 August 2013 issue of The New York Times has an article about restoring the world's first Duesenberg:

Three years and some 10,000 hours of intensive restoration work later … At what must be that shop's labor rates, this restoration would have cost at least $1 million. Describing the work the article says:

Typical of the era, the Castle coupe … was produced as a running chassis without a body. … The coupe’s aluminum-skin body used an ash frame. ... "Today, the whole restoration philosophy is about preserving as much original content as possible," he said. "From Day 1, that was our objective." … took apart the frame, removing hundreds of tacks and nails and replacing rotted sections with new wood. For strength, the structure was infused with epoxy.

Everything is fine up to the last sentence. However, any museum conservator would wince when reading that they infused the original wood with epoxy since it will be impossible to reverse that action when the epoxy starts decomposing as well as attacking the cellulose in the wood. Epoxies are especially problematic because their final properties depend on both the mixing of the components as well as the details of the curing. No matter what, the final epoxy compounds are not incredibly stable on long time scales. "Preserving as much original content as possible" on any restoration is an admirable goal, but it also needs to be done using materials and techniques that do not seed the slow destruction of that original content. The article continues:

"Our job was to deliver the car as new." … The four known photographs of the car in its original condition were taped above his workbench. … devoted hours to research… Ignoring the obvious, that when "as new" the Duesenberg factory did not use epoxy-impregnated wood in its construction, reference to two paintings will show how art museums deal with objects that require restoration and about which not everything is known.

Hans Holbein the Younger was one of the most significant artists of his period (early 1500s), and his "French Ambassadors" was one of the most significant paintings of its time because it was the first example of the appearance of an anamorphic feature. This feature is the angled "blur" across the bottom of the painting, shown below in its unrestored form in the early 1990s.

[Linked Image]

If that blur is viewed at a grazing angle it looks like the following, which shows that the feature is a skull:

[Linked Image]

However, as can be seen, a significant amount of paint in the central portion of the skull's face was missing at the time. In order to restore this painting, the first task of a museum's conservation department was to determine as best as they could where new paint needed to be applied to reproduce as accurately as possible the painting as it originally was when it left the artist's studio (despite, obviously, not having a photograph showing what it looked like in 1532), and next to use materials and techniques that later could be reversed without damaging the original in any way at all if new information becomes available that indicated their original restoration decisions were in error.

An analogous decision in the case of a motorcycle would be not to polish the engine cases to a mirror finish since the sand casting marks could not be put back on again later. In the case of the painting the restorers were working on a truly priceless work of art in the National Gallery of England so they not only approached this restoration in the most thorough manner possible, they also documented all of their decisions and restoration work so that later scholars acting in light of new information can see where they might have made mistakes in order to correct them. This painting was restored in the 1990s and the museum published a detailed book in 1997 documenting everything about the painting and restoration process.

The bottom of the next composite shows a painting in the Louvre as it appears in the infrared. This "IR reflectogram" reveals the extent of the restorers' work since the paints they used have different IR optical properties than do the original pigments. In this case the painting is of considerable interest because it is by someone who was one of the most important of his time (Sassetta), but it was too damaged to exhibit in as-found condition. As can be seen, no detail even remained of the staircase so that feature had to be entirely reconstructed using the best judgment of the restorers based on their knowledge of the painter's style and practices. This example is analogous to the case of restoring a motorcycle as accurately as possible when its condition is too poor or incomplete to leave it as-found and at the same time there is very little information about its configuration when new. That is, like the motorcycle delivered to me in a box in the first post of this thread.

[Linked Image]

Whether any motorcycle merits it or not, the approach I've taken with this 1957 BSA Spitfire would be familiar to an art museum conservation expert. This wasn't what I had in mind when I started, but two significant involvements with the museum and art worlds beginning in the late 1990s heavily influenced my plans. As a result, my goal has not been to "restore" it to a shiny, powder coated, highly polished condition with upgraded aftermarket parts to create what many motorcyclists refer to as "museum quality," or as others state without any foundation to their claim is "how the factory would have made it if producing the machine today." Rather, it is to have a motorcycle that is as close as possible to how it was when it left the factory. In other words, to restore it in a way that conservators in a museum would recognize as an appropriate way to have proceeded.

As examples of the consequences of this approach, pre-painted Gold Star tanks complete with badges and fuel caps are available from India for less than $600 delivered. Even if those tanks were reasonably made, properly chromed, painted well and fit without problem, and even though the tank I am having refurbished right now will cost at least twice that by the time it is ready to install, a "museum quality" approach dictates spending the additional money. Although use of various perfectly reasonable aftermarket parts could save me many hours of work restoring original BSA parts, I have avoided using such aftermarket parts to the extent possible and instead have been putting in the necessary many hours of work.

Different disciplines vary somewhat in their standards and approaches, and even then any number of decisions have to be made by a restorer based on specific aspects of an object itself. So, in addition to painting and sculpture conservators at the Getty, Guggenheim, and Metropolitan art museums, over the years I've had opportunities to discuss my approach with restoration experts at the National Air and Space Museum, the Henry Ford Museum, the Science Museum in London, and others. I should add, though, that while approaching a motorcycle restoration this way might sound completely unwarranted, or unnecessarily complicated or time consuming, it's really not a tremendous amount of extra work. Extra money and work, certainly, but not tremendously much more so.

Finally, if this were my only motorcycle, or if there were a worldwide shortage of BSA A10s, restoring one in the way I am doing it that won't be ridden much might be an issue. Neither is the case, so it's not. Also, if in the distant future (far, far distant future, I hope) a subsequent owner decides to use it in off-road competitions they won't discover a "restoration" that is only skin deep like so many are since I will be doing a complete mechanical restoration as well. Still, when done, it is unlikely that I will ride it very much. For the street, lack of lighting means it can't be licensed, and for the dirt, my Honda XR650L is 50 lbs. lighter with the same h.p., much greater suspension travel and, um, well, an electric starter.

Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/28/13 12:39 am

Fuel Tank Update

Thanks to input from Boomer and Gordo, earlier this summer I was able to identify an early A65 fuel tank I've had for years as having been stamped from the same dies as used for Clubman's Gold Star tanks. As a result, my dented tank is now spending the fall in Canada with Ross Thompson. After he is finished reconfiguring and restoring it he will send it to Brown's Plating in Kentucky and finally, after its tour of North America, many weeks and many, many dollars from now a perfect Gold Star tank for my Spitfire will be returned to me. Well, not quite perfect, since it still will have to be painted before it's ready for use on my Spitfire.

Sending Parts from the U.S. to Canada

In case you need to do it, sending parts for repair in Canada is fairly easy and not horrendously expensive if you use the US Post Office rather than UPS or FedEx. Basically, you have to set up an account on the USPS web site, which is very easy to do. Then elsewhere on the USPS site you enter the weight and dimensions of the package, at which point you will be given the option to ship it in 1-3 days for a lot of money (Global Express Guaranteed), or in 3-5 business days for about half that (Priority Mail Express International). I used the latter and my tank was delivered to Ross in Ontario on the 7th business day.

The USPS site leads you through all the steps, one of which is to enter the relevant shipping information. To avoid Customs duty it is essential to write something like "Antique motorcycle part to be repaired in Canada and then returned to U.S." Although the site makes it sounds like everything can be done on line, once you print the forms you will find you are missing the clear USPS envelope needed to hold the forms on the side of the box. Even if you had one of these envelopes, it looks to me like you still would need to take everything to the nearest post office for them to do a few more things to it. At least, that's what I did. However, having typed in all the forms on line not only saved me from having to write everything by hand once I got to the post office, possibly with mistakes, it also gave me a 10% discount on the shipping cost.

Office supply stores carry boxes in a wider range of sizes and of heavier construction than you can find at stores dealing with moving supplies (e.g. U-Haul). I double-boxed my tank and used plenty of packing material as well. The total weight ended up 14 lbs. and the cost to ship it to Canada was $65.

Another Appeal for Several Parts for this "Historic" Restoration

As mentioned several times in this thread, I've managed to collect nearly everything needed to restore this machine to the configuration it had when it was the very first one to roll off the assembly line in February 1957. When I started this thread I was still missing four significant items. However, since then I found the correct "/89" carburetor on eBay; thanks to several contributors to BritBike Forum the fuel tank has been crossed off the list; and thanks to the wonderful generosity of one of the readers of this thread the Competition Number Plate also has been crossed off the list. This leaves the bike needing only the:

Exhaust pipes (42-2797 right; 42-2799 left)

Although I could fabricate the pipes, given this machine's "historical significance," I would like to have the highest percentage of original components on it as possible. If you know of anyone who has a set of these they might be willing to sell or trade (I have a fairly rare ASCT gearbox I no longer need), please send me a PM or an email to [email protected]

Intermission

[Linked Image]

At this point I've basically returned this Spitfire Scrambler to the condition Swan and Bry started with when they began their now-completed Gold Star and Velocette restorations:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=483360#Post483360
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=217887#Post217887

Since it subsequently took them 2-3 years to transform their machines, it likely will take me at least that long once I am able to start concentrating on this bike. As I wrote in my first post, "[this thread is] going to be in two parts, possibly with an extended intermission between them." It's time for that Intermission, but I hope to resume with Part II in a few months (although there might be a few minor updates between now and then, depending on my progress with other projects I have under way).
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 09/28/13 1:43 am


That was a really interesting read. Thanks for taking the time to post.

Rod
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/29/13 12:06 pm

Originally Posted by Redmoggy
That was a really interesting read.
Thanks very much for the comment. But, the story isn't anywhere close to finished, so there will be more to come. Finally having all the parts (except exhaust pipes) collected, and the documentation for what the configuration should look like gathered in a coherent package, provided a convenient place to pause.

I spent four hours in the garage yesterday moving motorcycle stands and boxes of parts around and straightening up to prepare for another project that has been gathering dust for as long as the Spitfire. After I build up some momentum with it both projects then will be proceeding in parallel.

Pulling two bikes to pieces at the same time normally isn't a good idea but it shouldn't be a problem as long as I keep things well organized. Or so I'm telling myself...
Posted By: L.A.kevin

Re: 1957 BSA Spitfire Scrambler - 09/30/13 1:17 pm

You are a brave man to be doing two projects at once. I'm too chicken to even try. Just finishing up a WM20, and my poor Dominator is languishing waiting for it's newly reubilt KF2C. Then, there's the Guzzi Lemans that needs a head gasket, the MZ that needs a chain and oil change, the Guzzi Quota that needs tires, and so it goes...

Soon as the M20 is done, I'll give the rest of 'em love. That's what I tell myself.

Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/04/13 11:45 pm

Originally Posted by L.A.kevin
You are a brave man to be doing two projects at once.
In that case, I won't mention the third...

But, back to the Spitfire, a minor bit of progress to report was finding another quick change hub as a backup. The sprocket on the hub that came with mine is worn so I will need to weld on a new one. That "only" will require machining the old one off the hub, machining the ID of a new one to match (after first finding a new sprocket with the correct no. of teeth), welding the two pieces together, then turning the drum to remove any distortion induced by all of the above. I wanted a backup hub in hand before starting this surgery in case things turn ugly...
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 10/07/13 8:00 am

Hi magnetoman
A very interesting read, I just bought a 57 spitfire from a man in utah and currently waiting for it to be delivered to the uk. It looks to be pretty much complete how ever the man i bought it from said he cant find the vin number i won't no if it is there or not untill i get the frame cleaned off ready for paint but is there a way of finding the correct number that matches the engine
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 10/07/13 12:47 pm

Quote
but is there a way of finding the correct number that matches the engine


Both the VMCC and the BSA owners club will not release this info, they will just say if the bike left the factory with those numbers or if its a mixture. The reason is to stop people who have mismatching engines/frames from restamping them to make them match.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 10/07/13 2:34 pm

Where should the number be
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/07/13 3:10 pm

Originally Posted by kommando
Both the VMCC and the BSA owners club will not release this info, they will just say if the bike left the factory with those numbers or if its a mixture.
This is what I do as well with my set of production records.

Originally Posted by paul67
Where should the number be
Look at the last photo in the following post:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=498504#Post498504

Please post a few photos of your Spitfire when it arrives in England.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 10/07/13 3:22 pm

I see on the head stock, i will look for it when it gets here. I do have a photo but not a good one i will see how to upload it
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 10/07/13 3:51 pm

i cant see how to upload photos
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/07/13 3:54 pm

Originally Posted by paul67
i cant see how to upload photos
There are tutorials explaining how to do that, such as at:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=169660&an=31#Post169660
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 10/08/13 11:48 am

[Linked Image]
mostly complete eng no CA10SR-3** and the correct gear box SCT2
just needs a bit of love. When i get it back i will take a few better pictures
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/08/13 5:43 pm

Very nice. The seat is a particularly fetching performance modification...

You have a nice project ahead of you.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/10/13 10:56 pm

A few pieces of your scrap aluminum could be of great help with this project. What I'm hoping to find is described at:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=509847#Post509847
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/13/13 9:05 pm

I made some progress today. Both footpegs were bent down from the weight of the riders over the years, as can be seen in the upper photo of one of them in the next composite:
[Linked Image]

Unfortunately, it's not as simple as bending upwards the portion of the foot peg that goes into the rubber. If you look at the casting mark in the upper photo you can see that it is basically straight, which means the fore-aft portion of the assembly has a twist in it (the other foot peg had the same problem).

To eliminate this twist I machined two "clamps" that are 1"x2"x6" as shown in the next photograph.
[Linked Image]

I used Al so it wouldn't mar the steel, and made them with ample cross sections to withstand the force of the press. To deal with the irregular cross section of the castings I machined slots wide and deep enough (~1/2" wide x ~1" deep) for them and then tapped 3/8"x24 holes in each to take up the slack. I inserted brass shims between the bolts and the footpegs to keep from marring the surfaces. Also, I offset the bolts in order to apply the twisting force to the foot peg at points as far apart as possible, i.e. for maximum torque.

The next photograph shows one of the foot pegs mounted in my press ready to be bent back into proper shape.

[Linked Image]

The various twists and turns plus the irregular cross section of the foot peg complicate matters, but three large C-clamps held everything while the press applied the necessary pressure. However, it was impossible to hold one part of the assembly perfectly stationary while applying force to another, as well as impossible to see how much of a bend remained while it was clamped in the press, so it required two tries for each foot peg to achieve the result shown in the lower part of the composite at the top of this post.

One task closer to the finish. Only 976 (estimated) tasks left to go…

Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 10/22/13 12:49 pm

did they make a parts book for this bike
Posted By: Peter R

Re: 1957 BSA Spitfire Scrambler - 10/22/13 4:58 pm

A complicated way to do a relatively simple job imo.
Applying some heat with an oxy-acetylene flame would probably lead to the same result.
However, your end result looks ok, and that's what counts. :bigt
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/23/13 2:06 pm

Originally Posted by paul67
did they make a parts book for this bike
If they did, I've not run across it in the past 20 years of looking. The Alzina supplemental parts list I posted earlier in this thread, along with the A10 and Gold Star parts books, are what I use. The text on the Alzina list strongly implies that there is no separate book.

Originally Posted by Peter R
Applying some heat with an oxy-acetylene flame would probably lead to the same result.
Maybe yes. I have an oxy-acetylene torch so it's not that I didn't consider using it, but the advantage of the way I did it is it allowed a slow, controlled return to the original configuration with minimum chance of accidentally distorting the arm in a second plane.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/03/13 8:29 pm

Only some minor progress to report on the Spitfire. The head has a few chipped and partially missing fins that I'll deal with soon by building back up with TIG and then reshaping and re-texturing them. However, since I don't weld every day, first I want to get my skills fully up to speed since this work requires a finer touch than connecting two chunks of 6061. A good analogy to TIG skills might be riding a friend's highly modified modern bike. For me, at least, it takes some time before I can ride such a bike at more than 70% the level I will be after an hour on it (riding a modified Aprilia SXV 5.5 for several hours around N. Calif. last week made me think of this analogy -- at 70 h.p. and 270 lbs. for the stock bike, with no discernible flywheel, it's not like riding a Gold Star).

Anyway, I've already tested cleaning procedures and several possible filler rods (4043, 4047, 4145 and 5356) and electrodes (ceriated and 1.5 and 2% lanthanated) using a broken Triumph gearbox cover, refreshing my skills at the same time. Further, after boiling for an hour, cooling off on my barbeque right now is a large tub of soapy water holding a head and right side engine case from an A65 (thanks KC in S.B.!) and a K2F magneto housing (thanks MikeG!). The head even came with a few pre-broken fins so I won't need a hammer to simulate the one on my Spitfire.

Other things continue to intrude on my time this fall so progress on this bike will remain slow for a while longer.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/07/13 7:35 pm

I posted on September 28 that I had just sent my A65 fuel tank to Ross Thompson in Canada to repair and reconfigure into a proper Gold Star tank. Earlier this week he sent me a half-dozen photos of the finished tank. As you can see from the following 'before' (a lot more dents were in it than are apparent in this photo) and 'after' (in place of the now-missing dents are a G.S. cap and vent) photographs, Ross has transformed it into a thing of beauty:

[Linked Image]

It now travels from Canada to Brown's Plating in Kentucky for polishing and plating, and then finally back to me after completing its extensive (and expensive) tour of North America.

On another note, my magneto restoration thread just hit a milestone of sorts, passing the 20,000 views mark just 15 months after I started it. It required quite a bit time to write so it is gratifying to know so many people find this information useful.
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=446733#Post446733
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/11/13 10:05 pm

Making a long story short, although I have a 450 Amp TIG available, recently I bought a 200 Amp machine. The reason for this is the newer inverter welders have adjustable waveforms that make the arc much more precise and controllable than is possible with a transformer welder. This is especially useful for aluminum. Anyway, after researching the issue I bought the machine, gathered junk motorcycle castings (again, thanks KC in S.B. and MikeG), and have been experimenting with various filler materials and electrodes.

One of the reasons I'm pursuing this is I need to repair and/or replace several fins on my Spitfire Scrambler's head, and TIG is the way to do this. Also, I need the control an inverter TIG gives me for another project I've been working on for the past few months.

The A65 head KC in SB sent happened to have damage of both the repair and replacement types adjacent to each other on the top (actually, the bottom) and second fin:

[Linked Image]

I was experimenting with 4047 filler rod last week to see if its increased fluidity over the more standard 4043 would be helpful on castings and went further with that work than I had planned. This current post is a result of that work. I used a carbide burr to grind a channel in the top upper fin to be ready for welding in case I was able to bend it back up into the correct plane (it's not clear from the above photograph, but the cracked fin angles downward).

[Linked Image]

However, it snapped like glass, so I cleaned both freshly exposed surfaces with a wire wheel, clamped the fin in position, ground the channel a little deeper, and tack welded one end.

[Linked Image]

Not shown is I then tacked the left end, following which I filled the channel from right to left. Unfortunately, when I did this work I only had the 4047 in 1/8" rod, which was too large for for a proper repair but good enough for what I wanted to do with this experiment.

[Linked Image]

The too-large diameter plus the extra fluidity of the 4047 resulted in the weld being quite a bit wider than it should have been. But, hey, this is why I was experimenting on junk castings until I had determined the best parameters to use.

Despite the increased fluidity of 4047 I wanted to see if I still could use it to build up the missing material on the second fin. As you can see from the next photograph, doing this was no problem (although, with an extra blob at the left that probably wouldn't have been there had I used 4043). Much larger fins than this could be built the same way as I did this one, by laying successive rows of beads. In the case of interior fins building them up, rather than attaching broken pieces, is the only possibility.

[Linked Image]

At this point I had both fins of this junk casting filled in with TIG. However, an actual restoration would next require grinding excess metal away to give the correct profile, and then producing a realistic sand-cast texture in the now-smooth filler… [to be continued]
Posted By: Tiger100

Re: 1957 BSA Spitfire Scrambler - 11/13/13 5:12 pm

Not too shabby for a first attempt mate. I haven't used a TIG so will be keen to see your progress eh.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/14/13 10:41 am

Originally Posted by Tiger100
I haven't used a TIG so will be keen to see your progress eh.
Those welds were the result of me experimenting with a different filler rod on several areas of that casting and aren't the quality I would have had with a different filler material and a smaller rod diameter. If you're familiar with gas welding, think of a 200 A inverter TIG as giving you the pinpoint control of a #000 tip that has the heat output of a #4.
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 11/14/13 12:33 pm


My 66 Bonnie came with broken fins on the rocker boxes. Caused by someone fitting the rocker shafts with a sledge hammer. I was going to ditch them thinking that building up a fin that small would be impossible. I only have experience with a MIG. After a chat with a local fabricator i dropped them round to him. He returned within the hour and i remain astonished by the mans skills with a TIG. After a go in the bead blaster i can not make out the repair.

Keep up the good work!

Rod
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 11/14/13 2:22 pm

This is the technique I use to restore the original as cast look, you have to be careful with fins or you end up back where you started.

The trick to restoring the original finish is to place emery cloth on top of the dressed weld (ie smoothed back to original shape) and to use a hammer on the emery cloth, the rough finish of the emery cloth is transferred to the alloy. You need to practice on some scrap alloy first to work out which grades of cloth work, I find 60 works well but the finish did vary a lot on these castings, moving the paper around makes the pattern more random. I then follow up with nails of all sizes and use them to put random bigger holes, have a look at the casting to see if and how many of the bigger ones you need.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/14/13 3:54 pm

It appears the "standard" way vehicle restorers add a cast texture is it to hammer it into the aluminum using a piece of coarse sandpaper. On a different site a few months ago someone showed texturing being done this way, but with the help of a Hasting's Air-Peen hammer. This hammer has a ~4 mm dia. tip and uses 100-150 psi air to operate at 10~20 Hz. It looked to be a quite useful tool and it took me a few months to find one for myself:

[Linked Image]

For present purposes I just wanted to know if sandpaper worked for adding the appropriate texture so I only took the time to file away excess metal by hand near the left edge of the weld (rather than dragging out additional air tools and working on the entire weld). I then placed a piece of 60 grit sandpaper over this area and used the air hammer on the back of the sandpaper.

[Linked Image]

If I had polished more of the original fin material at the top and right of the above photograph to make it shiny it would be difficult at his magnification to see the difference between it and the "re-textured" surface along the edge of the fin where I had filed the weld to approximately the correct level. However, on closer inspection, or when viewed in different lighting, the "sandpaper texture" leaves a lot to be desired.

I then used my mill to saw off a large piece of fin to use for some initial texturing experiments. The next photograph shows the results on seven regions of the fin:

[Linked Image]

1. Undisturbed fin material. The 1/2-mm spacing between bars at the top shows the magnification. It isn't clear from this photograph but there is a "grain" to the undulating surface that runs from top to bottom. Also, the surface looks a lot like waves on a liquid that suddenly froze (which, in fact, it is);
2 The surface after preparing for welding using a stainless steel wheel in a die grinder (0.012" wire dia.). As can be seen, this removed all the texture from the original surface;
3. After using a stainless steel wheel in a Dremel (0.003" wire dia.). This removed the discolored oxidation from the surface and left it shiny but with the original texture intact;
4. After using a brass wheel in a die grinder (0.005" wire dia.). This removed the discolored oxidation from the surface and left it shiny but with the original texture intact;
5. After filing with a 10-inch second cut file. This is what the surface of a weld would look if the excess aluminum filler were removed with a file;
6. After filing with a 10-inch second cut file followed by 60 grit sandpaper applied with the air hammer.
7. After filing with a 10-inch second cut file followed by 60 grit and 100 grit sandpaper applied with the air hammer, finished with #00 steel wool rubbed in the direction of the grain.

Number 7 above looks like the best of these attempts, so it's shown again below adjacent to the original fin material.

[Linked Image]

Two principle differences are apparent between the as-cast surface and the "sandpaper texture": the spacing between the sandpaper indentations is too small, and the indentations are too sharp. Although the former could be changed by using a coarser grit than 60, the latter is fundamental to the use of sandpaper. Because of this, I've been pursuing several ideas for imparting a much more "cast-like" texture to the aluminum.

I've done quite a bit more with my inverter TIG welder since the experiments described above and I'm ready to reattach/rebuild the Spitfire's fins when it comes time for that. I hope to have a better solution than sandpaper for the texture problem before too long as well.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 11/15/13 9:53 am

Magnetoman,

Have you tried using a needle scaler (I think they are sometimes called a needle peener)? I'm talking about those air powered tools used for descaling and stress relieving a weld, or for removing rust in general from steel parts. I have no idea if it would work to stipple your aluminum, but it may be worth a try.

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/15/13 12:00 pm

Originally Posted by TR6Ray
Have you tried using a needle scaler... have no idea if it would work to stipple your aluminum, but it may be worth a try.
Thanks very much for the suggestion. Searching the web turns up three techniques for restoring a cast texture: media blasting, sandpaper, and needle scaler. I have all three but, unfortunately, I also have a magnifying glass.

Any way of creating a matte surface leaves the repair much less obvious than if it were left shiny. The question is, is any of them good enough? This then becomes an issue of individual judgment. It's not unlike repairing a body panel on a candy apple red car, then spraying the area with a can of red paint. At a glance the repair would be much less obvious than if left unpainted. But, would it be good enough? The answer to this might be 'yes' if the car were for regular, heavy use, but it would be 'no' for anything more than that.

The same issue arises when discussing whether stainless steel is a "good enough" substitute for cadmium (we're talking color and texture here, not performance). At anything more than a quick glance the use of stainless is obvious (nb. stainless, aluminum, cadmium, steel, and silver all look "silver," but they all have slightly different optical properties that distinguish them). Some people try to do better by sandblasting the stainless. Instead of a 1 sec. glance it now takes 1.5 sec.

Anyway, I'm exploring techniques to try to do better than the current "good enough." Given the relative crudity of all three techniques currently used, there's good reason to think I'll succeed. However, if I fail to find something that does better, I'll have to decide that sandpaper is "good enough."
Posted By: robcurrie

Re: 1957 BSA Spitfire Scrambler - 11/15/13 12:15 pm

The plastics industry uses acid etching to produce textured mould surfaces. There is also the laser etching process which I've seen produce bitmap images on tool steel!

Rob
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/30/13 1:06 pm

Originally Posted by robcurrie
... acid etching to produce textured mould surfaces. There is also the laser etching process...
I had to be in the Middle East for a week, returning home via something else in San Francisco, so I haven't made much progress on my Spitfire recently. I haven't had a chance to do anything about the texturing issue. Still, there have been a few small steps forward. My fuel tank arrived at Brown's Plating a week ago so it should be back to me soon. It still will need to be painted before it is finished. Also, the sprocket on the rear wheel hub is quite worn so before I left on this latest trip I ordered a 46-tooth steel sprocket to use as a replacement. It was waiting for me when I returned:

[Linked Image]

Sometime in the next few weeks I'll machine the old sprocket off the hub, machine this new one to fit, and weld them together. Since the number of teeth isn't divisible by either 3 or 4 I'll either grip the new sprocket from the inside using the 4-jaw chuck or use a faceplate to properly center it on the lathe. Precise concentricity is important for this so no matter what method I use it will require some time indicating off the base of the teeth.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/09/13 10:04 pm

Progress on my Spitfire these past few months has been slow, as I predicted it would be due to an oversubscribed schedule, but I made some very significant progress this evening. UPS dropped off my fuel tank. It came to me from Brown's Plating where it had been sent by Ross Thompson after he repaired it. It looks spectacular (thanks, Boomer and Gordo, for recommending Ross). I'll try to take a photo this weekend, although photographing a completely reflective object in a way that shows anything other than the space surrounding it isn't easy.

Of course, my only contribution to this progress was writing a couple of checks (figuratively speaking). But, in fairness to me, they were BIG checks. All it needs now is a vent tube and a pair of tank badges. Oh, and paint. But, hey, getting it painted can't cost all that much, can it?...
Posted By: robcurrie

Re: 1957 BSA Spitfire Scrambler - 12/10/13 12:17 am

Magnetoman, regarding photographing of reflective objects, in a studio I use a "light tent". Without access to a studio, you could use a white table with a white sheet suspended above it like a tent. The idea is to illuminate the tent from all around outside, so it would be good to do this outside at midday. You poke the camera lens through the smallest possible opening in the tent and the only reflection you might see is the lens.
Rob
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/10/13 1:13 am

Originally Posted by robcurrie
you could use a white table with a white sheet suspended above it like a tent...
Rob,

This is why I wrote that I would "try" to photograph it this weekend, rather than promising I would. Finding the material, then building a tent large enough for the tank, and then illuminating it reasonably uniformly would take quite a bit of time and effort. In the end there wouldn't be anything to see other than a shiny chrome tank that otherwise is pretty featureless. But, I'll try...

It's great to have the tank back after it having spent the fall touring North America. I still have to deal with the issue of paint before I can completely cross it off the to-do list.

Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 12/10/13 10:13 am

Just take it to the lightest colored room in your house with natural lighting through the window(s), and photograph it without flash on a light-colored surface.

It'll work better than you think!
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/10/13 10:47 am

Originally Posted by GrandPaul
Just take it to the lightest colored room in your house with natural lighting through the window(s), and photograph it without flash on a light-colored surface.
The difficulty with photographing it is because it's an excellent convex mirror. The kind of mirror that's in a convenience market that lets the clerk see the kid in aisle 3 shoplifting Twinkies.

The problem is to photograph a curvy mirror without having the distracting reflections of all the objects in the mirror. It's exactly like the problem of trying to photograph the 'Cloud Gate' sculpture in Chicago to show only the highly reflective surface without anything else:

http://en.wikipedia.org/wiki/Cloud_Gate

The only way to completely overcome this is to do as Rob suggested and tent the tank with translucent white. At this point only the less-distracting white is reflected, but it still requires tuning the lighting to accentuate the curves of the tank.
Posted By: Rickman

Re: 1957 BSA Spitfire Scrambler - 12/10/13 6:43 pm

So, wait until painted???
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/10/13 11:08 pm

Originally Posted by Rickman
So, wait until painted???
OK, OK. But, on the premise that not everything worth doing is worth doing well, here's a photo I took tonight without benefit of tent or proper lighting:

[Linked Image]
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 12/11/13 7:09 am

Nothing wrong with that photo. It shows the high quality of work carried out
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/11/13 11:12 am

Originally Posted by Allan Gill
Nothing wrong with that photo. It shows the high quality of work carried out
My reluctance to make a snapshot like the one I posted is because had I taken the time to do it as described by Rob Curie the result would have been so much better for showing the high quality of the work done on this tank.

That snapshot allows someone to judge the quality of the metalwork and plating of only ~10% of the surface of that tank. With proper lighting and composition it would be so much more impressive.
Posted By: RGSDave

Re: 1957 BSA Spitfire Scrambler - 12/11/13 12:02 pm

Tank Looks Great,When I Painted My Rgs Tank I Used A Metal Prep by POR 15(AP120)For Painting Over Chrome.GOOD Stuff.I Don't Know Why My Phone Caps Everything Dave
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 12/11/13 12:36 pm

Looks like a piece of artwork from here...
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 12/14/13 6:57 am

Hi Magnetoman, what type of magneto is on the the spitfire
mine is here in the uk now just waiting customs clearence but as its not run in a while the magneto probly will want rebuilding or replacing
Paul
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/14/13 10:34 am

Originally Posted by paul67
what type of magneto is on the the spitfire
As far as I can determine it takes a Lucas K2F. None of the other BSAs that year used a K2FC, which the 1957 Lucas catalog shows only having been used on the Triumph TR5 and TR6.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/26/13 3:15 pm

I finally found some time today to make a little progress. Thanks to the generosity of someone who has been following this thread, a couple of months ago the then-missing number plate arrived in the mail. Although he refused payment he made the mistake of having his return address on the package so I sent him a copy of my Gold Star book as a thank-you.

As you can see in the next photograph, someone had drilled two 1/4"-dia holes near the bottom of this number plate.

[Linked Image]

Today I removed the paint from around the holes and clamped it to my welding table. What isn't apparent in the next photograph is that there is a 1/2"-dia. hole in a block of Al directly under the 1/4" hole, with the rest of the number plate in good contact with the block to minimize warping.

[Linked Image]

I used Si-bronze TIG brazing rod as the filler to further reduce warping, since it melts at a much lower temperature than steel. I set my power supply to 100 Amps but probably didn't have the pedal depressed more than half way.

[Linked Image]

Although silicon-bronze melts at a much lower temperature than steel it still is quite hard. To save time grinding and filing I milled both sides of each repair 0.005" above the height of the number plate.

[Linked Image]

A few minutes with a file on each side of the holes followed by two grades of Scotchbrite pads in a die grinder has the plate ready for painting (after removing the rest of the old paint, of course).

[Linked Image]

So, that's one more thing crossed off this restoration's to-do list.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/02/14 12:24 am

The Spitfire is now at least 99% complete and ready for the final push to restoration. Because of this, for the past few weeks I've spent most of my free time on another machine that I've been restoring in parallel. Like the Spitfire it, too, was a work in progress for the past two decades, but this past year I ramped up the activity on both by a few orders of magnitude. It takes quite a bit of work to document a restoration like this so I haven't decided yet whether to do it with this second bike.

Anyway, the only real progress with the Spitfire was the arrival last week of the tank badges and mounting clips I ordered from England.

[Linked Image]

Originally Posted by RGSDave
Tank Looks Great,When I Painted My Rgs Tank I Used A Metal Prep by POR 15(AP120)For Painting Over Chrome.GOOD Stuff.
I missed this post when it first appeared and kept meaning to reply since then. I'm actually thinking of painting the tank myself, so I am very interested in suggestions like this. Thanks for the comment.
Posted By: robcurrie

Re: 1957 BSA Spitfire Scrambler - 01/02/14 12:58 am

Magnetoman, a word of warning about the badges, I have read a few of horror stories about new badges cracking soon after being installed. Please do some research about this before you fit yours.

Rob
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 01/02/14 6:58 am

MM, sure you will have read it but just in case.

My new tank badges cracked !

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=514657#Post514657
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/02/14 11:56 am

Originally Posted by robcurrie
Magnetoman, I have read a few of horror stories about new badges cracking soon after being installed.
Originally Posted by kommando
My new tank badges cracked !
Thanks for mentioning this. Given that these little pieces of plastic are $50 for a set, I made a mental note of this problem when it was raised in some other thread recently and have been thinking of possible ways to deal with it. One possibility would be to machine tiny "top hat" shaped inserts slightly thicker than the badges to keep the clamping force from being applied to the plastic. Another would be to reinforce the backs with epoxy and/or metal to spread the clamping force over a much wider area than just the screw holes themselves. Both cases also would benefit from bits of foam or rubber in the right places to damp vibrations. But, I like to learn from observations like yours, so no matter what solution I come up with, I promise it won't be to simply attach the badges directly to the clips and then cross my fingers.
Posted By: Bry

Re: 1957 BSA Spitfire Scrambler - 01/02/14 2:05 pm


Hi Magnetoman, I encountered a similar problem with tank badges cracking at the screw holes on my Venom. On the replacement set I hand reamed out the screw holes to clear the OD of the screw heads. I then turned up a disc from thin aluminium plate the same diameter as the OD of the badge and epoxied this to the rear face of the badge. Holes for the screws were then drilled in the plate at the locations of the originals. Clamping force and localized screw head pressure is then only applied to aluminium plate so no risk of cracking the badge.

BTW - Great work on the restoration and thanks for the excellent detailed account in this thread, I am enjoying reading about the research and progress very much.

Bry
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/02/14 8:22 pm

Originally Posted by Bry
I am enjoying reading about the research and progress very much.
Thanks very much for the nice comment. As you well know it takes additional effort to pause at appropriate times in the middle of a job to photograph it, and more time yet to document the work, resize the photos, and upload them. A supportive comment like yours, especially from someone who does such nice work himself, is definitely appreciated.

Originally Posted by Bry
On the replacement set I hand reamed out the screw holes ...
Sounds like a good way to deal with this. I'll park it in the back of my mind for later when it's time to take care of the badges. For the time being, though, the Spitfire has turned into an obstacle for me to step around…

The Spitfire is on a temporary hold while I work to determine specifically what "consumables" I need for another bike (valve guides, bushings, bearings, …) so I can get them ordered. This then resulted in me spending over a full day welding up a piece missing from a broken steel casting then machining the filler back in shape to be ready for a chunk of chrome-moly that I ordered to finish the repair. That reconstruction work then came to a halt for a couple of days while waiting for the steel to arrive, which it did today (I have plenty of steel to work with; unfortunately, much of what is labeled is unweldable free machining steel, and I didn't want to risk this repair on some unlabeled, unknown alloy). Anyway, as long as I can keep things straight, working in parallel lets me move from task to task (and bike to bike) instead of coming to a full halt every time I have to wait for something.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/10/14 4:07 pm

Well, only four more things to do and my Spitfire will be done: i.e., front end, rear end, engine, and gearbox… Oh, and painting the frame, oil tank and fuel tank.

Thus far my effort to restore two bikes in parallel is working well, but twice as many bikes means progress on each is half as fast. But, I have moved forward a little on the Spitfire, with the gearbox the next item I will be dealing with.

The next photograph shows the SCT2 gearbox mounted in a stand I made for pre-unit BSA gearboxes some time ago. The height of the supports is such that the gearbox can rotate a full 90-deg. CW and CCW, and the separation is that of the upper, wider, gearbox lugs (you can see the spacer for mounting on the narrower, lower lugs), so I can position it anywhere within the full 360-deg. when working on it.

[Linked Image]

The reason for the stand isn't just to hold the gearbox when on the workbench, but to hold it rigidly to make it easier for precision measurements (e.g. of bushing IDs, separation between components, etc.). The indicator shows how such a measurement would be done on the shaft for the clutch arm, although in this case the amount of play in it is over 1/16" so it hardly requires an indicator to know there's an issue to be dealt with. Since this cover isn't unique to a Spitfire's gearbox I'll probably take the easy way out and swap one from another gearbox. However, machining a bushing and/or welding and re-machining the hole also are options. Closer inspection of this photograph shows a socket head cap screw at the upper right of the inspection plate. If it turns out the case has been tapped for a U.S. thread some work with TIG and a helicoil will be needed here, so it's unlikely restoring this gearbox will be a simple matter of just substituting fresh components.

The next photograph shows a gearbox housing that I modified several years ago by machining away every surface that I possibly could (I bought a broken housing on eBay so no useful parts were injured in making this picture). This lets me observe in detail the operation of a complete gear cluster to make sure there are no issues, and to determine the size and location of shims to improve the operation.

[Linked Image]

I already have the replacement needle bearings for this SCT2 so unless disaster awaits me inside the case I expect the major amount of time needed to restore this gearbox will be for cleaning the oxidation from the casting with a mild grade of Scotchbrite and in polishing the outer cover.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/17/14 2:05 pm

As of a week or so ago my plan was to work on the gearbox next. But, plans can change, and this past weekend I took the head off my Spitfire for the first time since buying it 20 years ago. As I mentioned earlier in this thread, for a long time I had intended to use the 67-1106 dual carburetor head I found for it back in the 1990s. Because of this I wasn't too concerned with whatever head was currently attached to the engine. Still, it's not that I hadn't tried to read the casting number on the underside of the inlet manifold using mirrors and a borescope, but I could only barely make out two of the six numbers. To have any hope of doing better would require removing the head so I could examine the casting more closely.

Heads and Valves

Before showing what I found, I'll digress to discuss what I was looking for. The Alzina parts list shown much earlier in this thread gives 67-1127 as the part number for the head. Interestingly, it gives 67-968 for an "inlet valve" as well as 67-961 for an "oversize inlet valve." Nothing else on this parts list is for optional or performance tuning equipment so this dual listing begs the question of whether Spitfires with two types of heads were shipped by the factory in 1957, one with the early Super Rocket valves (67-968) and one with later "Big Valve" Super Rocket valves (67-961). The 67-967 exhaust valve on the list is the same as in both Super Rockets.

Although BSA introduced the Super Rocket to the U.S. in 1957, the earliest Spares book I own where it shows up is 1958. However, this 1958 book shows the Super Rocket as having the smaller 67-968 valve. The first time the term "Big Valve" occurs is for the 1959 model year where BSA literature says it has a new engine now with "bigger intake valves" among other improvements.

I haven't yet confirmed all the information myself using BSA literature, but Dave Comeau's website also has relevant material on heads and valves:

http://atlanticgreen.com/a10alloyhead.htm

There he identifies 67-961 as the 1.5" intake valve that was used starting with the 1959 "Big Valve" Super Rocket and later on the Rocket Gold Star and Rocket Gold Star Spitfire Scrambler. So, might this mean the 1957 Spitfire represents another first for BSA, i.e. a "Big Valve" head two years earlier than is currently believed this feature was introduced? With questions like that in the background, off with my head…

The Head on this Engine

I didn't take photographs while removing the head because there is nothing unusual about doing so. Just the usual hidden bolts to find and inaccessible fasteners to reach, typically located directly over bottomless pits, that always make life interesting for the rebuilder.

The inlet port looks to be unaltered and is a quite uniform 1.143 - 1.146" diameter. This is only ~0.08" larger than the 1-1/16" carburetor supplied on this machine, i.e. consistent with it being a "modified [Rocket] alloy head to accommodate a 1-1/16" Monobloc carburetor".

[Linked Image]

[to be continued]
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/19/14 10:03 pm

Although the photograph in the previous post showed that the inlet tract was unmolested, it certainly doesn't mean the head hadn't been used. As can be seen in the next photograph, removing it from the engine revealed that it's at least few miles overdue for a decoke:

[Linked Image]

The pistons are just as bad:

[Linked Image]

[Linked Image]

I haven't taken the valves out of the head yet so at this point I don't know if they are original valves, or if they might have been installed later, but the inlet valves are ~1.5" dia. and the exhaust ~1.4". Both of these sizes are of valves on the Alzina parts list, as well as on "Big Valve" heads currently believed to have first appeared on the 1959 Super Rocket. I'm not sure if I will be able to tell after disassembling the head whether the valve seats are as they left the factory or if they were later enlarged by a tuner in order to install the 1.5" inlet valves.

Having removed the head I can now see that the casting number is barely there. The individual numbers haven't been ground off, they were just poorly cast. Of the three numbers that are somewhat visible, one is so feint that I can only barely make it out with grazing illumination using ultraviolet light (hey, I have the technology, so might as well put it to good use, right?). As an aside, the UV causes the oil to fluoresce rather brightly, as can be seen in the next photograph.

[Linked Image]

This photograph indicates why UV can be a big help if you have a small crack or oil leak that you having a difficult time pinpointing. But, I digress…

Back to the casting numbers on the inlet manifold. None of the photographs I took does a very good job revealing them, but the following is as good as any:

[Linked Image]

From close study under magnification and using visible, UV, and IR light at various angles I can tell that the casting number ends with 125 or 126, or less likely 128, but I can't discern any digits before these three. It might seem required that the last number in the sequence be an 8 in order for this to be the proper 67-1127 head since BSA typically assigned part numbers one digit smaller than the casting numbers. However, the small number of Spitfires made and the way the model was rushed into production more than four months into the year makes it unlikely a special casting would have been produced just it.

More likely is that Spitfire heads started life as standard ones for Super Rockets and that subsequent machining operations modified them into Spitfire form. The part number for the 1958 Super Rocket head is 67-1125, and it seems likely the same head was used when the model made its debut in 1957. In this case the usual BSA practice would have the casting number for it as 67-1126. With this in mind, look again at the above photograph. Not only does the casting number appear to end with "26," there is a "-S" stamped into the head immediately after the number. This marking takes on added significance since it is consistent with it denoting a Spitfire modification to a Super Rocket casting.

While on the subject of stamps, in the hopes someone knows what it means, on the far right side of the inlet is "CG 82":

[Linked Image]

My conclusion from the above evidence is that the head that came with this machine when I bought it 20 years ago is indeed a genuine head for a 1957 Spitfire. It also means that in addition to the engine cases, gearbox, frame and carburetor we now add head with "67-1126 -S" to the list of components with markings unique to the 1957 Spitfire.

The World's First BSA "Big Valve" Engine?

BSA advertising material says the Spitfire has a "Rocket type" engine, "although it differs in several respects from the road type Rocket engine." Differences given are that it has "enlarged inlet ports," an "enlarged intake port for better breathing," as well as a "modified alloy cylinder head" to make use of the 1-1/16" Monobloc. The wording implies it has both larger inlet ports, i.e. at the valves, as well as a larger intake port, i.e. at the carburetor. Again, on the Alzina parts list for the Spitfire is an "oversize inlet valve," 67-961, which is the part number for the 1.5"-dia. component from which the "Big Valve" Super Rocket engine got its name two years later. So, in addition to this Spitfire being the world's first "Rocket Gold Star" (albeit, with a different name), does this also indicate it houses the world's first "Big Valve" A10 engine?
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 01/20/14 11:05 am

Interesting, to say the least...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/24/14 2:12 pm

Continuing on with further details of the Spitfire's engine:

The Cylinder Barrels

The cylinder barrels of 1956 and 1957 Road Rockets as well as 1958 and later Super Rockets were "thick flange," part number 67-1210, which alone makes it virtually certain the 1957 Spitfire used these as well. Although the casting number on my Spitfire's cylinder barrels is not very crisp, comparing it at the top of the following composite with one from a 1962 Super Rocket at the bottom shows with high certainty that the blurred number of the Spitfire is the expected 67-1210. Earlier "thin flange" cylinders werecast with right side-up 67-1074 and neither the thickness of the flange, nor the orientation of the numbers, nor several of the numbers themselves, are consistent with this. In this case the casting number is the same as the part number, whereas usual BSA practice would have it 1 digit higher, showing that BSA wasn't always consistent.

[Linked Image]

With my bore micrometer set to the nominal 70 mm (2.7559") bore of an A10 engine I found the cylinders are ~0.0025" larger than this a few inches below the top of the cylinder (2.1 thou. for the right and 2.5 thou. for the left), but worn to ~0.008" larger just below the top (8.5 thou. left; 8.1 thou. right). So, these cylinders have never been bored, although they will have to be now if they are to be used in this restoration.

This raises an interesting question in the context of this particular restoration: which would be more "authentic," boring these cylinders and using NOS +020 pistons of the same manufacture as the ones currently in it, or reusing the current pistons (assuming they aren't worn) along with a replacement set of barrels that don't need to be bored?

The Pistons

Despite how dirty the tops of the pistons looked in the previous post they turned out to be pretty easy to clean. The plastic tip of the shop vacuum knocked off most of the big chunks (and also carried them away), and 15 sec. with a brass brush on an air grinder took care of the rest. This revealed the BSA number 67-1371 (i.e. part number 67-1370) stamped into them:

[Linked Image]

The 1958 BSA Spares manual shows these 67-1371 pistons are the 8.26:1 ones used in Super Rockets that year (surely, this is a typo and should be 8.25). So, are these the original pistons for this 1957 engine? BSA literature on the compression ratio of the Spitfire's engine tells a slightly mixed story. Although early magazine articles based on a BSA press release said they would be 9:1, a 27 March 1957 Alzina release says 8:1 and an undated East Coast release has '8' typed over the '9'.

Unfortunately, BSA Spares manuals are oblivious not only to the 1957 Spitfire, they're also oblivious to the fact the Super Rocket appeared in 1957 as export-only. The manual shows in 1957 there were 8, 8.5, and 9:1 pistons for the A10 and Road Rocket, and in 1958 7.25 and 8.26:1 for the Super Rocket. If this engine had been rebuilt many years ago but had not been bored, it is still possible different pistons could have been substituted for the originals at that time. Similarly, if the barrels had been damaged and required replacing, it is possible new ones along with new pistons were installed. However, neither of these scenarios is probable.

In any case, although I can't be completely sure, based on all the information I've found on the Spitfire's engine, the use of these Super Rocket pistons is consistent with them being original to the engine. Absent any information to the contrary coming to light, I intend to proceed accordingly.

Speculation -- Were Spitfires Produced With Two Different Heads?

In the previous two posts I noted that the Alzina parts list has two types of inlet valves on it, one an "oversize inlet valve." This leads me to wonder if Spitfires actually might have been shipped in two versions, one of which had a "Big Valve" head. Here I'll speculate on why this might be the case, and on how people who own 1957 Spitfires can help resolve this issue.

As discussed much earlier in this thread the Spitfire was a last minute addition to the 1957 model range. It appears that Hap Alzina had a hand in determining its configuration, and shipments to the east coast didn't start until a month after batches had been sent to the west. An early Alzina press release notes that only "high rev" valve springs and keepers would be needed to make it perfect for drag racing. What is needed for both drag racing and high speed Barstow-to-Vegas scrambles that were characteristic of competition in the West is an engine that produces the highest possible h.p., i.e. one with a head that flows as much air as possible. For this purpose a "Big Valve" head is ideal.

While a bigger port flows more air it does so at lower velocity. Unfortunately, the lower velocity provides less of a signal to the carburetor at lower rpm which makes the engine less flexible. This is less than ideal for many types of off-road competition, especially on a machine with only four speeds. So, given the presence of two types of inlet valves on the parts list, my speculation is that sometime after the initial shipments a number of the later 1957 Spitfires might have come from the factory with heads having the smaller valves. Although I probably can't convince many owners to remove their heads to check this, perhaps I can convince a few of you to take a flashlight and mirror out to the garage and look at the casting number. Does it have an "-S" stamped after it? Does it have some other letter or number stamped after it? I'm sure everyone following this thread this eagerly awaits the results of what you find.

The casting number is on the underside of the inlet runner that goes to the left cylinder, i.e. on the primary side of the engine. The next photograph shows the number on my Spitfire's head as well as on a head that recently sold on eBay for $510 with ten people bidding on it:

[Linked Image]

The Next Steps

This weekend I'll put the head on the barbeque to boil for an hour in a pot of water with Dawn detergent. After that I'll remove the valves to look for any numbers that might be stamped on them and closely inspect the inlet valve seats to try to determine if they originally came from the factory as 1.5". At that point it should be about time to fire up the TIG welder to reconstruct the broken and missing fins.

[Linked Image]
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/24/14 5:15 pm

if any one knows about these numbers the ones on my 57 spitfire are CG57 with 58A27FX underneath on the cyclinder head and 67-1210.
have you got a date when you think this will be finished magnetoman
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/24/14 10:54 pm

Originally Posted by paul67
CG57 with 58A27FX underneath on the cyclinder head
Can you identify the location of the 58A27FX better? Are you saying you found this on the underside of the left inlet runner of your head, where 67-1126-S is on the two heads shown at the bottom of my previous post?

As for the meaning of the CG82 stamped on my head, and the CG57 on yours, I'll go way out on a limb. Ignoring the CG, if 82 means the 8th day of February, that was a Friday in 1957, i.e. a work day. My bike was dispatched five days later, so the timing works for this to be a date code. Your bike is CG 57, which would be July 5 if this is what the code means. That also was a Friday. I think you sent me your engine number in the past but I would have deleted the email exchange. If I did give you the dispatch date of your engine, was it after July 5?

Even before getting your answer, and going further out on that limb, assigning numbers to the CG they would be 37. Using only a single digit code for the year wouldn't be unprecedented ("hey, we'll deal with 1967 when it happens"), leaving only the 3 as a mystery.

Originally Posted by paul67
have you got a date when you think this will be finished
My current plan is to finish this restoration before hell freezes over, but that schedule may be too optimistic so please don't hold me to it…

Seriously, after it sitting for 20 years while I did nothing but collect the missing parts (which, if you look at the first post in this thread, counts as doing more than nothing), I decided to force myself to get started on this restoration despite having too many other commitments. It's slow going since it only moves forward when I'm able to steal bits and pieces of time from other activities, but I'm forging relentlessly ahead. Realistically (if I can even pretend to apply that word to this endeavor), I will be very happy if it is finished by the end of 2014, although I am hoping it will be sooner.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/25/14 10:58 am

Aug 28 was the date you gave
the numbers are on left side by the inlet manifold
[Linked Image]
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/25/14 11:23 pm

Originally Posted by paul67
Aug 28 was the date you gave
the numbers are on left side by the inlet manifold
This is very interesting. Although we only have the two data points thus far, they're consistent with the numbers being the month and day the head was stamped after making the "-S" Spitfire modifications. As I wrote in my earlier post, mine is stamped on the right side (and without those other numbers/letters).

It even makes sense that at the start of production in February the heads were modified only shortly before the bikes were assembled and shipped, but by summer the total number of machines that eventually would be produced was known so the necessary heads could have been modified further in advance than a few days.

When you're feeling limber, please crawl around on the garage floor with a flashlight and mirror to look for the casting number on the bottom of the left inlet manifold. And, anyone else with a '57 Spitfire -- and I know there are at least a few of you who are reading this -- please do the same.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/26/14 5:38 am

the engine is on the bench, i will start dismantling it in the next few days so i will get a photo of it
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/26/14 8:40 am

[Linked Image]
67-1126 with a -S after
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/26/14 10:19 pm

Originally Posted by paul67
67-1126 with a -S after
Excellent. Thanks very much for doing this. We're doing a better job nailing down the mysteries of this low-production '57 BSA than the "dash Y" guys are doing on much more common bikes of a decade later... (just kidding, guys).

I have the valves out of my head now and as far as I can tell the inlet valve seats are the stock ones. Since the OD of these valves is 1.54" this certainly seems to indicate it is the very first "Big Valve" head produced by the BSA factory. If further measurements confirm this, it's something new for the history books. I'll have more to say about the head and valves when I have time to write up this weekend's work.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/29/14 4:02 pm

i was just looking at your pistons, the one's in mine are high compression with the domed head. May be some low compression one's would make it easier to kick over
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/29/14 11:38 pm

Originally Posted by paul67
the one's in mine are high compression with the domed head. May be some low compression one's would make it easier to kick over
I'm limited by my self-imposed constraint of originality to use whatever pistons came with the engine when new. However, even if I weren't, it seems to me that ~8:1 is perhaps the best compromise for a non-racing bike between h.p. and flexibility with current and future fuels. And easier to kick over as well.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/02/14 2:25 pm

"Big Valve" Head (continued)

Continuing on the subject of "big valves," the next photograph shows that both the intake and exhaust valve seats are largely unworn. Dirty and rusty, yes, but unworn.

[Linked Image]

The OD of the intake valves are 1.54", and the ID and OD of the seats are 1.41" and 1.54". This ~0.013" width of the intake seats is the same as that of the exhaust seats (1.28" ID; 1.41" OD; 0.013" width -- exhaust valves are 1.39" OD). The only other A10 head I have to compare it with is my dual-carb one, and the valves in that one were ground pretty far into the seats so I can't estimate their original widths. However, from the fact the inlet valve seats and bowls on the Spitfire head appear to be just as they came from the factory this means that as far as I can tell it is the world's very first BSA factory "Big Valve" head.

There are no marks on the stems of the exhaust valves (I haven't cleaned the faces yet), but the stems of the intake valves have XX3263KES on them. Is this anything anyone reading this is familiar with?

Cleaning the Head -- Solvents

I next boiled the head for 4 hours in Dawn detergent on the barbeque and then let it soak overnight as it cooled off. This left the head quite clean. However, it also revealed that much of the head had been painted black at some point in its life, and that there was a lot of paint residue between the fins.

I then bought a disposable Al baking pan, lined it with foil (so I could reuse the pan, if needed), and then soaked the head for an hour in a witch's brew of MEK and trichloethylene. Note, these particular chemicals are very hazardous to your health, so do not do this yourself without adequate precautions. The solvents removed additional oil from the head which can be seen in the bottom of the pan (long with paint residue) after the solvents had evaporated.

[Linked Image]

The head has led a hard life so there are a number of nicks to smooth out and/or fill in with TIG.

[Linked Image]

Cleaning the Head -- Soda Blasting

Unfortunately, paint was still stuck in many nooks and crannies after the above solvent cleaning processes. I decided to try soda blasting (after first testing it on other Al to make sure it truly does not etch the surface). Although soda blasting does not get universally positive reviews, it seems most of the negative comments come from people who mistakenly used it to try to remove rust from steel. If it didn't do what I needed I would have to find some other way to remove the paint residue before I could weld the cracked and missing fins because otherwise there would be too much contamination near where I needed to weld.

I bought a Harbor Freight soda blasting outfit and 50# bag of soda. For those of you not in the U.S., Harbor Freight sells poor quality Chinese-made tools at very low prices, with frequent sales as well as weekly 25% off coupons in the paper to make them cheaper still. Although you definitely get what you pay for at Harbor Freight, their low tech items that are mostly just chunks of steel (e.g. engine stands, hydraulic presses, etc.) certainly are reasonable. Anyway, a sale tempted me into buying one of their soda blaster sets with this head in mind.

Although I've had this soda blaster for several months I hadn't tried it until now and, while in operation it lived down to my expectations, the soda did a very good job removing everything that needed to be removed. That said, like any blasting job, it always takes me several rounds of blasting, inspection, and re-blasting to get everything off so cleaning of the head isn't finished yet. However, the paint is gone from everywhere I need it to be gone from for welding so the head moved on to my welding table.

Restoring Fins by TIG Welding

Below are before and after photographs of the one small fin I built up so far using 1/16" 4043 TIG filler rod (the black on the top fin of the 'after' photograph is the reflection of an unlit section of the garage ceiling).

[Linked Image]

After building up sufficient material I spent another half-hour or so (I didn't keep track of the time) with files and carbide burrs and abrasive pads in die grinders getting the fin close to the proper shape, although it still needs some more tweaking before it will be finished. Unfortunately, detailed restoration work like this is very time consuming so by the time I'm done with everything I'll easily have $5k worth of my time in this head. Clearly, not many people (myself included) would be willing to pay what it costs to have work of this type done.

Returning this head to its former glory isn't going to be a quick job. Over the next weeks there will be more welding, grinding, blasting, and welding some more to deal with the defects one at a time.
Posted By: Rickman

Re: 1957 BSA Spitfire Scrambler - 02/02/14 2:43 pm

> intake valves have XX3263KES on them

MM,
The only thing I can say toward this, maybe, is WAY back in the later '80's, when you could go down to Domi-Racer and sometimes get to forage through the back room shelves on your own, when they were too busy, or they couldn't find what you were searching for....

In a box with only a few odd items in it, was a large stem valve, of some large size.
I was looking for something like this for my AJS that had its intake enlarged by quite a bit....

The valve dropped in and FIT! Marvelous!

All I can remember for certain, there were FOUR [4] X's in front of the number on the valve stem.
Near as I can guess? And it IS a guess....

The valve was 4 sizes larger than the stock size?
Because, a stock intake valve went right past the valve seat in this head, without ever touching the seat, or in the seat's area.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/02/14 4:44 pm

Originally Posted by Rickman
All I can remember for certain, there were FOUR [4] X's in front of the number on the valve stem.
Near as I can guess? And it IS a guess....
Hmm, that is interesting. Thanks, it might help me as I try to track down more information on this. I haven't had it confirmed yet, but I've been told that BSA 1.5" valves actually were 1.5", whereas mine are a little larger than that. Possibly not XXXX larger, but maybe XX larger?...

Again, thanks very much for this information.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/06/14 4:38 pm

TIG Welding of Fins

Offline a couple of people asked for more details about how I TIG weld fins. There is no way a post even much longer than this one could teach anyone to weld, but I hope some readers find the following useful despite this.

For some reason TIG has a reputation as being limited to specialists, but I found the skills from the gas brazing and welding I had done for years to be directly transferrable. If you are familiar with gas welding, think of TIG as having the pinpoint control of a #000 tip with the heat output of a #4. At the same time the area of the weld is bathed with an inert gas (usually argon) which is what allows aluminum to be welded.

I learned on a 450 Amp transformer machine, but the inverters that started taking over ~15 years ago are easier to use and more flexible, allowing each amp to be more effective. The machine I'm using for the Spitfire's head is a 200 Amp inverter with a water cooled torch. Although I had it set at 140 Amps for the fin I reconstructed in the above post, I never had the foot pedal fully depressed so I probably was using under half the capacity of the machine. I have yet to run into any welding problem on a motorcycle where I needed more power than this Miller Dynasty 200DX provides, although that doesn't mean I might wish I had more sometime in the future (but, I do have full access to that 450 Amp machine). Also, since work of this kind requires more precision than, say, welding a trailer hitch, I use a "cheater" lens in my helmet to magnify what I'm welding.

Choice of Filler Rod

Although 4043 is the filler rod most often recommended for various wrought and cast alloys I first wanted to find if something else might be better. So this past fall I experimented with 4043 and two other fillers (4047 and 4145) using broken BSA heads and cases sent to me by several people on BritBike (thanks again, guys!). However, 4043 worked as well as any of the others on BSA's casting alloy so it is what I have been using on this head.

I prefer smaller diameter filler rather than larger since it provides me with more flexibility in the build up process. Even where the fins were ~1/8" thick I used 1/16" diameter filler. The next photograph is the one I used in a post a few days ago, showing a fin that I built up 1/16"-dia. 4043 welding rod.

[Linked Image]

Color is another important factor, since even though various Al alloys only have very slight differences in hue it can be especially noticeable on large surfaces (e.g. the side of an Al fuel tank). However, the color match of 4043 to the alloy used for the head is very good.

Restoring Missing Fins

For a fin like the one shown above think of the welding process as something like building up material row-by-row using a silicone sealant that dries almost instantly after being squeezed from the tube. One row is deposited, then the next on top of it, etc. until more aluminum has been laid down than constitutes the final fin. The next step will be to grind away the excess so if I later find I missed a place I have to fire up the torch again to fill it in. Although this is usually no problem (although it can be), at a minimum it means additional time to clean up the grinding and get everything set up again for more welding.

Careful welding to avoid voids is important for work like this, not for strength or to avoid oil leaks, but for cosmetics. Voids will show up as pinpoint (or larger) holes in the surface after the fin has been shaped. If that happens your only choices will be either to live with it, or grind them out, fill them in with more welding, and do the work to reshape the fin all over again.

Although the fin shown above is a small one, to construct larger fins I fashion appropriate piece of ~1/8" copper to serve as supports to minimize the build-up of excess weld material below the final shape of the new fin. Because of the tight spacing between fins removing the excess below a fin is difficult so it helps to have as little as possible to deal with. Copper works for this because the Al weld doesn't stick to it.

Reattaching Broken Fins

I use pieces of Cu as spacers when reattaching fins as well as when constructing them from scratch. I file and shape the Cu until it gives the correct spacing between the broken piece and fin below it. Although fins might look like parallel planes, closer inspection shows a variety of tapers and ridges to deal with when shaping the Cu. After grooving the edges of the broken piece of fin and the mating piece on the head, I clamp the piece into position using the Cu spacer(s). I then tack the fin at both ends and, before finishing the weld, carefully inspect to make sure the spacing between fins is correct, the broken piece isn't slightly above or below the correct surface, and that it isn't tilted in any direction.

Since the fins are regularly spaced, any defect in the orientation of the reattached piece will stand out. Having said that, the tip of the fin in the photograph below is slightly closer to the fin below it than it "should" be. However, the reason is the fin itself droops at the end, which appears to be how it was cast. Since the alloy used for the casting is fairly brittle, any attempt to remove the droop very likely would cause it to snap. This illustrates that even if the best tools are available, in the end reconstructing fins relies to a great degree on subjective judgment.

[Linked Image]

Grinding, Milling, Filing, and Shaping

After doing the welding, the fin still needs to be shaped. I use a set of carbide burrs made with widely spaced teeth that keep them from loading up. Although in a 20,000 rpm die grinder they remove material really fast, that also has a downside. The teeth can gain traction without warning and in a heartbeat be grinding a few inches away where you don't want anything ground away. Also, even small carbide burrs don't fit into all the spaces where metal needs to be removed. So, for removing excess weld material I normally install the head in a vise for my mill that tilts as well as swivels on two axes since the mill allows me to remove the bulk of the material from tight spaces with less chance of mistake than with carbide burrs alone. Depending on how much working room there is (and there isn't much on "internal" fins like the one shown earlier in this post), this vise in combination with 45-deg. and 60-deg. dovetail cutters, Woodruff cutters, slitting saws, and/or standard end mills lets me reach above and below the fin to remove excess material. Some manual filing almost always is required after the milling, as is sometimes the use of small carbide burrs in a pencil-size die grinder. Assuming there is enough access to the area of the repair, I do the final shaping with several grades of Scotchbrite pads in die grinders.

Texturing

Unfortunately, someone polished the top fins of this head at some point in its life so eventually I will have to deal with the issue of the original sand cast texture. On the bright side, it makes blending the TIG welds a lot easier since the adjacent surfaces are smooth so I don't have to worry about keeping the blended area as small as possible.

As can be seen from the above description, reconstructing fins is time consuming. However, even for fairly common BSA, Matchless, Triumph, etc. heads doing so is the difference between reviving a piece of metal that otherwise is scrap, or needing a replacement that could cost upwards of $500.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 02/07/14 10:27 am

That's a good, detailed write-up, Magnetoman. It should prove helpful to many in the future, assuming they have your skill, patience, and perseverance. It is amazing how much time and effort it takes to reverse what someone else did in one careless instant sometime long ago.

I am curious as to where you used your HF soda blaster. Did you use it inside a cabinet, or perhaps outdoors where the wind could carry away the snowy powder? I have blasted with soda inside a cabinet in the past. It worked O.K., but I later found that I was doing it wrong. I was letting the soda drop into the hopper, where it was mixed with the fresh soda and being re-used. I now understand that the soda is a single-use material. It fractures to powder as it hits the surface. I guess it can be used in a cabinet, but with a feed from a separate hopper. What falls inside the cabinet should then be thrown away. I would like to know what worked well for you?

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/07/14 3:31 pm

Originally Posted by TR6Ray
It is amazing how much time and effort it takes to reverse what someone else did in one careless instant sometime long ago.
Boy, isn't that the truth.

Originally Posted by TR6Ray
I am curious as to where you used your HF soda blaster. Did you use it inside a cabinet, or perhaps outdoors where the wind could carry away the snowy powder?
I used it outside on a breezy day when it was supposed to rain in the afternoon, which would have washed away the evidence before my wife got home. It didn't rain so the driveway is still a grayish-white. Also, the breeze was of no help because half the time the shape of the head sent the soda straight back into my face. A face shield and mask are necessities.

Before all the bad things I'm about to say about the HF soda blaster, it worked as well as I expected so I am not sorry I bought it. That said:

-- it's a real pain to fill. It has a small opening so even with the largest funnel that fits it takes forever to fill. Although mine is their 15 lb. unit, I lost patience when it was less than 1/3 full and used it at that point.

-- however, had it been completely full it would have been even more difficult to use. I had to hold it in my left hand and keep agitating it in order to keep the soda flowing. Trying to aim a nozzle with my right hand while shaking a heavy weight in my left has its limitations. Another 10 lbs. of soda in it would have made it much more difficult and frustrating to use.

-- it only has an on/off valve, located on the tank itself, so basically it's on all the time. Setting the bottle down and switching off the toggle valve took enough time that most times I just aimed the nozzle off into space while repositioning the head. With a blasting cabinet you can stop the flow with a foot pedal or trigger, wait a few sec. for the fog to clear, see the spots you missed, and continue on to get them. It isn't practical to do this with the HF unit.

-- the hose is too stiff

The whole point of using soda is so it won't etch the surface, so switching back and forth between it and an aggressive media in a cabinet wouldn't be ideal because of the difficulty of getting all the previous media out. And that's ignoring the issue you mentioned of not wanting to recycle the soda, which every cabinet I can think of is designed to do. So, it would require its own dedicated cabinet, which takes up space. Which means, unless I find myself needing to soda blast more than ~2 items per year I'm afraid I'm going to have to live with all the limitations of this HF unit. However, if I can find a "deadman valve" cheap enough, that addition alone would significantly improve this blaster.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 02/08/14 1:14 am

Originally Posted by Magnetoman
The whole point of using soda is so it won't etch the surface, so switching back and forth between it and an aggressive media in a cabinet wouldn't be ideal because of the difficulty of getting all the previous media out. And that's ignoring the issue you mentioned of not wanting to recycle the soda, which every cabinet I can think of is designed to do. So, it would require its own dedicated cabinet, which takes up space. Which means, unless I find myself needing to soda blast more than ~2 items per year I'm afraid I'm going to have to live with all the limitations of this HF unit. However, if I can find a "deadman valve" cheap enough, that addition alone would significantly improve this blaster.

This company TPTools & Equipment sells higher end blast cabinets, although they also sell parts and plans for building your own setup. Anyway, their idea is to sell you an external hopper for soda. When you want to soda blast, you empty the normal blast media from your cabinet (glass bead or whatever) and leave the cabinet empty. Then you siphon soda from an attached hopper, but use your normal blast gun inside your cabinet as usual. The spent soda falls to the bottom of your cabinet and stays there. When finished, you empty the used soda from the cabinet funnel and dispose of it, then pour your normal blast media back in and you are set.

Drawing soda from an external source prevents accidentally getting leftover aggressive media mixed in, and the soda is contained in the cabinet. This would work, but would be a lot of fooling around. As you said, if I were doing more of this, I would have a dedicated cabinet for it. I just don't have the space. The one cabinet I have now is really in the way. The soda surely does have its advantages though. It makes gasket removal from machined alloy surfaces very easy.

Thanks for the honest testimonial. I was wondering how one of those units would work.
Posted By: BritTwit

Re: 1957 BSA Spitfire Scrambler - 02/08/14 9:18 am

Last year I sent my engine castings to a local metal finishing company for soda blasting. $175 bill and received a clean but splotchy finish (pieces were pre-cleaned my me). He said he used a cabinet and dry media method. I then did them again with another set of cases. I used my commercial grade Hotsy pressure washer with a siphon attachment. Using a 5gal pail and keeping it at least 2/3 full with commercial grade blasting soda, I got a more uniform and brighter finish. The water prevented the dusting associated with a dry blast cabinet. I don't know why, but a higher pressure wet delivery seems to deliver better results.
The commercial grade soda that I used was coarser and left behind a grainy residue. I took a bit of this residue in my palm and added water and was able to break it down (note - left my palm very clean, like Boraxo). So with this in mind, a final plain high pressure rinse would be in order.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/08/14 11:19 pm

Originally Posted by TR6Ray
… an external hopper for soda. When you want to soda blast, you empty the normal blast media from your cabinet (glass bead or whatever) and leave the cabinet empty … This would work, but would be a lot of fooling around. ... I just don't have the space. The one cabinet I have now is really in the way.
Yes, the space issue is the real problem for me as well. Even better than 2 dedicated cabinets (glass beads and soda) would be a 3rd (walnut shells). But most of the time even a single one just sits unused taking up a lot of space.

Originally Posted by TR6Ray
I was wondering how one of those units would work.
I used my HF soda blaster again today and my impression of it is better than after the first use. It's still HF "quality," but it actually does the job reasonably well once I learned to live with its "features."

This time I had the unit sitting on the ground next to my left leg where I could easily jostle it using the stiff hose to get soda flowing again whenever it stopped. Also, thanks to having had more time with it I could easily find the on/off valve with my left hand without looking so it was only a little less convenient than having an actual foot pedal to control the flow. This let me stop the flow, inspect to see what areas needed more work, and start up again a number of times. It's still a pain to fill, but for use only a few times a year that's totally acceptable.

It was a calm day today and when I was done I was able to sweep up all the soda from the wide area behind the garage where I did the blasting. However, only half the soda I used was in the pile I swept up so where the rest went is a mystery (not past the mask into my lungs, I hope).

After two sessions totaling no more than a half hour (I didn't time it) the head is now clean of all paint, gaskets, carbon, etc. and the Al is much brighter than when I started. I estimate I used about 10 lbs. of soda for this job, which means the cost of materials was less than $10 (ignoring the cost of the unit itself). There is still some staining at the base of a couple of fins on one side that the soda just won't deal with, and it is not yet "show quality" at this point, but I can't imagine how I could have cleaned this head without the soda blaster. I still will spend a number of hours with Scotchbrite pads and gentle polishing compound(s) before it will be done, but I won't get to that for a while. There are still two more fins to be welded.

Originally Posted by BritTwit
I don't know why, but a higher pressure wet delivery seems to deliver better results… a final plain high pressure rinse would be in order.
If I had a high pressure washer easily available I definitely would have tried this.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/19/14 1:49 am

Note: I just discovered 80% of the the post I uploaded two days ago disappeared, so there's something funny going on with this site. I deleted the remnants and have uploaded it again below:

Despite a delayed and rerouted trip to the snow-covered east coast I made some progress this week. Today I was able to build up the most difficult of the broken fins, although shaping it is on hold until a large diameter slitting saw arrives. The next photograph shows the setup I used for the welding.

[Linked Image]

The photograph doesn't do a good job of showing the three dimensional shape of the fins. Starting from the bottom there's a 1/8" Cu plate in the shape of the missing fin, pressed against the lower surface of the fin by a folded brass shim stock "spring." Since the Al weld doesn't stick to Cu this serves as a "mould" to minimize the need for subsequent shaping of the fin.

Next is a ~1/8" OD Cu tube whose end is crimped and into which I've drilled four holes through which I flowed Ar while doing the welding. At the right is an Al foil "dam." A matching one was at the left for the welding but I don't have it in place here to allow a better view. While welding I had the head tilted up by ~30-deg. (from back-to-front in this photograph), which trapped the Ar in the cavity formed by the fins and dams. Above the Cu tube is the second broken fin, with a pointed protrusion that extends out quite far. This protrusion is what made it difficult to weld the central section of the fin below.

In principle I didn't even need a cup for the TIG torch since the entire region of the weld was bathed in Ar. The reason for doing this is I had to extend the TIG electrode by ~3/4" to reach the deepest region beneath the pointed protrusion of the broken fin above. In the best of circumstances 3/4" stretches the limits of a gas lens to provide shielding coverage. Although I don't know for sure if I needed to make the well for the Ar, should this deepest part of the weld have been bad it would have been difficult to grind it out without risking damage to the fins above and below it. Anyway, once I had built up the central section somewhat the dams and tube were no longer needed.

Welding of this fin went off without a hitch. Thanks to the Cu the bottom of the new fin is flat and slightly tapered, as it should be. Shaping the top of the fin awaits the arrival of a larger dia. slitting saw than any of the ones I already have. Once that is done rebuilding the fin above it should be much easier than this one.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/23/14 10:25 pm

While waiting for the larger diameter cutter to arrive I decided to get started using one of the largest slitting saws I have. The next photo shows the Spitfire's head mounted on my mill in a Brown & Sharpe vise that tilts and rotates in three axes to within a few tenths of a degree. This allows alignment of any surface of the head precisely parallel to whatever cutting tool I am using.

[Linked Image]

Two 3/8" bolts attach the head to a 5" long 2"x2" bar of Al which itself is clamped in the vise. Although this setup is quite rigid for present purposes, the fins are largely unsupported so they can ring with certain cutting tools and rpms. Although it wasn't necessary with the fin shown above, with an earlier one I used two rubber grommets compressed between the fins to eliminate the ringing.

As can be seen in the above photograph the material that had been missing from the fin is now completely filled in. At this point the slitting saw already has removed quite a bit of the excess material from the top of this "new" fin, although more needs to be removed from deeper between the fins than this saw could reach. While it appears that the freshly-machined Al nearest the exhaust port is darker than the rest, this is an artifact of the lighting.

It also can be seen that the material for the "new" fin extends out too far (it's only ~1/8" too far although it looks like more than that in the photograph) and will have to be cut back to match the other fins on the head. However, it will be much easier to remove this excess material than it would have been to fire up the TIG welder again (and then reshape the added material) if I discovered I had not deposited quite enough in the first place. Although I could reconstruct the final broken fin above it at this point, leaving it as-is for now gives me somewhat better access to the lower fin to carve it into final form.

After the larger diameter cutter arrived (a 1/8"-thick 5"-dia. side-milling cutter) I finished removing the rest of the excess Al and then flipped the head over in the vise to check more closely on the underside. The upper "before" photograph shows that the Cu I had clamped to the underside of the fin when welding nicely did its job as a mold for the Al. The new Al extends only ~0.002" below the existing fin. The lower "after" photograph shows the same area after I had spent ~1 minute with a pneumatic file.

[Linked Image]

As can be seen, at this point the "new" fin was still a little too thick, and extended out ~1/8" too far, but it didn't take much more time with the mill, files, and abrasive discs to get it into final form. To form the shape I covered the neighboring fins with two layers of blue painter's masking tape and carefully moved the X and Y of the table to have an end mill follow the curve of the fins. The ~0.01" thickness of the masking tape gave me that much warning if I got too close with the end mill. After getting the outer edge of the fin within ~0.02" of where it needed to be with the mill I finished the job by hand using a pneumatic file.

This only left only the one small section of the fin above it (below it in the composite photograph) to take care of. The next two photographs show the final reconstructed head:

[Linked Image]

[Linked Image]

As a reminder, here's what the broken areas of the head looked like when I started:

[Linked Image]

How I reconstructed these fins certainly can't be the fastest way to do this. But, since I'm not paid by the hour, nor have a deadline for completing it, a methodical approach that employs precision machine tools to the extent possible suits me better than wielding carbide burrs at 20,000 rpm fractions of an inch from other surfaces that I don't want damaged. Plus, doing it the way I do allows me to match details of the fins like thicknesses and taper angles much more precisely than could be done only by hand.

Various nicks and battle scars remain so I'll probably continue to do minor things with the cosmetics from time to time. Also, I still have to decide what to do about restoring texture to the top fins, which already were polished when I bought the machine. But, the head is now ready for the mechanical work.
Posted By: quinten

Re: 1957 BSA Spitfire Scrambler - 02/23/14 11:05 pm

Any plan to texture the repairs ?
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/24/14 11:49 am

Originally Posted by quinten
Any plan to texture the repairs ?
I have three approaches I plan to experiment with, none involving sand blasting, sand paper, or a needle scaler. Two are "high tech" and one "mid tech." However, it has been hard enough the past few months to find time to make straightforward progress with this rebuild without taking time off to pursue these ideas. Since texture of the fins won't be a road block until it comes time to reassemble the engine, I'll likely continue slogging along on the rebuild as I have been doing and postpone starting any of those experiments for a few months.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/02/14 10:25 pm

This post shows what will be required in order to restore a proper sand-cast texture to the fins.

Below are a series of photographs of a small fin (~1-1/2" x 2") broken from a BSA A65 head at magnifications that increase by a factor of ~5x from the top to the bottom. The ruler at the top of the first and last composites has 1 mm marks. In each case the light is at grazing angle and comes from the upper right. The same area is shown each time, with the photographs at the right rotated by ~90-deg. from those at the left.

[Linked Image]

[Linked Image]

[Linked Image]

As can be seen, the directional nature of the texture of some features causes the appearance to change significantly depending on the lighting conditions, which means the texture of a sand-cast head differs in this respect from sandpaper. The reasons it has the texture that it does is the casting sand was very fine grained, the molten Al does not wet sand, and the surface tension of the Al does not allow it to reproduce the texture of the sand at a fine scale. Instead of looking like an impression of sandpaper pressed into the surface, it looks like that of a molten liquid that was flash frozen.

The heights of the tallest features, i.e. the ones that cast the longest shadows with the grazing illumination, are ~25 micrometers (~0.001"). The following micrograph is at much higher magnification, with the smallest features visible in it of size ~1 micron (micrometer)

[Linked Image]

The color is due to the microscopy technique I used to enhance the features (Nomarski DIC), and the lack of focus over the entire image is because the depth of field at this magnification is only a few microns and the small scale waviness of the fin is larger than this. As can be seen, the Al has grain structure down to at least ~1 micron.

What all of this means is that to accurately reproduce the sand-cast texture requires a technique that can apply texturing on length scales from several mm to ~0.001mm, with depths from ~25 microns to 1 micron. Again, although sandpaper can be used to produce a texture, by itself it can't reproduce a sand-cast texture.

As I wrote in the previous post, I have three ideas for techniques that might work to produce texture that is more convincing than is possible by beating sandpaper into the surface, but it will be a while before I will be able to experiment with these ideas.
Posted By: robcurrie

Re: 1957 BSA Spitfire Scrambler - 03/02/14 11:35 pm

The striations appear to be drag marks caused when the mould was removed from the pattern. In mass production, they wouldn't have bothered with smoothing these out as it would be quite difficult in the limited space inside each fin cavity.

Have you tried image stacking to get more depth of field - it works great for macro photography of small details of insects etc.

Rob C
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/03/14 12:12 am

Originally Posted by robcurrie
Have you tried image stacking to get more depth of field - it works great for macro photography of small details of insects etc.
OK, OK. I had shot a series of ~18 photos by changing the focus a micron at a time, intending to create just such a stack. But, then I got lazy and decided just a single one would be fine for present purposes. But, since you made me do it, following is a quick stack of a half-dozen of those photos (uncorrected for illumination):

[Linked Image]
As can be seen, much more of the fin is in focus than in the image I previously posted, but I'd have to be even more ambitious to import and stack the rest, then downsize them for photobucket.
Posted By: robcurrie

Re: 1957 BSA Spitfire Scrambler - 03/03/14 2:32 am

Sorry to push you when you could be using your time more productively (I have folders full of flies eyes that I haven't got around to processing yet).

Any hints for the three techniques you are going to try?
Rob C
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/03/14 4:36 pm

Originally Posted by robcurrie
Any hints for the three techniques you are going to try?
I'd hate to have people tell me they obviously won't work, then try them anyway and discover I should have realized from the start they clearly wouldn't work. So, it's better to do the experiments and only report the (hoped for) successful one(s).
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/08/14 11:46 pm

Other things kept me busy this past week so I wasn't able to make much progress. However, I did measure the valve guides and, no big surprise, found all four of them are worn. I set up the following photograph before I did any measurements incorrectly thinking precision might be needed.

[Linked Image]
I calibrated the bore gage with the precision 0.3125" ring gage that's sitting on the head, but quickly found all four of the guides were bell mouthed by ~0.004" at both ends so precision at the level of tenths wasn't needed. Since it was clear at this point that new guides were in the forecast, and since I wasn't trying to diagnose failure of a component in order to learn from whatever had gone wrong, I didn't spend much time making a thorough set of measurements on the guides.

I used a comparator that also is accurate to tenths (and sensitive to 20 millionths) to measure all four of the valves at several locations each. In contrast to the guides the valve stems show no obvious wear (ignore the reading on the micrometer). So, if I am able to determine these are the original valves I will be strongly tempted to reuse them. Otherwise, I will replace them with high quality modern equivalents.

[Linked Image]

My Irish friend who recently joined BritBike Forum as chaterlea25 built a fine Rocket Gold Star for himself using Colisbro guides so that's likely what I will use as well. However, I just discovered that Kibblewhite doesn’t list valves for A10s so I need to find a recommendation and source for good quality valves. Thanks to chaterlea25 I know the Cylinder Head Shop stocks appropriate items but if anyone knows of a North American source, or has alternative suggestions for types and brands of guides and valves, by all means please post them. It would be great to have a discussion of this topic included as part of this thread.
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 03/09/14 2:57 am

Have you considered k-liners?
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/09/14 8:16 pm

Originally Posted by Allan Gill
Have you considered k-liners?
The advantages of guide liners is they are cheaper (~$1 ea. vs. ~$10 ea.) and seem to be easier and faster to install than actual guides. Also, there appears to be less chance of a catastrophic installation error that could result in a broken head. Unless carefully installed a new guide quite possibly will require cutting the seat, while a liner is much more likely to retain concentricity and thus a quick lap could have the valve ready to go.

All of the above are ample reasons for a repair shop to heavily favor using liners, especially for routine rebuilds (i.e. non-high-performance engines), since the use of labor with a lower skill level, faster turnaround, and lower materials cost all make for lower final cost of the job. However, what I haven't been able to determine as yet is whether or not they are better than (or at least as good as) new guides in general, and for the less controlled thermal environment of air- cooled engines in particular.

The web has been pretty useless for researching this topic. Liner manufacturers and repair shops naturally tout them, magazine writers just repeat what they are told, and posts by home-shop mechanics are all over the place with no good way to judge the competence of writers or the reliability of what is written. Plus, most of the information on the web is about water-cooled engines, which may or may not be a relevant factor.

In my case I am trying to determine "the best" solution to this problem as judged by the actual performance of the valve train, not by the cost or time it takes to rebuild the head (which I'll be doing myself either way). If modern liners really are better, it makes sense to use them, but if instead their only advantage is they are cheaper while still being "OK," no thank you. The jury is still out on this, which is why I am hoping more people chime in with informed opinions, but thus far I'm leaning toward new guides.

Complicating my decision, though, is my quest for originality and the fact the head came from the factory with iron guides. So, should I install new iron guides? Or would an "OK" liner in a reamed original guide be more appropriate than either a replacement iron guide or a modern bronze one? Tough questions to ponder at this point in the restoration.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/13/14 4:44 pm

Although I already know I will have to do something about the valve guides, curiosity got the better of me and I made a few more measurements. I'll leave out details unless someone asks, but the diameters of the valve stems vary by less than 0.0001" along their lengths (even the portion that never entered the guide) so they can be used as a standard for determining the clearance. This means that, instead of separately measuring the stem OD and the guide ID and subtracting (i.e. subtracting two large numbers to get a small number), they can be used to set a gage to measure the clearance directly. This is a more accurate way of doing things.

The next photograph shows the stems of the two exhaust valves trapped between the machined surfaces of a pair of precision V-blocks (the blocks at either side are there just to keep the top V-block from rolling away).

[Linked Image]

The gap between the blocks is precisely the diameter of the valve stems so I used this to 'zero' the split ball gage, which itself is sensitive to 0.0001". In fact, the wear of the guides is large enough that I set the 'zero' at the -0.005" mark to allow a full 0.010" travel.

The guides are 2" long, but the probe on this particular gage is only 1.5" long so it has to be used from both the top and the bottom of the guides to get a complete set of data. However, because the probe is more than half the length of the guides there is overlap of the data in the middle so I can check for consistency. On it you will see paint marks I made every 1/4" as an aid for taking the data.

Next is a graph of the clearance of one of the intake and one of the exhaust valve guides measured with this split ball gage, with the vertical axis the clearance between the valve stem and the guide in units of 0.001":

[Linked Image]

The reason the data for the exhaust valve guide doesn't extend all the way to the bottom is both exhaust guides are enlarged by ~0.01" to a depth of ~1/4" at that end. Also, the "spike" in the clearance of the intake guide near the bottom is real.

As can be seen, the data is consistent with the iron guides presently in the head (which appear to be original) having been originally bored 0.3125" (5/16"), which would have given a clearance of 0.0025" when new. I would have expected the exhaust guides to have suffered more wear than the intake, but there isn't much difference.

If anything, the top of the guide gets more oil than the middle, so the fact the tops of both guides have worn by ~0.003" is due to front-to-back side thrust from the rockers (i.e. ~0.003" more than the ~0.002" clearance they had when new). Since a split ball gage isn't ideal for measuring an oval hole I used a two-point bore gage 1/8" below the top of the exhaust valves and found the front-to-back clearance is ~0.001-0.0015" more than the left-to-right clearance. This is consistent with what would be expected from the direction of thrust of the rocker.

Photographs in an earlier post in this thread show that the combustion chamber and pistons exhibited definite evidence that it was burning oil. However, since valve guides wear slowly and since, almost by definition, any engine runs until something stops it from running, this shows that A10 engines can tolerate at least as much wear as in the above graph.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 03/14/14 3:57 pm

Originally Posted by Magnetoman
. . .Since a split ball gage isn't ideal for measuring an oval hole I used a two-point bore gage 1/8" below the top of the exhaust valves and found the front-to-back clearance is ~0.001-0.0015" more than the left-to-right clearance. This is consistent with what would be expected from the direction of thrust of the rocker.
Another nice write-up Magnetoman, but so far you are only dealing with size. As I am sure you are well aware, a part feature, such as your valve guide bore, must satisfy three types of tolerance to be correct: size, form, and position. The closer the bore is to maximum material condition (smallest allowable size), the less the tolerance of form and position become. As the bore approaches least material condition (largest allowable size) the greater the tolerance for form and position.

A high quality, double ended, go/no-go plug gage with one end sized a couple ten thousandths over the max allowable bore size, and the other end sized at minimum bore size would be a good functional gage in this case, at least to see if the bore has correct form (not oval, or having a curved center axis). In this case, though, you are also dealing with a projected tolerance zone for position. Your bore must coincide with the valve seat.

Most of us mere mortals would pull or drive in the new guide and hope for the best. We would then have to cut the seats to match. I am curious as to how you will deal with that, since you plan to do the work yourself. Also, do you feel that the functional gage i.e. DE plug gage is necessary, or do you accept that the act of honing or reaming will be "close enough". On the other hand, you may have access to a coordinate measuring machine and the ability to use it?

I'm not trying to poke at you here. I have been enjoying your thread and am curious to hear your comments.

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/15/14 12:07 pm

Originally Posted by TR6Ray
… but so far you are only dealing with size. As I am sure you are well aware, a part feature, such as your valve guide bore, must satisfy three types of tolerance to be correct: size, form, and position.
Ray,

Thanks very much for your comments. These are very interesting points to discuss. To restate what you wrote in slightly different words, the ID of the guide has to have the correct diameter and shape (e.g. round, not oval, in cross section and be straight), has to be perpendicular to the valve seat, and has to be concentric with the valve seat. What my previous post addresses is only part of one of these three constraints, i.e. showing that the current guides are worn and so the cross section is no longer the correct ID or shape.

Originally Posted by TR6Ray
A high quality, double ended, go/no-go plug gage with one end sized a couple ten thousandths over the max allowable bore size, and the other end sized at minimum bore size would be a good functional gage in this case, at least to see if the bore has correct form (not oval, or having a curved center axis). … Your bore must coincide with the valve seat.
A go-nogo gage would be a lot better than nothing, but it still wouldn't be ideal all by itself. Imagine if side thrust had caused the guide to wear in the direction of that thrust, but there was no side-to-side wear. The go-nogage you describe would indicate such a guide was fine even though oil could now pass thanks to the wear.

However, a go-nogo gage does add to the information from a split ball gage in ensuring the bore of the guide is truly straight. It's very easy to assume it's straight (after all, it was drilled/reamed with straight tooling, right?), but the important point you make is, what if it is now warped? Your go-nogo gage would provide this information. However, it wouldn't detect that it is oval, nor the groove near the bottom of the intake guide that the split ball gage found. Hence, no single gage provides all of the information that is important to know.

Originally Posted by TR6Ray
Most of us mere mortals would pull or drive in the new guide and hope for the best. We would then have to cut the seats to match. I am curious as to how you will deal with that, since you plan to do the work yourself.
The first step in the decision tree is for me to decide between replacing the guides with new ones (in which case the next step is deciding on what material for those guides), or repairing the guides with inserts (in which case the next step would be deciding on brand and type of inserts). Staying on the first step of this tree takes us back to your first point. Whatever I decide, I need to end up with guides that are perpendicular to the seats and concentric with them. The further away the guides are from "perfect" with both of these tolerances the more material that I will have to remove from the seats, whereas the ideal would be not to have to remove any material at all.

Although the current guides failed the "worn" test, they pass the "perpendicular" and "concentric" tests, as evidenced by symmetric wear on the seats. However, even with worn guides the latter two tests can be done with a gage such as:

http://www.goodson.com/Valve-Seat-Run-out-Gauges/

The real problem is that if someone simply drives a new guide in and then measures it with such a gage, almost certainly they will find a lot of runout. If/when they do, it's basically too late at that point, and a lot of material will have to be removed from the seat to make up for the sloppy guide installation. So, if I decide to replace the guides, what I need is a way to insert the new ones in such a way that the gage subsequently finds minimum runout so the least amount of material has to be cut from the seat.

Instead of pushing guides in from the top and relying on Walt Disney to make them concentric ("wishing will make it so"), Triumph supplied a tool for Tridents that pulls guides into the head using the existing seat to ensure the installation force is concentric with the seat. I have one of these tools and, absent new information coming to light, would either use it, or a variation of it, if I were to replace the guides.

However, before doing this I definitely would measure the holes in the head after removing the current guides to see how concentric with the seat they are. If they are "perfect," and if I pull the new guides into place, the final result is probably the best that would be possible. However, if the holes are not perfect (e.g. say they were tilted by a few degrees), an option to consider at that point would be to remachine them and machine oversize guides to fit the now-larger holes.

If I use inserts I still would want to drill/ream the existing ones to best maintain the current concentricity. The cutting tool will be guided by the worn and misshapen ID of the current guides so there is a limit on how much effect I can have on this. However, I would use the seat and worn guide, and all the measuring tools at my disposal, to set up the head with the spindle of my mill as perpendicular and concentric with the seat as is possible. Having done everything I could to influence the outcome, I would then rely on Walt Disney to "perfectly" guide the reamer through the guide.

Originally Posted by TR6Ray
Also, do you feel that the functional gage i.e. DE plug gage is necessary, or do you accept that the act of honing or reaming will be "close enough". On the other hand, you may have access to a coordinate measuring machine and the ability to use it?
In essence, for present purposes I do have a coordinate measurement machine in the digital readout (DRO) of my mill, supplemented by a variety of sensitive test indicators. I've calibrated the DRO to give me an absolute precision of at least +/-0.0002" over 9" (i.e. the resolution of the readout using calibrated 4" + 3" + 2" gage blocks), so I can determine any x,y,z point on the Spitfire's head with respect to any other point to this accuracy. However, measuring these points will be easier than positioning the head to the same level of precision as I can measure.

As a simple example, say I have the head mounted with the guide pointing up and the center of the guide precisely (+/-0.0002") under the spindle, but the center of the seat is displaced in the X-directly by 0.010" (for simplicity, assume Y is perfect). If I drill the guide under these circumstances I'll then have to cut more than 0.010" from one side of the seat. Since the guide is 2" long and the seat is, say, 1/2" below the guide, to avoid this and make the alignment what it needs to be whatever the head is rigidly mounted to for the machining work "simply" needs to be tilted in the X-direction by an angle tan-1(0.01"/2.5") = 0.23-degrees. That's certainly not an impossible problem, but it's easier to measure a 0.010" offset than it is to adjust a tilting vise or table by exactly 0.23 degrees in an arbitrary direction .

Although I believe what I've described here is the "right" way to do it, I doubt any machine shop would do it this way. They would drive your old guides out with an impact hammer, drive new ones in with the same hammer, cut as much as needed from the seats to compensate for the misalignment, and be done with the job as quickly as possible. Machine shops would go bankrupt doing it the "right" way, which is why I will do it myself. Well, that, plus the fact I very much enjoy this kind of work.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 03/15/14 4:03 pm

Thanks for your response. It will be interesting to see what you decide to do with this. If you replace the guides, I think there would be an advantage to using John Healy's idea of machining away the spring seat side of the old guides and then removing them from the port side. Pete R has also said that he likes to drill the guide bores until the walls are fairly thin before removal to avoid damage to the head.

At least you have the equipment and the wherewithal to do all this.

For my bike, I bought a tool to pull the new guides in. These tools are not very thick on the ground. Most people did not know what I was talking about even after I explained it to them. Other people were out of stock due to low demand. "Nobody uses those things," they said. The one I ended up with did not work well. It looked like this:

[Linked Image]

Since you have the capability, you could do better by making your own. The center rod that came with my kit was too large in diameter to fit through the new guide. We used an external hone on the rod until it was a fairly loose sliding fit. Problem was that we had heated the head in an oven. In use, the heat transferred quickly to the guide which closed in and seized on the rod. In a bit of a panic, I kept tightening the puller till the rod broke. That was not a good day. You can see in the picture that they included a guide drift with the kit. That is how that first guide got seated the rest of the way after the puller broke. The drift was seemingly made of butter, and was done after one use.

Here's hoping you have better fortune.

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/16/14 11:40 am

Originally Posted by TR6Ray
I think there would be an advantage to using John Healy's idea of machining away the spring seat side of the old guides and then removing them from the port side. Pete R has also said that he likes to drill the guide bores until the walls are fairly thin before removal to avoid damage to the head.
Pushing out from the port side also is reasonable if one first machines away everything that is projecting so no carbon deposits are dragged though to score the bore. While reducing the wall thickness is a good idea, enough has to be left behind to catch the shoulder of a drift to allow the remains of the guide to be pushed through. Also, if too thin the wall could "buckle" to some extent when pressed by the drift, increasing its diameter and somewhat defeating the purpose of reducing the diameter. One of my boring heads is adjustable to 0.0001"-dia. and takes a boring bar that is small enough and long enough remove the guide entirely from the inside out if I decide to do that. However, I expect it won't be necessary to do that.

Originally Posted by TR6Ray
I bought a tool to pull the new guides in. These tools are not very thick on the ground... Problem was that we had heated the head in an oven. In use, the heat transferred quickly to the guide which closed in and seized on the rod.
In my previous post I wrote that I have Triumph's own version of the tool you show, that they supplied specifically for Tridents and Rocket 3s (BSA part no. 61-6063). The tool has several pieces and looks essentially like the aftermarket version you have. However, as you found, the combination of a cold guide and a hot head allows the guide to slip easily into place only until thermal expansion causes the guide to "seize." The limitation of the Triumph tool is it takes so long to assemble and position the tool that it's impossible to keep this from happening, which means losing all the advantage of thermal expansion. I hinted at my actual plans when I wrote that I "would either use [this tool], or a variation of it, if I were to replace the guides." If the "variation of it" I have in mind works, I'll post details of the tool.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 03/16/14 2:13 pm

Originally Posted by Magnetoman
I hinted at my actual plans when I wrote that I "would either use [this tool], or a variation of it, if I were to replace the guides." If the "variation of it" I have in mind works, I'll post details of the tool.
Sorry, I did read that, but went off on a tangent. I'll continue to follow this with interest (and pay closer attention).

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/17/14 4:58 pm

Originally Posted by TR6Ray
Sorry, I did read that, but went off on a tangent...
Hey, I don't carefully read what I write so I can't expect anyone else to…

Two months ago I had almost started with the gearbox when I got diverted by the head. However, with the welding and reshaping now done, the head is at a place where I can set it aside without problem. Because of too many commitments I have to make (slow) progress by dealing with bite-size jobs like this, so I'm planning to return to the gearbox. This means that, unless someone beats me to it, the intimate details of the rare SCT2 will be revealed for the first time.
Posted By: Peter R

Re: 1957 BSA Spitfire Scrambler - 03/18/14 5:13 am

Concerning removal of old valve guides, here is a trick I leaned a long time ago :

Tap a screw thread in one end of the guide, and insert a short bolt, then use a long drift to tap out the guide from the other end. (drift resting on bottom of the bolt)
With this method you stretch the valve guide a little, making removal easier wthout causing any damage.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/18/14 4:07 pm

Peter, that's a valuable technique that is worth saying a few more words about. The reason it works is due to two materials parameters of the guide: compressibility and Young's modulus.

If you push or pull on a piece of metal you compress or elongate it, and it doesn't take a huge hydraulic press to see an effect. If you've ever clamped something in a vise to do precise machining on it (i.e. so you had a dial indicator on one jaw) you know that the force you exert on the handle is sufficient to compress the metal by a measurable amount. Similarly, some specs for tightening the big end of a rod call for measuring the stretch of the bolts to determine when enough torque has been applied. These bolts are high strength steel 5/16" or 3/8" dia. and a few inches long, and the stretch is ~0.005". Again, this shows the force you exert using only a wrench stretches the bolt by a measurable amount. How much a metal compresses or stretches with a given force is its compressibility.

If you pull on a piece of modeling clay (or pizza dough) it shrinks in cross section. Metals do the same, and the amount by which the dia. of a rod changes for a given change in length is Young's modulus. For the metals we care about this modulus is ~1/3. That is, if you stretch a bolt by 0.006", its diameter decreases by ~0.002".

OK, now to guides. If you push on a guide with a standard valve guide removal tool you will compress the guide and therefore cause it to expand. Because of the geometry and configuration calculating how much it will expand would be complicated, but just from the examples in the previous paragraph it should be clear that the amount won't be negligible. That is, we are dealing with interference fits of a few thou., so expansion by even a few tenth-thou. makes matters worse. However, using a method like Pete describes would stretch the guide, thereby shrink its diameter by a non-negligible amount and make the job of removal easier.

It's possible to have the best of two separate removal techniques. First, machine away the guide that projects into the inlet port in order to remove all carbon that could score the head as it's pushed through. Then drill the guide from that end to reduce the wall thickness and relieve as much tension as possible. But, don't run the drill all the way through to the other end. Leaving the portion that extends into the rocker box alone will produce a step in dia. inside the guide, so now a drift made to the dia. of the drilled portion can be used with a press to push the guide out from the port end.

You can do more with a big hammer plus science than you can with a hammer alone…
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 03/18/14 4:39 pm

On the k liners, I have had no issues using them but they need to be fitted by a good machinist. I would happily use them on another head, the person who recommend them to me has done thousands of miles on his bikes which have them fitted.

Changing note,

Have you straightened any fins on Your head? I was interested to know what practices you have used. I have a bent bottom fin on my A65 head, thankfully it hasn't showed any signs of cracking yet.

Thanks and keep up the good work. It's been a great thread to follow.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/18/14 10:47 pm

Thanks very much for your nice comment. I appreciate it.

Originally Posted by Allan Gill
On the k liners, I have had no issues using them but they need to be fitted by a good machinist.
I've been collecting reports on liners and there are a few troubling ones. However, the problem is that it isn't possible for me to determine if failures people reported were due to some intrinsic weakness of liners themselves, or due to improper installation. A big factor in me putting the head aside for now is to give me more time to agonize over this choice. A liner would let me preserve more of the original head, which is a big factor in my restoration decisions, but a new guide would eliminate any concern about possible failure. What to do, what to do...

Originally Posted by Allan Gill
Have you straightened any fins on Your head? I was interested to know what practices you have used. I have a bent bottom fin on my A65 head,
No, but thanks to a generous member of the forum I have a sacrificial A65 head that I've used for various experiments. When I needed a sample for my microscope to examine the texture as shown in a previous post, I snapped a fin from the head. The Al alloy wasn't weak, so it resisted being removed, but it showed no sign of ductility at all. It snapped like a dry twig in the desert, or a piece of plate glass. So, if you don't have the facilities to restore a broken fin, I suggest you leave your bent one as-is.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/24/14 6:00 pm

Thanks to someone who recently contacted me outside of this Forum I have some interesting new information on the SCT2 gearbox. Since I intend for this thread to include every bit of information that can be found on the 1957 Spitfire this post contains that information (which also is relevant for the history of Gold Stars).

I posted the following chart earlier in this thread, but have copied it here for convenience:

[Linked Image]

It turns out Service Sheet 21A from August 1956 lists components for an SCT2 gearbox with needle roller constant mesh gear (gear A in the chart above). Although the chart shows the SCT2 was used only for the 1957 Spitfire, Service Sheet 21A doesn't mention the Spitfire at all and instead says it would be for Gold Stars built to scrambles specification starting with engine numbers DB32.GS.847 (350 cc) and DBD34.GS.2001 (500 cc). This is interesting for several reasons. One is that the SCT2 never ended up being used in any Gold Star, with them having to settle for the SCT and ASCT. Another is that although DBD scramblers are described in this 1956 Service Sheet as an intended recipient of the SCT2, DBD motors were not used in scramblers until 1958.

Service Sheet 21A further says that gear H of the SCT2 is 42-3082, whereas the above 1963 chart shows it to be 42-3210. However, this discrepancy is resolved by the 1963 Master Price List which says the original gear was superseded by 42-3210. Unfortunately, since 42-3210 also was used in the SCT and STDT, still missing is information to know if this substitution was made before production of Spitfires began several months later, in the middle of Spitfire production, or sometime later. Also, since there is no way of knowing if whatever 'H' gear I will find in my own gearbox is original, absent markings on it, only by comparison with a known 42-3210 would I be able to tell.

For ease of comparison of the SCT2 with the SCT (and RRT2), I extracted the following chart from the one above and added a few notes:

[Linked Image]

Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/29/14 9:36 pm

Update on Part Numbers
As an update to my previous post, note that the 1963 chart from BSA's east coast distributor shows the RRT2 with different part numbers for its mainshaft and sleeve gear than its SCT2 fraternal twin, even though both use 25-tooth sleeve gears with needle bearings. The puzzle of why they would be different was somewhat resolved when I learned after my previous post that a 1956 factory diagram of the RRT2 shows it with the same numbers for these two parts as the SCT2. However, what the precise differences that were introduced later remain to be figured out. At this point I can only speculate that sometime a year or more after its introduction a small change was made to the RRT2 resulting in new numbers, and that the 1963 chart only shows that later version.

Returning to gear H, it was 42-3082 when the SCT2 was introduced in 1956, and still was this number in the 1958 parts list, but was 42-3210 for both the SCT2 and the SCT by the time of the 1963 chart. However, I now have learned the change came for the 1961 model year. Parts Service Bulletin N2 "New Components for 1961" of November 1960 lists 42-3210 for "B34 scrambles." From this we can see the new gear was improved in some way over the old one and substituted for it as a replacement as well as for new production.

SCT2
The next picture is the gear that makes the SCT2 the fraternal twin of the RRT2, and makes these two different than any of the 'T' gearboxes (e.g. SCT):

[Linked Image]
The Torrington B-1314 needle bearing extends in 7/8", followed by a short gap, followed by a bush that is 1-1/8" long. As mentioned at the top of this post although this gear should be identical to the one used in the RRT2 some small variation I am still trying to identify resulted in a different part number for the RRT2 by the end of production in 1963.

The other component that distinguishes a 'T2' gearbox from a 'T' is the mainshaft on which runs the above gear:

[Linked Image]
As can be seen there is a short scroll (~0.37" between its outer edges) roughly in the middle of the straight section of this shaft. When the sleeve gear is on the shaft the left edge of this scroll is aligned with the outer edge of the bush and the right edge is ~1/3 into the bush. The way the helix is cut any oil that makes it through the needle bearing and the initial 2/3 of the bush then would be pumped the rest of the way through the bush, and out onto the ground. As discussed at the end of this post I will make more careful measurements in the future. However, for now, the shaft under the sleeve gear is 13/16" diameter.

For reasons I don't remember I have most of two disassembled STD gearboxes in a box in my garage. This made it convenient for making some comparisons. Something 'T2' gearboxes share with 'T' are needle bearings at both ends of the layshaft, whereas non-'T' use bushes in both locations. The next photograph shows the central casting (the one with the gearbox code stamped into it), with the SCT2 on the left and STD on the right. The OD of the hole in the casting for the needle bearing is 1" while that for the bush is 15/16".

[Linked Image]

The next photograph shows the SCT2 layshaft at the bottom and the STD at the top:

[Linked Image]

The most obvious visual difference is the STD has a scroll in the end of the shaft that goes into the housing (at the left of the photo). Both of these shafts are worn, and they weren't necessarily made to the nearest 0.0001" in the first place, so some educated guesswork is required to determine the dimensions that would have been on the engineering drawings, i.e. the dimensions they would have had when new if made by a skilled machinist using tooling in excellent condition. Marked with letters are the four places where I measured the diameters of the shafts:

____SCT2_______STD
A__0.6871"_____0.6840"
B__0.9985"_____0.9982"
C__0.9885"_____0.9915" (this is a machined, not a ground, surface)
D__0.7498"_____0.7482"

Although I made the measurements to 0.0001" accuracy, the values above need some explanation since both shafts are worn. Wherever possible I made the measurements on areas that showed the least wear. Also, I made a number of measurements in each region and the above are the largest, repeatable values I found. That is, these are the diameters where the measurements indicated the shafts had the least wear. It appears from these measurements that regions B and C were made to the same set of specifications on both shafts, with the differences in region B due to different amounts of wear plus the tolerances when they were originally made. Region C is a machined surface, not a ground one, so it wasn't made to great accuracy in the first place and the differences are due to manufacturing tolerances.

Regions A and D are made for bearings (SCT2), or for bushes (STD), with a gap required for the latter to allow a cushioning film of oil. Doing my best to correct for the unknown amounts of wear, it appears to me that BSA aimed for their non-'T' shafts to have diameters 0.002" smaller than their 'T' shafts. Put another way, if you are installing a new bush in a gearbox with non-'T' shafts, measure the OD of the shaft and then ream the new bush 0.002" oversize after installation.

Another difference I found was with the pressed-on gear B. In the following composite the edge of the layshafts of the SCT2 (top) and STD (bottom) are aligned with each other which makes it apparent the gear isn't pressed on as far on the SCT2.

[Linked Image]
The reason for the difference can be seen as due to a ring that was placed on the shaft to precisely position the SCT2 gear, whereas the STD relies on the less precise slope of the end of the broached slots to do this. The difference in positions of the gears on the shafts also can be seen in the next photograph.

[Linked Image]

Not surprisingly, there are various wear issues to deal with. As an example, when I disassembled the gearbox I found three washers on the back of the stop for the kickstarter quadrant when there only should be one. Too many washers is seldom a good sign. The next photograph shows that the hole for this stop (the center hole) is elongated.

[Linked Image]

The nut holding the stop must have been loose for quite a while, allowing the stop to elongate this hole every time the kickstarter returned to the top of its travel. Since this hole is in the casting stamped "SCT2" swapping it for a different casting isn't an option. I'll either build it up with my TIG welder and machine back to size, or machine it slightly oversize, press in a plug, TIG weld it into position, and machine a new hole. The second of these approaches would take somewhat longer.

Plans for Immediate Future
Having non-'T', 'T', and 'T2' gearboxes gives me the rare opportunity to compile detailed information on their similarities and differences that I've never seen anywhere else (only a fraction of which is in this post). Unfortunately, this will slow down my actual restoration work on the Spitfire because now I'll have to disassemble my ASCT as well. Which means soon all available workbench space will be covered by disassembled gearboxes.
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 03/30/14 6:04 pm

HI MM,
The STD shaft in your last post should have the wire circlip to locate the gear in position.
Here is a link to a repair and strenghtening modification that I have done on several gearboxes, (no more issues)
http://www.a7a10.net/forum/index.php?topic=2914.msg19637#msg19637

The high speed gear on the RRT2 box I have apart has multiple engagement slots rather than the 6 dog/hole engagement on your SCT2,

I have a new layshaft from autocycle engineering if you need measurements for comparison but can only measure to ).001in or 0.01mm

Regards
John

Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/31/14 3:26 pm

Originally Posted by chaterlea25
The STD shaft in your last post should have the wire circlip to locate the gear in position.
That's good to know. If I had as much experience with pre-unit gearboxes as you do I would have recognized this difference as due to the bodge by a previous owner. This illustrates why it is never a good idea to base a conclusion on only one data point . My box of parts has two incomplete STD gearboxes with neither mainshaft and only the one layshaft that is lacking the circlip. This is why the STD currently resting in the Spitfire will be coming apart for study along with the ASCT.

Originally Posted by chaterlea25
Here is a link to a repair and strenghtening modification that I have done on several gearboxes, (no more issues)
http://www.a7a10.net/forum/index.php?topic=2914.msg19637#msg19637
Yours is an excellent modification that is very well executed. It nicely illustrates why I recommend anyone in the vicinity of the British Isles should get you to do any mechanical/machining work they need as you did for my BSA that lives in Ireland. Unfortunately, though, my self-imposed restriction of restoring this Spitfire to a condition every bit as bad… er, I mean, to the identical quality as it left the factory with doesn't allow me to copy your modification.

Originally Posted by chaterlea25
The high speed gear on the RRT2 box I have apart has multiple engagement slots rather than the 6 dog/hole engagement on your SCT2,
Here's a photo of the RRT2 sleeve gear and its mate that John sent separately:

[Linked Image]

This resolves the mystery of why a different part number was used for the gear in the later RRT2 from the one it had when introduced in 1956. The above photograph shows it wasn't due to a minor modification. The initial RRT2 gearboxes used the same gear, with the same 6-dog arrangement, as for the SCT2 shown in my previous post in this thread. However, having 6 slots means it has to rotate as much as 60-deg. to engage the dogs when upshifting. Having 18 in the later RRT2 reduces this rotation by a factor of 3. The longer lag because of the fewer number of slots probably was unacceptable to road racers but by the time this modification was made the SCT2 was no longer in production so the later gear wasn't listed for it as a retrofit.

Originally Posted by chaterlea25
I have a new layshaft from autocycle engineering if you need measurements for comparison but can only measure to ).001in or 0.01mm
Thanks for offering to make the measurements, but my interest is in how good/bad BSA made their components on their old equipment.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 04/13/14 11:20 pm

I was away for the past ten days, returning home late last night, so I've made no progress on the Spitfire since my last post. However, I did finally cancel a trip to Ukraine in May so now that won't take a couple of weeks out of my restoration schedule like the recent one did.

Due to really poor planning on my part, on my way back from Europe earlier this week I had to give another talk in North Carolina. However, encouraged by someone who is a mutual friend with the owner, I used that as an opportunity drive a few hundred extra miles to visit the 'Wheels Through Time' museum in Maggie Valley.

Dale Walksler has amassed -- given the size of his collection, that's an appropriate word -- an amazing collection of rare early (and later) American motorcycles. I only had two hours to spend which was barely enough for Dale to scratch the surface of the museum's content. However, a particularly interesting (to me) observation came when he was showing me his restoration shop. I commented on the absence of a lathe, mill and TIG welder. He explained he didn't want to spend the time to learn to do things that he could have experts do for him, and besides he much preferred to restore motorcycles using original parts rather than to fabricate things. Given how many of his motorcycles are ~100 years old, the fact he is able to find so many original parts to use is a testament to his deep contacts across the country.

This visit highlighted the difference between assemble vs. restore "philosophies" (both are "restorations," but I can't think of better words to draw the distinction). Dale's approach is at one end of this spectrum, while mine with this Spitfire is at the other. My approach produces finished machines at a much lower rate (which Dale commented on), but most of us do these things for the personal satisfaction they bring so there isn't a 'right' or a 'wrong' approach.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/01/14 5:31 pm

I finally found a little time to work on the bike. Post #535524 above shows the elongated hole for the kickstarter stop which I plan to fill in with weld and re-drill. However, before doing the welding I have to be able to accurately locate its position in order to know where to drill the hole again.

The hole for the stop is not in line with anything else so a bit of work is required to determine its position. The next photograph shows two measuring setups in one, using the casting from an STD gearbox mounted on the bed of my mill.

[Linked Image]

I machined the two Al pieces shown in the steel bushes to make it easy to tram the centers of those two bushes in line with the X-axis of my mill. In principle I could have done this using the bushes themselves, but they have different IDs and they are located below the height of the gearchange quadrant so it would have been a lot of extra effort to do it that way. So I accurately machined the two Al pieces to be slip fits in the bushes and for the height for the dial test indicator (DTI) at the left in the photograph to clear the quadrant. I machined them with stepped diameters because I thought it would be easier to tram using a straight edge, but that turned out not to be necessary. These Al pieces allowed me to use the DTI at the left in the photograph to position the line connecting the centers of those two holes parallel to the X-axis to within better than ~0.002" over the 5" spacing between the holes. After having trammed the case, clamping it down, and checking to be sure nothing moved, that DTI was removed.

Next was to locate the position of the kickstarter stop hole with respect to the closer of the two steel bushes. Since the SCT2 case is a rare one, here it was 'measure thrice (or more), cut once.'

The first measurement was to put dowels in the two holes, measure their outside separation with calipers, and subtract the sum of their radii. This gave 0.938", i.e. 15/16". However, aside from any question of absolute accuracy of this technique, it does not give the orientation of the hole.

A second technique was to use the 'find center' function of my mill's digital readout (DRO) to determine the centers of the two holes. The differences in X and Y of the centers determine how far to move from one hole to get to the next. However, even though my DRO gives dimensions to a precision of 0.0002", the accuracy for this particular measurement isn't nearly that good because the hole for the stop is somewhat oval. This is an example where analog is a lot better than digital.

The third technique was to find the center of the holes with the DTI shown mounted in the mill's spindle in the photograph. The steel bush was very close to round so, with the Al piece removed, I was able to determine its center to better than 0.001". I zeroed the DRO and then moved to the hole for the stop. Because that hole isn't perfectly round the needle of the DTI didn't stay in a fixed position no matter where I located the hole with respect to the spindle. Instead it swung by ~0.005" even when in the "best" location. However, by mentally averaging those swings I estimate that I was able to find the geometric center of the hole to within ~0.002".

With the centers of the two steel bushes aligned along the x-axis, then zeroing the DRO at the center of the closer steel bush, the center of the hole for the stop in this casting is at X = 0.9268", Y = 0.1186". According to the Pythagorean Theorem this means the center of the hole is a distance 0.9344" from the bush, i.e. 0.003" less than a nominal 15/16". This is only slightly outside my estimated measurement error, and in any case is probably within the precision the part was made in the first place. It is located at an angle theta = tan^-1(0.1186"/0.9268") = 7.29-deg. with respect to the line connecting the two steel bushes. I have no idea how BSA decided on this, other than that the draftsman placed the hole on the drawing where it seem to fit best.

Although the greatly elongated hole in the SCT2 casting will limit the precision, I'll check that casting the same way anyway before welding to make sure there are no surprises. After that I'll weld up the hole. Once welded, the above tells where to drill it again.

Addendum: I retrammed and remeasured several times tonight, picking different depths into the holes each time for determining their centers. Averaging the results and rounding up from the ten-thousandths values I get X = 0.930" and Y = 0.120". With these values, which I plan to use, the distance will be only 0.0002" (two ten-thou.) longer than a nominal 15/16".
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/06/14 6:36 pm

As I wrote in the previous post, before welding up the hole for the kickstarter stop on the SCT2 inner cover I needed to be sure it is located in the same position as the one that I had measured on the STD. It is. However, it is quite apparent that the hole for the needle bearing isn't in the center of the boss. Although not as obvious at first glance, the ball bearing isn't in the center of its boss, either. This is shown in the next photograph, with the STD gearbox at the right.

[Linked Image]

If these holes are in the wrong positions the shafts will be misaligned, which would be a major problem. To check for this I installed one of the Al spacers from my previous post in a vise and photographed the two covers with my camera on a tripod to ensure the perspective of the two shots would be identical. Briefly, I used PhotoShop's "find edges" function to trace the edges of the STD cover in red, made the rest of the image transparent, and overlaid it on the the SCT2 cover. This is shown in the next photograph (in green are remnants of the STD cover that weren't made transparent).

[Linked Image]

As can be seen, although the SCT2 casting is displaced slightly to the left of the STD, all of the holes in the two are in excellent alignment. This can be better seen in the enlargement below.

[Linked Image]

The large steel bush in the center (along with the other one in which the kickstarter pivots) is what aligns this cover with the main housing so what matters are the positions of all of the other holes with respect to these two bushings. As this enlargement shows, although the overall casting of the SCT2 is displaced sideways by ~2 mm with respect to that of the STD, all of the holes in both castings are in identical positions.

Likely a multi-spindle drill press was used to make these holes and the casting from my SCT2 was simply clamped on the bed in a slightly incorrect position (or the jig into which it was clamped wasn't properly positioned). In any case, this cover is now ready for welding.

Unfortunately, the region of the mainshaft under the sleeve gear is in very rough condition and I'm still investigating ways to try to recondition it. When a shaft runs in a bronze bush and the softer bush eventually wears it can be cheaply replaced. However, since a shaft has to be hardened to work with a needle bearing, if (when) something goes wrong and the shaft gets chewed up the problem can't be solved by simply installing a new bearing. So, if anyone has an RRT2 mainshaft in decent condition that they are willing to sell, please send me a PM. Thanks.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/11/14 11:20 pm

While waiting for the reproduction RRT2 mainshaft to arrive from Autocycle I made some measurements on the SCT2 shaft that will be needed if it is to be restored. The first problem to overcome is the centers at both ends had become somewhat distorted over the years by wayward hammer blows. If the shaft itself was perfectly straight and round it would be no problem to touch them up with a 60-deg. center drill. But, of course, nothing is ever that easy.

The issue with recutting the centers is illustrated by the next photograph. It's no problem to center any smooth surface on the shaft to less than 0.0002" Total Indicated Runout (TIR), but what to do if surfaces that should be cylindrical aren't?

[Linked Image]
It's not just that wear has resulted in a slight taper to this section of the shaft, the roughness is uneven making any given cross section slightly oval (not actually oval, but not-round). As will be seen later, the other end of the shaft was much less difficult and I got the TIR to 0.0005".

After several attempts with the shaft held in the chuck at different points, I obtained the best result when I chucked it on the 1" nearest the taper and then centered it on the end of the taper, as shown in the next photograph.

[Linked Image]
As the indicator shows it was easy to get the TIR to 0.0004", i.e. to center that particular section of the shaft to half that. I already knew from previous attempts where I had used other portions of the shaft that it was slightly bent, so there was no point doing better than this.

After having recut the center at this end of the shaft by holding it on one section while "zeroing" it at the end of the taper, when moved to a precision bench center that same end of the taper now has a TIR of 0.002". That is, its center of rotation is offset from the center's center of rotation by 0.001". This is shown in the next photograph.

[Linked Image]
It might not be obvious from the information given so far, but the reason for the issue with the shaft is it is slightly bent. This can be seen from the data in the next photograph, with values of the TIR below the points on the shaft where I measured them. Values in blue indicate the center at the left end is offset in the opposite direction to the one at the right.

[Linked Image]
If the center at the right of an ideal shaft were simply offset from the true center the values of TIR would rise linearly from left to right. Instead, as can be seen by extrapolating the data to the ends of the shaft, the centers are concentric with the ODs at the ends to better than ~0.001". However, as also can be seen, the region directly under the sleeve gear is bent away from the centerline by ~0.002" (i.e. TIR of ~0.004").

While these values might seem small, the bend adds to the difficulty of restoration. But, before doing anything more permanent than measuring the shaft, I'll wait until the RRT2 arrives from England.
Posted By: L.A.kevin

Re: 1957 BSA Spitfire Scrambler - 05/14/14 5:27 pm

Just out of curiousity, why use the centers at all? I work with rotating equipment a lot, and centers are used functionally, and because of that, I always require inspection with v-blocks. A magnetic V block or a V block with a clamp gets rid of the guess factor of whether the part is orbiting on the center.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/14/14 9:43 pm

Originally Posted by L.A.kevin
Just out of curiousity, why use the centers at all?... I always require inspection with v-blocks.
Good question. I have precision V-blocks and a surface plate so that's a straightforward measurement. However, the issue for me isn't so much to determine if the overall shaft is rotating on center (i.e. whether it's bent), but rather how to repair the damaged bearing surface. The only way I can think to do this is to turn the shaft between centers on my lathe, and to do that requires restoring the centers as accurately as I can despite only having a chewed up surface to grip it with at the drive end.

In operation the position of the drive end of the shaft will be determined by the sleeve gear, not by the center in the end of the shaft. Because of the slight bend (i.e. an angle of arctan[0.002"/1.7"]), using the location where the restored center at the drive end is currently located means the sprocket on the ~7"-dia. clutch hub will oscillate in and out by ~+/-0.004". However, given the various precisions and tolerances this machine had even when new, I'm counting that as perfect.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 05/14/14 10:28 pm

MagnetoMan, I am sure you have a plan in mind and maybe you already told us but I overlooked it. Are you going for an undersized bearing diameter that runs true? Are you going to maybe plate the bearing surface with hard chrome and then take it to size? How hard is the shaft right now?

I have run thousands of shafts of all shape and size between centers on an external grinder. They were all cut first on a lathe, leaving grind stock for after heat treatment. Once they were case hardened, and usually slightly distorted from that process, they came to the grinder to be cut to finished size, typically holding a tolerance of +/- .0002"

Something here is not making sense to me if you are trying to put this worn shaft between restored centers and then start turning it on your lathe.

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/14/14 11:20 pm

Originally Posted by TR6Ray
Are you going to maybe plate the bearing surface with hard chrome and then take it to size? How hard is the shaft right now?
This was my original hope but I contacted several hard chrome platers and was advised that it wouldn't hold up to the pressures it would be subjected to by the rollers.

Originally Posted by TR6Ray
Something here is not making sense to me if you are trying to put this worn shaft between restored centers and then start turning it on your lathe.
My plan is to make my own custom hardened inner track, like the ones Torrington sold (sells?) for this purpose but longer.

Ideally, I would make the sleeve as thin as possible using the appropriate steel, send it out to be case hardened (or, I do have an old can of Kasenite so do-it-myself isn't off the table), measure its ID after this process, turn the shaft between centers to ~0.001" larger than this, cool the shaft and heat the sleeve and press on, then grind the OD of the hardened sleeve to the proper diameters for the bearing and the bushing.

Since the hardening will introduce dimensional changes that I can't predict, and since there will be a fee for doing this independent of the number I have done in a batch, I'll make a few with slightly different IDs and ODs in order be able to select the best one. I might have to make a mandrel to clamp the OD while I hone the ID to make it round after heat treating, but once I have the sleeve ready I'll cut the OD of shaft to match.

I have the necessary instruments to measure the sleeve ID and the shaft OD to 0.0001". The TIR of my lathe is less than 0.0001" as is the spindle on my Dumore toolpost grinder so I should have the necessary precision to grind the OD to what is needed.

Anyway, that's the plan.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 05/14/14 11:50 pm

Thanks. As I said, I was sure you had a plan. It will be interesting to see how this works out, to say the least!

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/15/14 12:12 pm

Originally Posted by TR6Ray
I was sure you had a plan. It will be interesting to see how this works out, to say the least!
Hmm, didn't they say the same thing to Gen. Custer when he headed out for the Little Bighorn?...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/18/14 6:31 pm

On May 8 I ordered a reproduction RRT2 mainshaft from Autocycle Engineering and only nine days later (yesterday) it appeared in my mailbox. In a previous post I noted that both the SCT2 and RRT2 used the same mainshaft when the two were introduced in the summer of 1956, but the part number for the RRT2 was later superseded by another. So, even if it turned out to be of good quality, whether or not the reproduction RRT2 even would work wouldn't be completely certain until it arrived and I was able to measure it. As described below, the reproduction RRT2 is of excellent quality, and it does fit.

I'm not going to bother photographing the RRT2 and uploading it because it looks identical to my SCT2 (other than the battle scars). Overall it is a gorgeous piece of machining.

Rather than posting all the dimensions and specifications, I'll only note the critical ones. The Torrington catalog calls for the diameter of the shaft under the needle bearing to be within +0/-0.0005" with any taper along that section to be less than 0.0003". The hardness of the shaft needs to be 58-60 on the Rockwell C scale, and the rms roughness has to be no greater than 8.0 micro-inches. Further, there has to be a 0.002"-0.003" step to a smaller diameter (larger clearance) for the bush that fills the other half the sleeve gear.

To check the splines I slipped the sliding gear on the portion of the shaft where it should slide, and it did without any feeling of roughness, tightness or looseness. I don't have a specification for the clearance needed for the other gear but the diameter of the reproduction shaft is 0.0003" smaller than my old one (i.e. it is 0.9983"). That difference is small enough that it is difficult to feel any difference in play between the new and old shafts, so I'll count this as meeting specifications. The press-fit gear engaged the splines as it should but won't go into place until I install it in my press. Held between centers the Total Indicated Runout (TIR) everywhere along the shaft is between 0.00025" and 0.0003", which is tiny. So, the reproduction shaft passed all of these tests.

Where the shaft should be 13/16"-dia. for the needle bearing, it is spot-on at exactly 0.8125", with no variation in diameter along that section. That is, it meets these specifications. To get the most accurate measurement of the small step to the diameter for the bush I used a comparator with resolution 0.00005" (half of a ten-thousandth). The step height is 0.0023", i.e. if the bush is reamed to a perfect 13/16" it will have that much clearance for the oil, which meets BSA's specifications.

The final two important specifications the shaft must meet for use with a needle bearing are the hardness and the surface finish. Since it would be a bad idea to put an indentation in the bearing surface, I measured a spot on one of the adjacent splines. I found Rockwell 60 +/-1.5, which meets specifications. However, the surface finish isn't quite correct. The bearing manufacturer calls for no greater than 8.0 microinches but I measured a consistent 15-16 microinches at various locations on the bearing surface. However, of all the specifications that the shaft could have failed to meet, this is by far the easiest to correct. I could remove as much as 250 micro-inches of material (0.0005" in dia.) in polishing it and it still would meet the diameter specification, but all I need to remove is ~8 micro-inches to achieve the necessary smoothness (anyone who knows about the difference between rms and peak-to-peak needn't comment on it, unless they feel compelled to).

Thanks to the excellent machine shop Autocycle used to produce this part I have a fine reproduction mainshaft that fits and is identical in every way I can tell to the damaged shaft. Given my desire to refurbish and use original parts wherever possible, if I knew for sure the damaged SCT2 mainshaft was original I would face a dilemma. However, since I don't know if the mainshaft that came with my SCT2 gearbox is original or not (i.e. if it was shipped with the gearbox, or is a later replacement with the part that superseded the original), the current one will be going into a box along with my notes on how to repair the damaged section.

Having a high quality reproduction mainshaft in hand is going to save me many hours of work. The only remaining major task with the gearbox is to weld and remachine the oval hole in the center gearbox case. I hope to find the time for that next weekend.

p.s. A few hours after uploading this current post I transferred the circlip from the old mainshaft and pressed the gear onto the new one. It went into place without problem. Again, aside from the easily solved issue of the surface finish being slightly too rough this is an excellent piece of machining that meets all other specifications. Since not everyone is equipped to measure surface finish I'll send an email to Autocycle to bring this to their attention.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 05/19/14 10:22 pm

Good move there, Magnetoman. Autocycle Engineering sounds like a class outfit. It's nice when you order something and get what you paid for. That is some impressive inspection and feedback on your part.

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/22/14 12:15 pm

Originally Posted by TR6Ray
That is some impressive inspection and feedback on your part.
Thanks for your comment. I haven't heard back from Autocycle but I wouldn't be surprised if they rely on the machine shop's self-inspection so they should be happy with this independent assessment (if I were them I would forward the information to the shop and wait to hear their comment before responding).

Related to this, I've now heard from two additional places that specialize in hard chrome plating and in spray metallization. This brings to total to at least 6-7 firms and, with one exception, all have told me that neither of those processes will stand up as a bearing race (it would be fine to increase the OD of a worn shaft to fit the inner race of a, say, ball bearing). The 2-3 that made suggestions of what will work all said a hardened sleeve is the only way to make a repair. I mention this because someone might send off a shaft to be built up by one of these processes without telling the company what the intended use will be and get back a shaft that would then fail.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/26/14 9:44 pm

With the SCT2/RRT2 mainshaft under control, the remaining major repair to the gearbox is the elongated hole for the kickstarter stop:

[Linked Image]

Two approaches to this repair come to mind: 1) fill it with weld and remachine the hole, or 2) weld a new piece of Al in place and machine the hole in it. Unfortunately, the problem with approach #1 is that the hole is of fairly small diameter and relatively deep so getting both filler metal and an electrode at least halfway down inside without sticking the electrode to the wall (more than once…) is, let's say, problematic. But, upon reflection, solution #2 should have been #1 from the start because the repair would end up being made with a piece of fully hardened 6061-T6 rather than relatively soft 4043 filler. Even though the ends of the 6061 would be annealed by the welding, most of it would remain in the fully hard state.

This hole started life as 7/16" (0.4375") so I first reamed it 12 mm (0.4724") but that still left too much of the elongated hole. Moving up to 12.5 mm (0.4921") left the ends of the elongated hole untouched, but those portions would be filled by weld anyway.

Conveniently, I only would have to remove just a little from a 1/2" rod of Al to make a piece to press fit into the 12.5 mm hole. Unfortunately, just as I was starting to make this piece yesterday I hear a clink that sounded like a nut falling onto a piece of metal and drive was lost to the lathe's chuck. Two hours later I had diagnosed and fixed the problem, which was caused by the key somehow coming out of an almost-inaccessible pulley inside the almost-inaccessible, pitch-black cabinet on the hard concrete floor. Sigh…

Because my hands were now covered by some sort of grease that didn't want to wash off I didn't take any photos of the piece, so you'll have to visualize a ~1/2"-dia. piece of Al that was ~1/2" long, with tapers at both ends for the weld. I machined the Al piece 0.0005" oversize, pressed it into place in the housing with a vise, and then welded both ends using 4043 filler.

Today I mounted the housing on my mill, aligned it as described in post #540814, located the center of the nearby steel bush to within +/-0.0002", and then moved the table by X=0.930", Y=0.120". I mounted a 1/4" carbide spotting drill in a collet (rather than a less precise Jacobs chuck) to position the hole which I then opened up with a 3/8" drill, also mounted in a collet. Finally, I reamed the hole 7/16" as shown in the next photograph.

[Linked Image]

Because of the steps I took to position and drill this hole it should be correctly located to no worse than +/-0.001" (jumping ahead, with the stop in place in the hole it mates perfectly with the circular depression in the kickstarter quadrant).

The outer surface is faced for a ~0.65" OD washer. Unfortunately, at this point I discovered the design of the appropriate boring bar for my facing head interfered with the raised portion of the casting at the left of the hole. So I used a boring head that uses different dia. boring bars, manually advancing it a half-dozen times to produce the necessary recess, as shown in the next photograph.

[Linked Image]

The appearance of the now-repaired hole on the outer surface of the cover is shown in the next photograph.

[Linked Image]

And the appearance on the inner surface, to be compared with the first photograph in this post, is shown in the next photograph.

[Linked Image]

On the inner surface I milled away the projecting weld material to within ~0.002" of the surface of the casting and then used a pneumatic file to remove the rest. Although no one will see this surface once the gearbox is assembled, it's nice that the file left a linear texture to the surface that looks very much like that on the original casting.

Much earlier, in post #522315, I noted that the hole for the actuating arm in the outer cover was quite worn. However, unlike the present casting that is specific to the SCT2 (because 'SCT2' is stamped on it), the outer cover is common to other gearboxes. So, I'm going to take the lazy way out and swap the worn cover for one I have that is in good condition.

All that is left to do on this gearbox is to thoroughly clean the outer surfaces, press new bushes and bearings into place, and assemble it. The new bush for the sleeve gear will need to be reamed after pressing it into position, and some time will be spend with the polishing wheel on the outer cover. At that point the gearbox should be as good as new.
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 05/27/14 2:59 am


That is, as always a lovely job. You can not imagine how much I would like to have your machining skill's.

Regards
Rod
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/27/14 11:26 pm

Originally Posted by Redmoggy
That is, as always a lovely job. You can not imagine how much I would like to have your machining skill's.
Thanks very much for the compliment. However, if I didn't having machining skills to slow down progress I could have had this bike bolted together by now…
Posted By: BSAonAnyDay

Re: 1957 BSA Spitfire Scrambler - 05/28/14 12:25 am

I am awestruck by your attention to detail. Thank you very much for documenting this as you have. I admire your methodology and approach towards doing a restoration. Truly an inspiration. I will be following your progress and taking more notes to use as guidance for my future projects. Thanks again!
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/28/14 3:54 pm

Originally Posted by BSAonAnyDay
I admire your methodology and approach towards doing a restoration.
I definitely appreciate the compliment. My approach with this particular bike is the antithesis of what's seen on the many shows on cable TV. Shops slap things together, during which the lead character comments on the high level of skill, and at the end he declares that whatever they had been working on now to be in perfect condition.

Posted By: L.A.kevin

Re: 1957 BSA Spitfire Scrambler - 05/28/14 6:45 pm

Regarding your bearing journal repair, my company sends parts to be metal sprayed to this place:

http://www.surfacemodificationsystems.com/resources/gallery/

This place can supersonic cold spray or hot spray different alloys and grind to suit. Might be worth a try. They've done wonders for us. We've even sent radial compressor crankshafts to them.

Kevin
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/29/14 4:00 pm

Originally Posted by L.A.kevin
Regarding your bearing journal repair, my company sends parts to be metal sprayed to ...
Kevin,

Thanks very much for this suggestion. I've investigated all commercial variations of metal plating and metal spraying in considerable detail but, unfortunately, neither works for this application. Both types of techniques have lots of uses, but serving as the inner race of a needle bearing isn't one of them.

The only "additive" technique that I don't yet have enough information on to judge is welding using one of several alloys that have the required hardness. However, even though welding would work to provide the necessary surface it brings with it several problems.

The original shaft would have had at least two types of heat treatments after machining. One would have been to give the alloy the necessary strength so it wouldn't bend under the load, and the other would have been to provide surface hardening (e.g. "case hardening") to the area under the needle bearing. If I were to weld it I would then have to heat treat the shaft to restore the strength, and to do that I would have to identify the alloy used for the shaft in order to know how to heat treat it.

Although only a thin layer (~0.01") of hard facing would need to be applied by welding, the actual amount deposited would necessarily end up much thicker than that. Precision grinding would be needed to take it back down to the required diameter. Unfortunately, welding and heat treating would cause distortion, so the shaft would have to be straightened (to within a few thousandths) before it could be ground.

None of the above is impossible, but none of it is easy, either.

Again, thanks for the suggestion, but restoring the original shaft using a hardened sleeve still seems to be the only option for salvaging it.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/11/14 6:13 pm

Recent progress has been slower than usual thanks to some travel. But, I did make an important step forward today.

Earlier this spring someone in the UK sent me some interesting information about Gold Star oil tanks. Unfortunately, this information created a problem for my Spitfire restoration. For some years I've had a NOS oil tank in perfect condition ready to install. What I learned from the new information is the oil tank I've had all these years is incorrect for a 1957 Spitfire.

Sometime around the time my Spitfire was made BSA changed the shape of the outside surface of the oil tank and of the toolbox (which wasn't used on Spitfires) to a more rounded form. The difference in shape is fairly subtle, although quite obvious when the two types of tanks are side-by-side. However, for me, at least, if I'm looking at one of the "flat" tanks all by itself I'm only ~80% certain it's actually a flat one, not rounded. This is why I never could be certain of the shape by looking at the photographs in BSA advertisements.

Anyway, all I've had to go on until now is that the change happened in either the 1957 or 1958 season. Obviously, which of these seasons matters for this restoration. Thanks to the person in the UK I learned that Service Sheet 44 dated October 1957 states "In order to improve the oil flow the internal feed pipe and filter have been modified. The new oil tank is interchangeable providing it is used with the new filter assembly also." Although the shape of the tank changed it kept the same part number of 42-8367 that had been used since 1954. However, the filter part number changed from 42-8334 to 42-8426.

Unfortunately for me, having learned three months ago that the change didn't happen until the 1958 season meant I had to look for a different oil tank. Earlier today I made the swap. The new-to-me older tank has two very tiny dents in it but the metal is otherwise perfect condition. The dents will be easy enough to fill with braze. But, there's more to the story than this.

BSA's use of the word "filter" is interesting. Anything large enough to actually be stopped by the screen (chunks of metal, valve keepers, …) probably would have destroyed the engine already. But, more to the point, I had forgotten that the Service Sheet said the two tanks used different filters and, since the chrome on mine was perfect, I tried to switch them. The later-type filter went into the older tank a few turns but then got progressively tighter. Comparing the filters side-by-side the dimensions appear to be identical, so I made some measurements.

The OD of the 20 tpi threads on the earlier-style filter is 1.051" while on the later-style it is 1.064". Nominally, both are consistent with 1-1/16", but the 0.013" difference in OD certainly would account for the binding. Surely BSA didn't deliberately make threads with a non-standard diameter, so is it possible the earlier-style tanks all had been accidentally made with slightly out of specification tooling, with BSA taking the opportunity of the redesign to make proper threads?

The hole at the end of the filter for the oil pipe is 0.325" for the old-style and 0.375" for the new-style, consistent with a larger diameter internal feed pipe (note: it's non-trivial to measure the OD of a pipe recessed inside a tank, so I haven't tried to do this). The only visible difference is the older-style filters are made with steel screen while the later are brass. This alone would make it possible to distinguish old and new stock, which would seem to be essential. Have any of you with a large horde of pre-unit BSA parts (Boomer, Gordo, …) noticed this before? Is the steel/brass difference an actual difference that can be used to distinguish old and new types of filters? Everyone, drop whatever you're doing, pull those oil filters, and report back with the results of the OD and steel vs. brass.
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 06/12/14 2:18 am

To confuse matters further, my father had a completely original 59' flash. It had a flat oil tank and did tool box from the factory. They just fitted what they had.
Posted By: Per B - R.I.P.

Re: 1957 BSA Spitfire Scrambler - 06/12/14 4:00 am

To add to the confusion, in the literature for the B33 its stated that new rounded form of oil tank/toolbox was introduced in 1958 together with the alternator. The bigger toolbox was requiered to give space for the rectifier!
Posted By: Boomer

Re: 1957 BSA Spitfire Scrambler - 06/12/14 3:33 pm

When getting the BB Goldie ready for the rally I switched out the chrome oil tank for a stock original paint flat side tank. Both tanks were not correct for the model, should have a flip cap like the fuel tank for one, but fit the part. All the threaded oil filters I tried were exactly as you pointed out and the one that was in the chrome tank had a tear in it. I thought it was due to the dent that was right next to the fitting where the filter screwed in so I ended up using the filter with the tear that was in the chrome flat side oil tank.

So now, as you have pointed out, I would assume that all my spare oil filters were for the later tank.

BTW, I'm looking for one of the one year only BB swingarm oil tanks. Not only is the cap different but the shape is different. The tee fitting to secure it to the frame at the front edge of the tank
is different and the bracket it attaches to on the frame is welded on and not bolted on. I used the later set-up and had to use a spacer on the tee bolt and it pulls at an angle telling me the fitting on the tank is in a different place than the original tank also.


Sorry for digressing from the original point but I hope that helps.

Bill B...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/12/14 9:25 pm

Originally Posted by Allan Gill
my father had a completely original 59' flash. It had a flat oil tank and did tool box from the factory.
While anything is possible, not everything is equally probable. I tend to discount such anecdotes since there are a number of more plausible explanations, e.g. whoever sold the bike to your father told him it was original, and might have even believed that, but had forgotten he or an earlier owner had installed a replacement.

Originally Posted by Allan Gill
They just fitted what they had.
All the evidence I've seen over the years points to things not being quite as random or chaotic as that at the factory. In the same vein, the late John Gardner told me that although people commonly say that Gold Stars "were configured any way you wanted them" by the factory, nearly all machines where he could trace the actual history were supplied exactly as specified in the catalog.

Originally Posted by Per B
To add to the confusion, in the literature for the B33 its stated that new rounded form of oil tank/toolbox was introduced in 1958
Rather than adding, it subtracts from the confusion. A 1958 date is what is given in that Service Sheet I referred to in an earlier post, so your comment on the B33 is consistent with that. Thanks for mentioning this.

Originally Posted by Boomer
All the threaded oil filters I tried were exactly as you pointed out
Very interesting. Finding this out-of-spec difference in thread diameter for the earlier tanks is beginning to look like it might be a micro-discovery. I'll post more on this tomorrow, along with photographs and dimensions to easily allow distinguishing between the two versions of filters. Meanwhile, the next time you wander out to your workshop please look to see if the filters that you now think are the later ones have brass or steel screens.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/13/14 4:44 pm

At the left of the next photograph is the earlier-type filter used in 1954-1957 flat-sided oil tanks and on the right the later-type for rounded-side tanks introduced for the 1958 season. Both filters are the same 2-1/2" length from the sealing surface to the end so it would be difficult to distinguish between them by eye alone (unless we obtain more information showing that a steel mesh was always used on the earlier ones and brass on the later). However, an unknown filter easily can be identified using a 3/8" (or 9.5 mm) drill bit because it will fit in the hole at the end of the later-type filter but won't in the smaller hole of the earlier-type.

[Linked Image]

The next photograph shows the end of the earlier-type filter in greater detail (the later-type is the same, but with a slightly larger hole).

[Linked Image]

As discussed below the slightly smaller diameter of the threads on an earlier-type filter would allow it to be installed in a later-type tank if the hole in the end were enlarged so I imagine such modified filters are to be found. However, as can be seen, the inner surface of the ID is smoothly rolled over. This wouldn't be the case if examining an earlier-type filter that someone had modified to make fit a later tank by drilling it for the larger pipe.

As mentioned in a previous post, the OD of the 20 tpi threads on the earlier-type filter is 1.051" while on the later-type it is 1.064". Both are consistent with 1-1/16" (i.e. 1.063"), but the 0.013" difference in OD certainly would account for the binding when trying to use the later type of filter with an earlier tank if the threads in the tank also were made the same amount out of spec.

I keep an old edition of 'Machinery's Handbook' (15th, 1955) for information on obsolete threads since much of the relevant content on these fasteners was dropped from more recent editions. The 1-1/16" of this oil filter isn't a standard BSW, BSF or CEI fastener size, but the allowed tolerance for 1" and 1-1/8" BSW and BSF is +0"/-0.008". The difference of -0.013" I found for the earlier filter is well outside this. Also, the fact the later-style filter has the correct diameter lets it be used as a "plug gage" to test the threads on the old-style tank. The fact this "plug gage" binds in the hole says the threads in the tank also are out of spec.

Surely BSA didn't deliberately make threads with a non-standard diameter, so this seems to indicate the earlier-style tanks all had been accidentally made with tooling that was slightly out of specification. The fact the later filter is of the proper diameter and pitch but doesn't fit the earlier tanks indicates that for the four years that the earlier parts were made it was with tooling that was out of spec. by ~0.005". It appears BSA took the opportunity to correct this mistake when they introduced the new rounded tank with 1/16" larger internal pipes for the 1958 season. Still, this discrepancy is a bit puzzling since the threads in the tank would have been made with a tap so this means the taps BSA used were out of spec. But, no matter what, somewhere some company's quality control department didn't do their job properly.

A few other measurements: the internal pipe in the oil tank is recessed by 1-3/4" which makes it difficult to accurately measure its OD. This is shown in the next photograph.

[Linked Image]

(note: the residual oil isn't defying gravity; the tank was at an angle on the table and I rotated the photograph to give it the proper orientation). Although I could bore a series of holes in the ends of Al rods to make female plug gauges to determine the OD fairly accurately, there is no need for such accuracy. Instead, using drill bits to judge the approximate OD of the pipe in the old-style tank shows it is ~5/16" (~0.313"). The ID of the end of the old-type filter is ~0.328" so the annular clearance is ~0.008". The OD of the pipe in the rounded tank is ~3/8", and the ID of the new-type filter for that tank is ~0.377", so again the annular clearance is a few thousandth of an inch.
Posted By: BritTwit

Re: 1957 BSA Spitfire Scrambler - 06/15/14 12:05 pm

Thanks MM
After a lengthy discussion on the oil tank filter issue, I have now convinced my wife that I am indeed crazy.
A previous post mentioned "Service Sheet Number 44". I have a poor copy of a "BSA Parts Service Bulletin"(unable to read the date). It also mentions #44. I don't have a working scanner, or I would post it. It states the following:

When requesting replacement Oil Tank Filters, it is important that they are ordered as follows:-

For machines prior to the following Frame Numbers:-

A Group Frame Number EA7-12641
B Group Frame Number EB31-8252
Gold Star Frame number CB32-6667
Use Filter assembly Part Number 42-8334

After the above frame numbers use Filter assembly Part Number 42-8426

The latest type Oil Tank part number 42-8367, can be used as a replacement on all Models provided that the new Filter assembly Number 42-8426 is also used.

Service Sheet Number 44 also refers to this change.

C/R.A.B. BSA Motor Cycles Limited, Service Dept., Birmingham, 11.


Perhaps you could use your dispatch date and cross check the dispatch date on EA7-12641


Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/16/14 1:28 am

l
Originally Posted by Magnetoman
Originally Posted by Allan Gill
my father had a completely original 59' flash. It had a flat oil tank and did tool box from the factory.
While anything is possible, not everything is equally probable. I tend to discount such anecdotes since there are a number of more plausible explanations, e.g. whoever sold the bike to your father told him it was original, and might have even believed that, but had forgotten he or an earlier owner had installed a replacement.
Originally Posted by Allan Gill
They just fitted what they had.
All the evidence I've seen over the years points to things not being quite as random or chaotic as that at the factory. In the same vein, the late John Gardner told me that although people commonly say that Gold Stars "were configured any way you wanted them" by the factory, nearly all machines where he could trace the actual history were supplied exactly as specified in the catalog.
Further on this, an undated two-page Hap Alzina information sheet states in all CAPS that:

"EACH BSA MOTORCYCLE HAS CERTAIN STANDARD SPECIFICATIONS AS BROUGHT INTO THE UNITED STATES AND THESE AND NO OTHER ARE THE SPECIFICATIONS AT TIME OF SALE."

It goes on to give as an example that:

"What this means, in effect, is that a Catalina Scrambler is a Catalina Scrambler… The Clubman engine is not available in the Catalina frame … a Catalina is not available with the Clubman carburetor and Clubman cams, etc."

Another undated two-page Azina bulletin deals with "Subject: Special B.S.A. Motorcycle Orders." Again, in all CAPS it emphasizes that:

"GENERALLY SPEAKING - SPECIAL ORDERS ARE NOT POSSIBLE OF ACCEPTANCE OR FULFILLMENT"

It goes on to say that although orders for Gold Stars with any of the various specific allowable factory options "...can, in a technical sense, be accepted by the Works...", it immediately cautions in all CAPS that:

"SUCH ORDERS ARE APPROXIMATELY FIVE TO SIX MONTHS DELIVERY FROM THE DATE OF ORDER PLACEMENT AND ARE FIRM, NON-CANCELABLE ORDERS FOR THE DEALER'S ACCOUNT THAT MUST BE ACCEPTED BY THE DEALER ON ARRIVAL."

The bulletin advises the dealer to try to "...reshape the customer's desires to some form of readily available equipment." Failing that, the dealer should get a very large deposit because the dealer will be charged in full for the special-order bike once it does arrive. This Alzina bulletin confirms that while in principle Gold Stars could be ordered with a wide variety of optional equipment, at least in the U.S., bikes that deviated from the standard catalog specification would have been unusual.

The bulletin also advises the dealer to agree to make any changes the customer wants to any bike in his shop, at the customer's expense, since "This gives you a brand-new, saleable item on your shelf free of cost…" It doesn't take much imagination to realize how such parts swaps could result in bikes leaving dealers' shops with new, but incorrect items previously taken from other bikes, and for buyers to incorrectly think that is how their brand-new bike came from the factory.

Originally Posted by BritTwit
After a lengthy discussion on the oil tank filter issue, I have now convinced my wife that I am indeed crazy.
All I can say is, my wife is several decades ahead of your wife. However, you're probably not giving your wife nearly enough credit for having realized this about you long ago.

Originally Posted by BritTwit
I have a poor copy of a "BSA Parts Service Bulletin"(unable to read the date).
Perhaps you could use your dispatch date and cross check the dispatch date on EA7-12641
That would be Bulletin No. G.5 dated June 1958. Unfortunately, I only have A10 records for 1957 Spitfires and those frames are all in the CA7A-xxxx range. However, the high EA7 number indicates the switch on A10s came sometime into the 1957 model year. The same for the Gold Star and the B-group numbers.

I should say that, all by itself, Bulletin G.5 doesn't determine what oil tank should be on a 1957 Spitfire. The wording says a new filter had been introduced as of the June 1958 date, and it also says the latest type of tank uses that filter, but it doesn't actually address how many different tank(s)/filter(s) might have been used in previous years. However, the wording is consistent with what the other information says, i.e. that my Spitfire uses the flat oil tank.
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 06/16/14 2:25 am

Just been looking back through this thread at the photos you posted, some catalogue images are hard to tell, the the cutout of the super rocket next to the scrambler seems spar any that they are both flat sided tanks - the curve on the oil tank seems too sharp to be the rounded type.

Do you have anymore images?

Enjoying your progress :bigt
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/17/14 4:11 pm

Originally Posted by Allan Gill
Do you have anymore images?
Enjoying your progress
Thanks for your comment. I've posted every image of this machine that I've found in 20 years of searching. But, since I intend for this thread to be the most comprehensive collection of information possible, you can count on me to post anything new that might turn up in the future.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/22/14 11:16 pm

As soon as I received the SCT2 gearbox three years ago I ordered all the bearings and bushings for an RRT2 so they would be on hand when I was ready to being work. However, when I started on the gearbox in earnest a few months ago I looked at the parts and wasn't happy with everything I found. For example, the bearing for the sleeve gear should have crowded rollers for heavy loads but the Japanese-made one that was supplied is for high speed operation, with only half the number of rollers and a plastic cage. These are shown in the next photograph, with the Japanese bearing at the left and a proper Torrington bearing on the right

[Linked Image]

The not-quite-right bearings came from a supplier in England (not Autocycle). But, thanks to eBay, I now have several lifetime's worth of the proper NOS gearbox needle and ball bearings. By the way, note the presence of the oil hole in the housing. As normally supplied by Torrington there is no oil hole and whether or not it is present the number stamped on a Torrington bearing itself does not have an "-OH" suffix. The catalog states that only on the box containing the bearing will "-OH" be printed to denote that the contents have the oil hole option.

As mentioned in an earlier post, the mainshaft supplied by Autocycle meets all of the specifications except for the roughness of the shaft immediately under the needle bearing which does not meet modern standards. I measured an average roughness (Ra) of 15-16 micro-inches whereas modern standards call for a maximum of 8 micro-inches. I should say that a c1970 Torrington catalog lists the maximum roughness as 16 micro-inches so the shaft actually does meet those older requirements.

Without going into too much detail, the way roughness values are defined the maximum peak-to-valley roughness Rz will be quite a bit greater than the average roughness Ra. In my case Rz = ~130 micro-inches (~3.5 microns) while Ra = 15 micro-inches (~0.5 microns). To knock down those peaks, which also will reduce Ra, requires polishing with an abrasive of size somewhat smaller than Rz. I decided to start with 1 micron grit and to go to 0.5 micron after that if necessary (note: most people consider Simichrome to be a fine polishing compound but it is 8-10 microns). I hope mixing the inch/metric units doesn't cause confusion for anyone.

I polished for 30 seconds with the 1 micron abrasive and measured the roughness to see what progress I had made. The principle being, I'd rather find out as early as possible if metal was being removed faster than expected. However, the change in roughness, if any, was small, so I polished for another 2-3 minutes, measured again, and found Ra = 8 micro-inches (Rz = ~50 micro-inches). The result is shown in the next photograph, with the polished region for the needle bearing quite apparent:

[Linked Image]

Since at this point polishing had reduced Rz from its original ~3.5 micron value to about that of the 1 micron grit size further progress would require changing to a finer grit abrasive. However, since Ra now met the 8 micro-inch specification given in modern catalogs, I was done.
Posted By: Peter R

Re: 1957 BSA Spitfire Scrambler - 06/23/14 4:20 am

MM, this is intesting info for me, the bearings in the gearbox of my goldie are similar to the japanese bearings as shown on the left in your pic.

According to my bearing supplier, Torrington is no longer in business, and he was unable to supply the correct needle bearing with the large nuber of needles.

Should I be worried ? so far the 'íncorrect' type ofbearing gave no problems, athough i have not done many miles with it yet.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 06/23/14 5:17 am

Quote
Torrington is no longer in business



Torrington is no longer independent as its owned by Timken but its still around. I would stay away from people spouting such rubbish.
Posted By: John Healy

Re: 1957 BSA Spitfire Scrambler - 06/23/14 9:55 am

http://www.timken.com/en-us/about/NewsRoom/Stories/Pages/TimkenSellNRBBusinesstoJTEKT.aspx

In 2009 Timken sold the needle bearing business to a holding company that sells needle bearings under the Koyo-Torrington brand name. We are still able to get made in USA Koyo-Torrington needle bearings.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/23/14 11:35 pm

Originally Posted by Peter R
the bearings in the gearbox of my goldie are similar to the japanese bearings as shown on the left in your pic. ... Should I be worried ?
I won't tell you to be worried. But, I also can't tell you otherwise. The problem is I can't think of any way to model the side thrust the bearing will be subjected to. The type of bearing you have has half the rollers so the pressure on them, the race, and the shaft is twice that of a crowded roller bearing. We know that a crowded roller can withstand the side thrust without exceeding the yield strength of any of the components. But, perhaps it is overspecified by a factor of 4x, in which case the type of bearing you have is still 2x stronger than it needs to be. In which case, you're fine. But, a crowded bearing race might be overspecified by 50%, in which case you will have problems in the future.

Another issue is quality. Torrington bearings are a known quantity. Further, they are made to published specifications that require being pressed into housings of prescribed diameter to compress the race just the right amount to give the required clearance with the shaft. Think about all the discussions of C2 vs. C3 etc. ball bearings to be used on engines. Although all these have nominally the same OD and ID, one clearance will result in a noisy engine while another might cause it to seize. What about the unknown Japanese bearing? Even if made to strict metallurgical standards, without knowing what the dimensional tolerances are there's no way to meet them.

So, sorry, I can't tell you not to be worried.
Posted By: Peter R

Re: 1957 BSA Spitfire Scrambler - 06/24/14 3:24 am

OK, thanks for the reply, I will replace the bearings in the not too distant future, for the sake of piece of mind if nothing else..
I will contact Autocycle to ask if they can supply the correct bearings.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 06/24/14 5:11 am

There are other considerations on needle bearing life other than crowded vs caged having different numbers of rollers. A caged needle roller will perform better at high speeds than a crowded bearing as the cage keeps the rollers from rubbing against each other. So low speed high load is best handled by crowded, low load high speed is handled best by a caged roller.

As for the c1, c2 equivalent ie the ISO/DIN std on ball and roller bearings there are a few for needle rollers too.


http://www.iso.org/iso/home/store/catalogue_tc/catalogue_tc_browse.htm?commid=45572
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/24/14 9:49 pm

I should have mentioned the Torrington part numbers in an earlier post. The reason I ordered the bearings from a motorcycle parts supplier in the first place is I hadn't taken the gearbox apart yet at that time so I didn't know what bearing was required for the SCT2/RRT2 sleeve gear. Now I do. Anyway, the required Torrington bearings (with dimensions, in case you need to locate an alternative manufacturer) are:

Sleeve gear (only used on the SCT2 and RRT2)
B-1314-OH
13/16" ID, 1-1/16" OD, 7/8" wide

Inner cover (used on both 'T' and 'T2' gearboxes)
B-1212-OH
3/4" ID, 1" OD, 3/4" wide

The bearing needed for the main gearbox housing depends on whether or not a separate, slightly convex, 'cap' is pressed in at the outer end of the hole in the housing to seal the oil in. If the housing has such a cap, then an open ended bearing is used. If not, than one with a closed end is required.

Main gearbox housing (used on both 'T' and 'T2' gearboxes)
B-1112-OH (open ended)
or
M-11121-OH (closed end; note, the extra '1' at the end of the no. isn't a typo)
both are 11/16" ID, 7/8" OD, 3/4" wide
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/25/14 4:12 pm

Originally Posted by Peter R
so far the 'íncorrect' type ofbearing gave no problems, athough i have not done many miles with it yet.
Looking at the photo in my post of 6/22 the Japanese bearing has ~16 rollers in it and the Torrington ~32. Using those numbers in a formula in my c1970 Torrington catalog, the Basic Dynamic Capacity (BDC) of the Japanese bearing will be 63% of that of the Torrington if it is of the same quality and used under identical operating conditions. So, cutting the number of rollers in half significantly reduces the load capacity of the bearing although doesn't quite cut it in half. This means that as long as the crowded roller bearing that BSA used was overspecified by a factor of ~2x you wouldn't have to worry your caged bearing would fail under the load. Of course, we don't know if that 2x safety factor was built in, so you do have to worry about this.

Since you already need to worry, to give you a second thing to worry about, another effect of a reduced number of rollers is a reduction in the lifetime of the bearing. Using another formula in the catalog, reducing the BDC to 63% reduces the lifetime to 21% for an identical load. To put this in practical terms, if the Torrington bearing that BSA used for this purpose would have lasted, say, 20,000 miles before needing replacing, a caged bearing of the same quality would have lasted only ~4,300 miles.

There are so many unknowns involved (e.g. was a gearbox run low on oil for some number of miles?; was incorrect weight oil used?; was the oil never changed?; did the previous owner repeatedly shock-load the layshaft by downshifting without using the clutch?; etc.) that I doubt if there is any data on the expected lifetime of the needle bearings on the layshaft of a BSA gearbox. But, I'll go out on a limb and speculate that in the ways our gearboxes are commonly (mis)used, 20,000 miles is a reasonable lifetime to hope for from an original bearing. If this is the case, (mis)used in the same way a caged bearing of the same quality is only going to last 4,300 miles. But, irrespective of whether or not 20,000 miles is a reasonable expectation from a high quality, crowded roller bearing in this application, you won't get any more than ~20% of the mileage from any caged roller bearing. And less -- perhaps far less -- from a caged roller bearing of unknown quality.

Posted By: Peter R

Re: 1957 BSA Spitfire Scrambler - 06/25/14 5:52 pm

MM, thanks very much for your reply, your input is greatly appreciated.
I understand that the integrity of the gearbox will be seriously impaired with the bearings that I am currently using, and will certainly exchange them for the correct "crowded" needle bearings before something goes seriously wrong.
Thanks also for providing the correct part nrs in your posting above.


Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/27/14 1:26 am

Originally Posted by Peter R
I understand that the integrity of the gearbox will be seriously impaired with the bearings that I am currently using, ...
I can't say I've done a comprehensive survey of all suppliers, but it appears the incorrect type of bearing is commonly sold. However, given the calculations outlined in my previous post, they still should last long enough that most owners won't realize it was the fault of the supplier, not of their treatment of the gearbox, that resulted in failure after relatively few miles.
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 06/27/14 2:41 pm

I concour with the incorrect parts being shipped. I used to build a few bantam engines at one time ( amongst others ) and very often the caged roller would be sent out for use at the little end - I refused to use them and since only bought little end bearings which I could see before I bought, and these weren't Britbike suppliers I was buying them from! ( well the incorrect bearings DID come from BB suppliers)
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/10/14 2:14 am

I only managed to make small progress since my last post due to a trip to Turkey. But, thanks to what felt like countless hours in transit I did get one thing done that I will need when it comes time to fabricate the exhaust pipes. The extra-long pipes are special to the Spitfire and none have turned up in 20 years of searching so I'll have to weld my own. To do that requires knowing their length and geometry which the following photograph shows.

[Linked Image]

As soon as I measure the length from the swinging arm pivot to the shock mount the length and amount of bend will be determined by the information on the photograph. I have three pairs of A10 pipes to work with (all with dents, scrapes and rust) so I should have more than enough raw material to work with. However, I'll complete work on the gearbox before doing anything else.
Posted By: Graybeard

Re: 1957 BSA Spitfire Scrambler - 07/10/14 5:55 pm

Wow, this thread is absolutely fascinating! Thanks.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/11/14 8:32 pm

Originally Posted by Graybeard
Wow, this thread is absolutely fascinating! Thanks.
Thanks very much for the compliment. As I mentioned in the first post of this thread, my approach to restoring this BSA isn't one everyone might want to copy. It's somewhat different than the level of detail found in a Haynes manual…

Clearly, I have a lot left to do. But, the existence of this thread is a nice motivating factor that keeps me slogging along despite having plenty of reasons to let the project gather dust.

Cosmetics (paint, welding holes in mudguards, removing dents and polishing alloy pieces, etc.) will take quite a bit of time but after the gearbox is back together, the "only" major components left to deal with are the engine, magneto, and forks. Because of the irritating nonsense from one particular person that I had to waste time responding to when writing my Bosch ZEV restoration thread (thankfully, the worst of which was deleted by the moderator), I'll decide when I come to it whether to post the details of restoring its K2F magneto. However, with that possible exception, my plan is to describe everything else.

There's no danger this restoration will be finished anytime soon, so stay tuned…
Posted By: joe a.

Re: 1957 BSA Spitfire Scrambler - 07/21/14 11:29 pm

rotopeen flaps do a nice job of texturing plus the primary added benefit..
[email protected]
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 07/23/14 12:44 pm

Originally Posted by joe a.
rotopeen flaps do a nice job of texturing
Thanks for the suggestion, although after examining how they are made I'm fairly skeptical they would restore anything like an authentic sand-cast texture. Unfortunately, they are surprisingly expensive (~$60 ea., but only available in boxes of 10 from Grainger) making it difficult to buy a few in different grades to try out on a scrap piece.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/14/14 10:11 pm

The September issue of 'The Classic Motorcycle' was waiting for me when I got home tonight, containing the first article on Rocket Gold Stars I've seen since I started my restoration thread a year ago. Interestingly, this is the first article I've seen thus far that mentions that 1957 Spitfire Scramblers "have some claim to be 'the first Rocket Gold Stars'." It's especially interesting to me since that's essentially the title of the first post of this restoration thread. Further, it's the first article that says that perhaps "the RGS wasn't just dreamed up by Eddie Dow..." Hmm, that's another point I made in this thread that I've not seen anywhere else before. I detailed how the dispatch records I possess show the first Spitfire was shipped in February and the last in September. The article is unusually detailed in giving the specific date range: "Feb-Sept 1957 was the export only A10 Spitfire Scrambler (SS)."

Beyond the above, the article also details various obscure bits of technical information about the 1957 Spitfire that, again, are in this thread but that I've not seen in any article or book before this. However, one odd disconnect is the article says "some 350 1957 Spitfire Scramblers were built," while I detailed in this thread that the number was 424. Well, I did write that "364...went to the west coast" which quick skimming and rounding could end up as 350.

That said, there is no acknowledgement in the article that the information came from elsewhere which must mean the author independently came across it all himself... However, it is pleasing that -- finally -- information on these 1957 "Rocket Gold Stars" is coming to wider attention.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 08/15/14 3:17 pm

The September issue of 'The Classic Motorcycle'
is this a us mag
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/15/14 4:20 pm

Originally Posted by paul67
The September issue of 'The Classic Motorcycle'
is this a us mag
No, definitely English. It has been around since the early 1980s, was for quite a while a sister publication of 'Classic Bike', but sold to another publisher a decade ago when EMAP was going through some turmoil. However, people in the UK would have received their copies of this issue a week or two ago.
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 08/16/14 5:30 pm

Hi All,
Quote
That said, there is no acknowledgement in the article that the information came from elsewhere which must mean the author independently came across it all himself


Somehow I doubt this very much, They are not prone to listing acknowledgements !!!
I wonder did the writers research bring him here ?

There are a few contradictions as well ???
One being that RGS models used "Gold Star frames" (item 4 page 29) and then later on saying that RGS's were the only models to use an "A10" frame prefix
The article states that the 1957 Spitfire Scrambler frames were
"gold star Catalina!" and "complete with the telltale kink in the right bottom frame rail" (P28)

Magnetomans photos show a "straight " bottom rail

I coulld go on

Cynical??
John
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/16/14 7:39 pm

Originally Posted by chaterlea25
I wonder did the writers research bring him here ?
"Research"? We don't need no stinkin' "research."

Magazine writers get paid by the word. If it takes them twice as long to write those words because they spend time doing research, their hourly pay is reduced by half. The combination of significant detail (e.g. "Alzina had also introduced the stronger S&W valve springs...") with glaring errors (e.g. "complete with the telltale kink in the right bottom frame rail...") has all the hallmarks of a modern student's term paper. That is, one hastily written the night before it's due by cut/pasting "research" googled from the internet and reworded to avoid a failing grade for plagiarism.

Even when there aren't errors in the internet content, the hasty rewording process can be counted on to introduce them since time spent proof-reading also is time wasted. In this way the "a Gold Star Catalina-style scrambler frame without passenger footpeg loops" that I wrote easily can become "a Gold Star Catalina frame, without frame loops to carry passenger footrests..." when reworded. With the rewording having left "Catalina," rather than "Catalina-style" now on the screen in front of him, with no extra effort at all the writer can add to the word count by completing the sentence with common knowledge "...and complete with the telltale kink in the right bottom frame rail to accommodate the single's oil pump." Whether or not this is what happened, it's exactly the sentence that is in the magazine article.

It's hard to decide which is more upsetting. Not to have been acknowledged for 20 years of effort accumulating information I've never seen before in any book or magazine article and presenting it here so others can benefit from it. Or, to read a bastardized form of misinformation. If someone is going to copy, at least they should show the courtesy to copy correctly...
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 08/17/14 4:48 am

Right on MM, I knew the article as soon as I read the post and thought what a load of crap. Everytime there is an A65 article it too is littered with hog wash and rediculas mistakes

"And a reversed cam plate in close ratio gearbox to give the racers a preferred, one up three down gearshift pattern" - no mr writer, that was achieved by the rotating of the gear lever.

It's at those points where I stop reading the article and use the photos for refrence instead.
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 08/17/14 5:54 pm

Hi All

Quote
Or, to read a bastardized form of misinformation


I could not have put it better

John
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/20/14 1:23 am

Originally Posted by chaterlea25
I could not have put it better
As an update, I was sufficiently bothered by this that I wrote to the author on Sunday. He responded this morning with a sincere apology that he cc'd to the editor and said a brief letter to correct this would be in an upcoming issue. Apology accepted, so back to motorcycles.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/29/14 4:12 pm

Anyone following this thread might have detected a slowdown in activity. In fact, the restoration hit a brick wall in the middle of July in the form of a new house. The following six weeks all my time in the old garage was spent getting things boxed and as organized as possible for the upcoming move. This was followed by a two-week delay after we took possession in order for my new garage/shop to be upgraded with all the electrical outlets, A/C, air lines, and lighting I ever could want (when all the lights are switched it's 1100 lux, which is the level of a surgical operating room). A motorcycle-friend who owns a construction company was the general contractor and he did a fantastic job in terms of minimum time and maximum quality. Only this weekend did I manage to get the lathe and mill, the two heaviest, least-mobile pieces and thus the last items, moved to their new home. With those items having been successfully transferred I feel a, ahem, huge weight has been lifted.

Although both the garage and library have 2x more floor space than I used to have, with 2x more shelving area as well, everything seems to have expanded by at least 3x in the move, resulting in temporary gridlock. To arrange anything first requires moving three other things, one of which is the original thing I need to move. As a result it probably will be a few more weeks before I'm able to start doing much actual work in the garage. However, I had made notes over the years of how I would like an ideal shop to be configured (e.g. air lines with quick connects every 10 ft.), and now I have it. In the years ahead this should make up for the pain of this move.

One positive aspect of the move was "discovering" more than a few interesting items I had forgotten I owned. One negative aspect is no longer remembering what bikes some fairly large parts go with. I probably will be posting a few "what are these wheel/hub/forks?" photo queries in the future.

Meanwhile, although over the past month I've developed aches in places I didn't know there were muscles, I'm pleased at the same time my magneto restoration thread passed the 50k views mark. Also, my friend used this magneto, without any maintenance to it since I restored it two years ago, for another 3000+ miles in this year's Cannonball Run, so it now has covered ~5000 miles without problem. This is consistent with my contention that there is no excuse for a properly rebuilt magneto to fail. And yet, "professionally rebuilt" ones continue to fail with remarkable regularity... (I know of at least four that failed in this year's Cannonball, which is a pretty high percentage since by far most of the 101 entries were of newer vintage American machines that did not use magnetos). But, I digress.

As things slowly return to normal, my goal is to make enough progress on the Spitfire restoration to have something new to post about it within a month. First, though, I have to rearrange enough boxes to find the Spitfire…
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/22/14 6:34 pm

Originally Posted by Magnetoman
First, though, I have to rearrange enough boxes to find the Spitfire…
OK, I found the Spitfire. But, while I have my new garage back into somewhat functional shape at this point, three months after I started packing up in the old one, I left reassembling the lathe until the end. I had to break the lathe down into a few major pieces for the move, and then put it back together, all of which required crawling around in uncomfortable positions on the concrete floor. However, the most time consuming part of the task is re-leveling the lathe. If the ways aren't perfectly parallel with each other all lathes will cut a taper, and the best way to make the ways parallel is to level a lathe to a high degree of accuracy.

I started out with a carpenter's level and then moved to a Starrett Machinist's Level having sensitivity of 0.005"/ft. Only after doing as well as possible with it can the final Master Precision Level (0.0005"/ft) be used. It's so sensitive that the lathe has to be essentially level to begin with or the bubble will be pegged at one side or the other with no hope of using it to do better. Barely moving the leveling bolts on the lathe, and/or tightening the hold-down bolts, causes the bubble to move so it's really fiddly to get the lathe perfect. Complicating the process, if a piece of grit only ~0.0002" is under the level it makes a perceptible difference.

[Linked Image]

In contrast to lathes, mills don't have to be level to do their job. However, if they are level it can make fixturing some objects to the table easier so I also leveled the mill. Actually, I leveled both a week ago, gave them the following week to accommodate themselves to their slightly new shapes, then did the final leveling (which has to be checked periodically).

With this final major task of the move out of the way I now can slowly start work on motorcycles again. However, a lot of reorganization remains to be done before I'll have full functionality of the garage so I'll be dividing my time between getting things in order and doing actual work. So, although I'm (finally) starting to make progress on the Spitfire again, I'm still getting back up to speed.
Posted By: Vespa

Re: 1957 BSA Spitfire Scrambler - 10/25/14 11:07 am

Originally Posted by Magnetoman
Because of the irritating nonsense from one particular person that I had to waste time responding to when writing my Bosch ZEV restoration thread (thankfully, the worst of which was deleted by the moderator), I'll decide when I come to it whether to post the details of restoring its K2F magneto.


Hi Magnetoman,

I have created an account just so I could post this reply.

Please don't let one person deter you from posting any details from your project.

There must be many, many lurkers like me who read this excellent thread of a very important and interesting restoration and who very much appreciate your sharing.

Kind regards,

An avid fan.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/26/14 3:59 pm

Originally Posted by Vespa
I have created an account just so I could post this reply.
Thanks very much for your nice comments and encouragement. It's very nice whenever I hear that the extra effort it takes to document this restoration is appreciated.

It's been frustrating not having a functional workshop for the past three months (it seems like it should only take a day to pack, a day to move, and a day to unpack, but …), but as I get fully back up to speed my new, larger, better facilities will make it easier and more pleasant to continue on this restoration. So, stay tuned because there's much more to come.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/11/14 10:06 pm

There are a million stories in Restoration City. This is one of them.

I don't have things quite ready to return to the gearbox just yet so I took on a smaller project to build momentum. As I wrote in an earlier post, after having looked for the proper 376/89 carburetor for 15 years, I finally found one last year. Since it needs to be restored I decided now was as good a time as any to do that.

Repeating something from July 2013, in separate publications Amal and Hap Alzina give different specifications for the jetting:

_____________Amal____Alzina
Main jet_______400_____240
Needle position__4_______3
Cutaway______3-1/2_____4

Of course, there's no reason to expect the carburetor I bought has the same jets as it had when it left the factory 57 years ago but, for what it's worth, it has a 330 main jet, the needle was on the 3rd groove, the slide has a 3-1/2 cutaway, and the pilot is 30. Further, despite the corrosion on the outside of the needle jet, its ID is within specs at 0.1062"

The slide was a tight fit in the bore and clearly either it, the carburetor, or both were somewhat oval. Still I was able to find an orientation that allowed me to push it out with my fingers. However, the jet block didn't want to come out with gentle persuasion so I let it sit with Sili-Kroil for a few hours then knocked it out with a few taps of a light hammer on an aluminum rod held against the jet block. As can be seen from the next photograph corrosion is evident on the smaller diameter portion at the right (as well as on the needle jet), which is what was holding it in place.

[Linked Image]
Despite several spots of corrosion like the above the carburetor is in very good condition.

To check for warping of the flange I mounted the body on a V-block that I placed on a surface plate. This particular "toolroom grade" plate simply sits on a workbench so it isn't perfectly level (which isn't an issue for most uses). As shown in the next photograph, to get things close I rotated the carburetor in the V-block until it had the same 0.3 degree reading as the plate itself, i.e. so on average the face of the flange was parallel to the surface plate.

[Linked Image]

I then adjusted the dial test indicator to read '0' at what I (correctly) assumed would be the lowest point on a bowed flange, i.e. half-way between the mounting holes. As the next photograph shows the indicator made one full revolution, 0.030", when moved to either mounting hole. This is the amount of warping that needs to be removed.

[Linked Image]

I next used a Mitutoyo bore gage to check for out-of-roundness of the bore for the slide, and a 1"-2" micrometer to measure the slide. I measured the carburetor at the very top, just above the inlet track, and just below the inlet track, and with the gage oriented parallel and perpendicular to the inlet track. I measured the slide at the very top, in the middle, and just above the cutaway, also parallel and perpendicular to the direction of the inlet track. The result is too much data to type so I'll summarize the important points.

Carburetor body:
The maximum difference between the bore parallel and perpendicular to the inlet track was at the very top where the difference was 0.008". Just above the inlet track it was 0.003" and just below 0.001". Given the very small amount of distortion below the inlet track I infer the original specification was a bore of 1.310".

(note: as a result of more careful measurements made later in this thread I believe the original bore was a few thou. larger than I wrote above, i.e. it was 1.3125" (1-5/16"). This makes sense because it is consistent with standard tooling having been used to make the bore, with the slide then ground slightly undersize to provide the desired 0.004" clearance. It's less expensive to make bores of just about anything -- carburetors, engine bushes, etc. -- standard sizes and then turn the mating part undersize to provide the necessary clearance, than vice versa).

Slide:
The maximum difference was at the bottom where it was 0.013".

I then clamped the slide in a fixture I had made some time ago by boring a 1.308"-dia. hole in a 2"-dia. Al rod 2" long and then slitting it. After this treatment I found the difference at the bottom had been reduced to 0.004".

[Linked Image]

I then used the fixture in the next photograph on the body:

[Linked Image]

The Al rod has an OD of 1.308" which gave it a slight clearance fit in the distorted body. The 1/2" bolt pulls the carburetor against the 1/4" steel plate forcing the mounting flange back into shape, which at the same time reduces the distortion of the bore. To compensate for springiness of the metal I used 0.021" washers between the carburetor's "ears" and the steel plate.

After clamping this assembly using a fair amount of force (i.e. an Allen socket torqued with a 3/8" breaker bar) I found the flange to be flat on the surface plate with no sign of rocking in any direction. This means the initial ~0.030" warping has been reduced to no more than a few thousandths. Also, the maximum out-of-round of the bore had been reduced from 0.003" to 0.001". Mentally averaging the various measurements the ID of the bore in the region important to the slide is now ~1.315" and the OD of the slide is ~1.303" so the clearance is ~0.012" (i.e. the components are a bit worn). Whereas the slide was a tight fit before it now fits freely in the bore.

I still have to reassemble the carburetor before this job is finished but that shouldn't take long.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 11/12/14 9:59 am

I kinda like the look of those carb-fixing tools!
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/13/14 11:35 pm

Originally Posted by GrandPaul
I kinda like the look of those carb-fixing tools!
Thanks. I should have said a few more things in my post about removing the distortion from the carburetor body.

After my first firm clamping of the body in the fixture there still remained some small amount of bowing due to springiness of the metal. I then put the two thin washers in place and clamped it down again, but not hard enough to make the bowed part actually touch the steel plate. When I backed the pressure off I saw from the even gap between the flange and the steel plate (of thickness equal to that of the washers) that I had been lucky in my guess of how much "overcorrection" was needed because the gap appeared to be uniform across, i.e. the flange appeared to be flat. It was quick enough to remove the carburetor from the fixture and confirm using the surface plate that the face of the flange indeed was flat. However, had there still been some remaining bowing I would have repeated, but with a little additional force.

The current clearance for the slide is ~3x what it should be, which is part of the reason I haven't reassembled the carburetor yet. The slide shows obvious signs of wear so I'm first going to go through my horde of parts to see if I have one to replace it with. Failing that, buying a replacement slide and hoping it is at least a few thou. larger is Plan B. Plan C might be for me to true up the bore and fit a sleeve to the slide. But, given the rarity of the carburetor I'll have to decide between living with the wear, or subjecting it to reconstructive surgery. However, the main reason I haven't reassembled it yet is that I want to search my stock for fittings that might be newer-looking than the ones that came with this carburetor.

By the way, the large steel plate in my previous post was a work in progress. I didn't happen to have an appropriate piece of steel handy when I first made this fixture several years ago so I made the plate from aluminum. I took the opportunity of working on this carburetor to make a new plate from steel but only had drilled a 17/32" hole through it when I took the photograph (although I had used it in the form shown to fix the carburetor). The next photograph shows the completed plate, cut down to size and with 5/16" holes (actually, using an 'O' drill bit to provide some clearance) to take care of any possible "reverse bowing" of the flange.

[Linked Image]

The next photograph is of the portion of the assembly that fits in the bore, in which it is more obvious there is a 3/4" slot machined in the back side to avoid having to use a separate socket to hold the nut while tightening the cap screw.

[Linked Image]

Finally, I realized I hadn't shown earlier in this thread how I make the all-important measurement of the actual ID of needle jets (as opposed to the not-always-correct size stamped on new ones). I have two types of bore micrometers I use for this, but the one I used to measure the needle jet in this particular carburetor is shown in the next photograph:

[Linked Image]

A discussion of both types of bore micrometers can be found in a thread starting at:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=519624#Post519624
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/23/14 2:32 am

Unfortunately, the ~0.012" clearance of the slide in the carburetor body is just too much to live with so I have no choice but to deal with it. While "everyone" sleeves the slide in the case of a worn carburetor, it's clear to me that sleeving the body is the right way to do it. The right way, but also the hard way. Unfortunately for me, the reason I say this will become clear in upcoming posts. Anyway, on its way from McMaster-Carr is 1 ft. of a machinable grade of brass tubing (i.e. 330) with 1-3/8" OD, 1-1/8" ID that will be my starting material.

Meanwhile, progress since my last post has been limited to finding a set of engine mounting plates that are in much better shape than the ones that came with this motorcycle. The next photograph shows how deeply pitted the rusted front plates are:

[Linked Image]

Compare the ones above with the condition of the "new" set I just obtained.

[Linked Image]
As can be seen, much of the black paint is still in place, especially on the right one, and where the paint is gone it has been replaced by surface rust without the deep pitting of the plates they will replace.

The current rear plates are even worse than the front ones, in that in addition to the deep pitting of the rust the the chrome plating added to them first would have to be removed before they could be sanded and painted. The next photograph shows one of the "new" rear plates propped into position above the peeling, rusted current one.

[Linked Image]
Again, much of the original black paint is still in place on both of the replacement rear plates.

Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 11/24/14 10:34 am

Have you considered sending your slides out for either Teflon or ceramic coating?

I just thought of that, but it's probably been done my more than a few folks already...

(Teflon skirts, ceramic tops)
[Linked Image]
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/24/14 11:19 pm

Originally Posted by GrandPaul
Have you considered sending your slides out for either Teflon or ceramic coating?
That's an interesting idea. Unfortunately, the bore is somewhat tapered as well as a bit oblong so even with a coating on a perfectly round slide to increase its diameter there would be an issue. Thanks for the suggestion, though.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 11/26/14 11:04 am

I would think that if a fellow was about to bore the carb for fitting a sleeve, he might first try to only bore it enough to clean it up, then coat the slide and see if he could get proper performance without going any further...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/26/14 4:10 pm

Originally Posted by GrandPaul
I would think that if a fellow was about to bore the carb for fitting a sleeve, he might first try to only bore it enough to clean it up, then coat the slide and see if he could get proper performance without going any further...
That's a very reasonable comment. I'm keeping my options open, but my present plan to install a brass sleeve would restore the body to its full strength. While I won't know for sure until I do the actual boring, the measurements I made make me think more than 0.010" will have to be removed from the bore to make it cylindrical.

Aside from the loss of strength, the 0.005" coating (i.e. 0.010" total increase in dia.) that would be required on the slide to give it the proper clearance makes me nervous for a few reasons. One is that is a thicker coating than seems to be typically applied for abrasion resistance. Another is the best properties seem to be with a form of PTFE that requires high baking temperature, which might cause warping of the slide. Another is that aimed-for carb/slide gap will be 0.004" so if a 0.005" flake came off the slide it could jam.

I like high tech solutions, but not when there are potential problematic issues to those solutions and I don't feel like being a guinea pig. In contrast, installing a metal sleeve will be more work but is a solution without worrisome issues. That's why I'm leaning toward the sleeve, although I haven't ruled anything out at this point.
Posted By: johnm

Re: 1957 BSA Spitfire Scrambler - 11/30/14 2:31 pm

I have never owned a BSA and had not noted this thread before.

However I have now read it and have to say it is just extraordinary!

The work, the research and the record keeping.

My congratulations !!

Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/03/14 2:49 pm

Thank you very much for your nice words.

Originally Posted by johnm
The work, the research and the record keeping.
My profession has required me to fabricate precision apparatus, conduct thorough research, and keep detailed notebooks. It's how I've worked for so many years that it's in my DNA, so Freud probably would say it was inevitable I would misuse this background when restoring a motorcycle.

I wrote earlier in this thread that whether or not any motorcycle deserves restoration at this level of detail is open to question. However, doing so imposes a certain discipline quite different than found in the "git 'er done" approach. Instead of the problem being, say, where to buy a replacement head for one with broken and missing fins, the problem to solve is how to repair those fins. Instead of the goal of each step being "good enough," the goal is "correct," irrespective of how much extra time is required.

No matter what, the choice of how one wants to proceed on a project like this is arbitrary. I arbitrarily set as my goal restoring this Spitfire to actual "museum quality" standards, not to something that typically is passed off as such. If nothing else this approach makes me think about solutions to problems that I otherwise would have quickly dismissed as impossible, so for me this Spitfire is a mental exercise as well as a physical restoration.
Posted By: Vetterdog

Re: 1957 BSA Spitfire Scrambler - 12/03/14 8:35 pm

I run into the problem of "it deserves/doesn't deserve to be restored" occasionally. I have a late 70s VW bus and I know lots of folks in the VW community who would let a late bus like mine rot into the ground because they only prize the earlier ones. It is really not a question of whether a machine "deserves" a restoration on any given level, since really these are just piles of neatly arranged metals, rubber etc., but a question of whether one can stop one's self from doing this work. I am currently finishing up a ten-year long A65 project, and am mentally preparing for the 74 Triumph that sits in my barn in various boxes and bins. Why? Because I can't NOT save these bikes. I'm sure you are the same way, and your skill set enables you to work on a highly inspired and inspirational level. Personally I am of the mind that I want to ride these bikes, and make them last. (The 3 britbikes I own would all have been scrapped if I hadn't grabbed them) I want to avoid roadside breakdowns, and hopefully be able to pass these on when my time comes. It would be wonderful if I had the knowledge, time, space and money to do complete museum restorations, but then the bike wouldn't be mine really; they'd lack the "custom" touches, the corners cut, the "make it work" ethos that defines who I am. Of course, I don't wish to detract from your masterful work, it is truly a joy to see, and thanks for being so diligent!
-Dave
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/06/14 6:16 am

Originally Posted by Vetterdog
Because I can't NOT save these bikes. I'm sure you are the same way,
Indeed I am the same way. In fact, that plus this Spitfire being serial #1, is what drives my approach to restoring this particular motorcycle since -- to me, at least -- "saving" it means restoring it to as close to factory-original as possible.
Originally Posted by Vetterdog
Personally I am of the mind that I want to ride these bikes, and make them last...I want to avoid roadside breakdowns,
The British expression "horses for courses" applies here. As opposed to my Spitfire, I restored/rebuilt my C15S to ride and be as reliable as possible because it lives in Ireland where I am only able to work on and use it for a week once/year. As a result I built it using a Mikuni carburetor, Chronometric speedometer (because I like it), and ET ignition (i.e. no battery) with Zener clipper diode array to keep from burning out bulbs. Until John O'Regan recently did a beautiful job of rebuilding it for me after 5000 miles of abuse it also had an aftermarket Al rear fender held together with pop rivets as a result of vibration taking its toll. However, the C15S does just what I want it to do in its "custom" form and I've never had any desire whatever to restore it to "museum quality." Different machines, different purposes, different approaches to their "restoration."
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 12/06/14 3:17 pm

Magnetoman, now that would be tough, having a bike across the big pond that you only get to use once a year. That said, a weeklong visit to Ireland once a year, knowing your bike is waiting there, would be a real treat. Is it on display somewhere? Stored/kept exercised by a friend when you aren't there?

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/07/14 7:17 am

Originally Posted by TR6Ray
Stored/kept exercised by a friend when you aren't there?
My C15S relaxes at a friend's house in Dublin 360 days/year, then is hauled to the other side of the country for ~500 miles on some of the finest motorcycling roads there are anywhere, in Counties Kerry and Cork. He's the one whose Bosch magneto I restored to use in two Cannonball runs thus far:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=446733#Post446733

I shipped the C15S to Ireland 12 years ago and keep a pretty extensive set of tools and spares with it to allow as much maintenance as is possible in hotel parking lots. However, although the bike is perfect for most roads, the friends I ride with are on 500s and 650s so there are times it has to pretend to be a 500. After ~5000 miles of thrashing it I left it in the very capable hands of John O'Regan in Cork to completely rebuild the engine (and cycle parts). There is only so much one can do in a parking lot, after all. Since then it has survived another ~1000 miles in the land beyond the Pale. I highly recommend John (and I don't make such recommendations lightly).

Not that you asked, but I geared the bike high, to give a calculated ~85 mph at redline, so as a result it cruises very smoothly at 45 mph (which is faster than most of the unpaved, single-track roads call for), and does 65 mph for extended periods without problem.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/13/14 6:44 pm

I returned from Tunisia a few days ago, and now I have a cold in addition to jet lag, so it will take a few more days before I'll be working with any tool much sharper than Photoshop. However, the brass tube for repairing the carburetor arrived while I was away so I now should have everything I need.

Using Photoshop to illustrate the problem by exaggerating it, the top image in the next illustration shows that the direction a carburetor flange is distorted when its mounting bolts are too tight against a soft phenolic spacer causes the side-to-side dimension of the bore to be pulled outwards, which in turn causes the fore-aft to be pulled inwards.

[Linked Image]

The result is that the bore distorts from being a cylinder into something oval-like when the flange is warped. Although this illustrates what happens, because the carburetor body isn't symmetric the actual cross-section will be more complex than a simple oval. Also, there will be different amounts of distortion at different heights within the bore. For example, the threaded portion at the top will remain nearly circular because it is relatively far away from the mounting flange (as well as reinforced by the cap). Still, although simplified, the top image in the above composite is a reasonable (exaggerated) representation of the distortion that has to be removed.

Since the slide remains cylindrical (at least in this simplified description), it should be clear from the top image in the composite that the slide will preferentially wear away the body of the carburetor in the fore-aft direction. Because of this wear, bending the mounting flange back to the proper flat shape as described in a previous post will still leave the bore oval-like in the fore-aft direction, with the worn-away portions indicated in red in the lower image in the composite. Again, though, the actual shape of the bore will be more complex than this. Also, even had there been no wear at all on the bore, bending the flange and then pulling it flat again would not return the bore to a perfect cylinder for the same reason bending a paperclip and then bending it back again only approximately restores its original shape.

With the above in mind I measured the carburetor with a Mitutoyo split anvil bore gage. I zeroed the gage at the bottom of the bore where, because of the tight fit of the jet block (which is now removed), the bore should have retained its original shape. After confirming this was the case by checking the zero both fore/aft and side/side, indeed the larger increase in bore everywhere along its length always was in the fore/aft direction. The position of maximum wear, 0.006", was just above the inlet track where the slide always is in contact with the body irrespective of how far open the throttle is. Here the amount of wear side/side was slightly smaller 0.005", also as would be expected from the above discussion. Overall, for the current shape of the bore imagine a pot belly stove squeezed to make it slightly oval in horizontal cross section.

I measured the original slide to see how much wear it had suffered. I used the top of the slide for these measurements since the metal is thick there. The fore/aft dimension had worn by fully 0.009" (i.e. 0.0045" worn from each face of the slide) with respect to the side/side dimension. However, the side/side dimension had almost no wear at all.

Luckily I have a NOS slide in the required 3-1/2 cutaway so now having determined what the wear pattern is, the task that remains is to sleeve the carburetor body. This will require fixturing the bore precisely parallel to the mill's spindle, centering it, and removing the necessary ~0.006" from the diameter to prepare the carburetor for a brass sleeve.

To be continued…
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/30/14 11:28 pm

Amal guru John Healy advises that 0.004" is the proper clearance for the slide so that's what it shall be. However, "clearance" is ambiguous by a factor of 2 (i.e. radial or diametrical), so to be clear on what he means by this it is ID(body) - OD(slide) = 0.004". However, other than confirming this important factoid I made very little progress on this restoration over the past two weeks. The only work I actually did was to machine a block to hold the carburetor body while I do the machining operations on it.

However, anyone following the Gold Star thread knows my excuse for this is I bought another Gold Star two weeks ago, and my spare time has been devoted to getting it fully operational. In current form it has a dummy dyno and no voltage regulator so one of the things I did was order the appropriate 6-PE Podtronics regulator from John's Coventry Spares. I have the necessary Chronometric speedometer and tachometer that I'll mount, but before the latter will work I'll have to machine the timing cover to take a tach drive (which I also have).

Other than those things the new-to-me Gold Star should be pretty much ready to go so it shouldn't be much longer before I'll be back to the Spitfire. Meanwhile, Happy New Year to everyone.

Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 12/31/14 10:22 am

Originally Posted by Magnetoman
However, "clearance" is ambiguous by a factor of 2 (i.e. radial or diametrical), so to be clear on what he means by this it is ID(body) - OD(slide) = 0.004".


Yes, just as with pistons and cylinder bores.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/11/15 2:56 am

A pretty 1957 Spitfire was just auctioned in Las Vegas.

https://www.mecum.com/lot-detail.cfm?lot_id=LV0115-200662

Someone asked me to check the numbers on it against the despatch record but they don't match, and details like the tank color, passenger grab rail, white piping on the seat, and carburetor drip tray stand out as incorrect. But, I was happy to see it sold for $16,000 because that means there's hope mine will be worth something someday. First, though, I have to finish the carburetor...
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/11/15 6:03 am

what's wrong with the drip tray most I have seen have them, including the brochures
paul
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/11/15 1:11 pm

Originally Posted by paul67
what's wrong with the drip tray most I have seen have them, including the brochures
I discuss the drip tray at several places in this thread, but you can see its absence at:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=497850#Post497850

Taking away a drip tray that shouldn't be there would be very easy, but I mentioned it because it's one of the discrepancies with the restoration that can be easily seen. What can't be seen is if it has the proper SCT2 gearbox, "big valve" head, or correct carburetor.

As for what can be seen or is known about this particular machine, recovering the seat and repainting the tank could be solved for ~$1000, but nothing legal/ethical can be done about numbers that don't match.

Maybe I should add that obviously it isn't that matching numbers make a bike run better. But, as has been discussed various times on BritBike Forum, they do add thousands of dollars to the "value" of a machine in the eyes of most buyers.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/11/15 1:39 pm

[Linked Image]
this add shows a drip tray fitted
Paul
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/11/15 1:56 pm

Originally Posted by paul67
this add shows a drip tray fitted
Indeed it does, but it's an ad for a later year, not the 1957 Spitfire.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 01/11/15 2:11 pm

I see a 57 add in the gold star buyer's companion that has one as well
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/11/15 2:55 pm

Originally Posted by paul67
I see a 57 add in the gold star buyer's companion that has one as well
That's certainly a source everyone needs to take very seriously...

Explained earlier in this thread are the reasons those magazine advertisements use a photo of a pre-production mock-up. See the post of August 15, 2013:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=501922#Post501922
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/29/15 4:07 pm

After interruptions due to travel, it's time to get back to the carburetor. The way I decided to approach this is to bore the carburetor by a sufficient amount to remove the distortion, install a brass sleeve with appropriate epoxy to restore the full strength, and bore the sleeve to give it the proper 0.004" clearance. But, all of that is easier said than done. As a reminder, two months ago (damn, how time flies…) I purchased a length of 1-3/8" OD, 1-1/8" ID brass tubing to use for this.

I first made a fixture to use the hole for the jet block to hold the carburetor in the mill's vise. Using this fixture I installed a sacrificial broken carburetor to test my plan. I couldn't assume the fixture holds the bore for the slide accurately parallel to the mill's spindle without confirming it. Since the bore is oval, tapered, and potbellied checking this isn't straightforward. If the bore were a perfect cylinder I would have used a dial test indicator, but here the best tool for the job is a coaxial indicator.

[Linked Image]

Using the coaxial indicator let me quickly determine the position of the "average center" of the not-quite-cylindrical bore at several heights. I assumed I would have to shim the holder to get the bore properly aligned but this turned out not to be necessary, at least with this sacrificial carburetor. I'll have to check this again once I start with the real one. After finding the center of the bore I locked the X and Y gibs and installed a boring head.

[Linked Image]

This machining operation requires a boring bar with a reach of at least 3" which increases the possibilities of both flexing and vibration. I first made a skim cut to make sure there were no issues and found vibration wasn't a problem but the finish left by the carbide boring bar is too rough so I'll switch to one with a HSS bit for the "real" carburetor.

[Linked Image]

My plan is to:
-- bore the carburetor to just above the air bleed holes, as shown in the next photograph,
-- measure the ID of the bored carburetor,
-- turn the OD of the brass to size,
-- install the brass sleeve with high strength epoxy,
-- bore the ID of the sleeve to give the correct 0.004" clearance for the slide,
-- open up the main air passage which at this point will be blocked by the sleeve,
-- drill the hole for the idle adjustment screw.

[Linked Image]

The above photograph is a view through the inlet after I had bored the sacrificial carburetor to just above the air holes. Since the slide only needs to reach the bottom of the inlet/outlet tract there is no point in making a sleeve that goes deeper than shown in this photograph.

Since the hole for the idle adjustment screw is at an acute angle, to get ready for drilling the hole in the brass sleeve after it is installed I made a bushing using one of the old adjustment screws I have in stock. The OD of this screw is very nearly 4.5 mm so, since I already had the collet holder installed in the lathe, the quickest way to do this was to drill a hole that diameter in an old "emergency" collet. As can be seen from the next composite, after installing the adjustment screw in the modified collet and removing the end I drilled a 1/8" dia. hole through it.

[Linked Image]

The drill bit tracked straight, emerging in the center of the head.

[Linked Image]

I made the hole 1/8" since that's the largest diameter that still left enough wall thickness in the modified adjustment screw for strength. After the sleeve is in place this bushing will guide a 1/8" drill bit to make a pilot hole without wandering despite the acute angle. I'll then remove the bushing and enlarge the hole slightly to the diameter used by Amal. Although 1/8" would work since the end of these adjustment screws is 0.116"-0.119" the holes in the half-dozen Monoblocs I measured vary from 0.129" (#30 drill) to 0.147" (#26) so I'll use a #28 (0.141").

-- to be continued --
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/01/15 1:16 pm

After tests with the sacrificial unit I installed the Spitfire carburetor in the fixture and centered and aligned it under the spindle in the same way as I had done for the sacrificial one. I also added a torque plate for no reason other than doing so seemed like a nice touch. The next photograph shows the Spitfire carburetor after boring, with the modified throttle screw/bushing and the brass sleeve whose OD I had turned to be slightly loose fit (i.e. ~0.001"-0.002" clearance).

[Linked Image]

I didn't make the sleeve a press fit because I wanted to leave a gap for the machineable epoxy. Even though the sleeve would be constrained from moving by the cap at the top and ridge at the bottom I wanted a physical bond between it and the body.

The epoxy I chose for this is Hardman 04002. The relevant specifications are a working time of 25 minutes so I didn't have to rush to get things into position or to wipe away excess epoxy that squeezed out, a service temperature up to 150 oC, and very good resistance to both gasoline and alcohol.

The manufacturer says the epoxy shows only 0.02% increase in weight after 8 days immersion in gasoline and 3.4% increase in 50% ethanol. Note that this epoxy isn't dissolved by gasoline or alcohol, only that it exhibits slight increase in weight after extended contact. Because of the slip-fit of the brass sleeve only a tiny amount of epoxy ever will be exposed to gasoline (diluted ~14:1 with air), and even then only when the engine is running. Making a linear extrapolation, 3.4% weight increase after 8 days immersed in 50% ethanol corresponds to only a ~0.3% increase in the thin exposed epoxy at the downstream outlet after running ~40,000 miles on E10 fuel. I count that as negligible.

Although the epoxy can be machined in less than a day, and is fully cured in seven, other obligations kept me away from it for more than two weeks. However, the first thing I did once I got back to it was to modify a boring bar intended for a lathe to reach the full depth. I then ground a HSS bit with a slightly rounded point and honed the cutting surface to give the smoothest possible finish on the brass.

Throughout all of this the carburetor had remained locked in the vise (and the DRO left 'on' so I could accurately reposition the table after I moved it to make measurements) so I first faced the top to match the height of the carburetor as shown in the next photograph.

[Linked Image]

Next I measured the OD of the slide I will use. The top of any slide is the most important part since its thickness means that although it could be worn it wouldn't be subject to distortion like the thin skirt could. Anyway, the slide is very nearly round, varying by only 0.0005" in either direction from an average of 1.309". This means I need to make the bore 1.313" (i.e. 1-5/16") to give the recommended 0.004" clearance (actually from 0.0035" to 0.0045" if I hit the target diameter perfectly).

Although the boring head I used has markings every 0.0001" in diameter, moving the bar outward by that amount doesn't necessarily mean it will cut that from the diameter, so I can't "sneak up" on the final diameter by taking tiny cuts. If the attempted cut is too light it's quite possible for the bit to slide over the surface without removing any metal at all. If the attempted cut is too heavy the relative lack of substance to the carburetor easily could result in vibration and distortion. If I were to restore carburetors frequently, which I don't plan to, I would make a fixture to support the carburetor more rigidly in the mill. Anyway, these factors, plus springiness of the boring bar and of the brass, made the process of producing the bore to a precise dimension a fairly time consuming one of cut, move the table to gain access to the bore for measurement, reposition back under the boring head (using the DRO's resolution of 0.0002"), adjust the boring head to a new diameter, make the next cut, [repeat].

By making a cut, accurately measuring the resulting diameter, adjusting the boring head by a known amount, and then going through another cycle of cut and measurement I knew by how much I had to compensate for springiness. Based on such measurements I decided to make my final cut when there was somewhere around 0.010" remaining to be removed from the diameter. When I got to the point where the bore was 0.0073" under my goal my final cut should have left it precisely 0.0040" larger in diameter than the slide. As the next photograph shows, I came within 0.0002" of hitting this.

[Linked Image]

For the above measurement I zeroed the split-anvil gage at the diameter of the slide (and with the small needle on '3') so the position of the large needle counterclockwise from '0' shows the amount by which the ID of the bore is larger than the OD of the slide, i.e. just at 0.0042". Actually, I'm pretty sure I could have hit precisely 0.0040" had I spent another half-hour prior to making the final cut. However, since 0.004" is a somewhat arbitrary number anyway (for all anyone knows, even if there were such a thing as an "ideal" clearance it might be, say, 0.0043"), and the slide is out of round by +/-0.0005" anyway, so there was no point spending the extra time to precisely hit an arbitrary number to the nearest ten-thousandth. Before removing the carburetor from the vise I used an end mill to open up the notch for the cap.

The way I did this machining should have resulted in the brass sleeve being concentric with the hole I had previously bored in the body to within 0.0002", which in turn is as close as I could make it concentric with the original bore. Although there is no way for me to check, I estimate errors in alignments and tilts of the brass ID with respect to how the carburetor left the factory are no more than ~0.002", which is negligible.

I'm still not done, but the most time-consuming aspect of this is over (I hope), and the carburetor now fits the slide like a bespoke Savile Row suit. I still have to bore out the inlet and outlet and drill the hole for the idle adjustment screw, then reassemble it and move on to the next task in restoring the Spitfire.

-- to be continued --
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/06/15 2:43 pm

Nearing the end, the almost-final steps are to bore the portions of the brass sleeve that are currently blocking the inlet and outlet, which requires accurately locating the centers of each. A brave person might try to fixture the axes of the carburetor perfectly horizontal and vertical and then run the boring bar straight through to cut both openings on a single pass. However, the slightest error in fixturing makes that foolish to even contemplate. Instead, I separately bored each hole.

A mill doesn't have to be level in order to function correctly but if it is it speeds things up for a job like this. I turned a scrap piece of 1.5" Al bar down to 1.3" to slip inside the bore and, as the next photograph shows, used it along with the vise and my jet block fixture to clamp the carburetor in the correct horizontal orientation in order to remove the brass from the outlet side of the air tract.

[Linked Image]

The machinist's level sitting on the mounting flange has a sensitivity of 0.001"/10" making it quick and easy to align the flange along X and Y to greater accuracy than needed for the next milling operation. Note that the bottom of the bore is held in "dynamic tension" between the jack on the bottom of the carburetor and the clamp on the top of the Al bar so there is no force acting to distort any part of the body. Also, I sneaked up on the final clamping pressures by successively increasing the tension on the vise, jack, and toe clamp, all the while keeping the bubble centered in the level. I used only a fairly small clamping force between the jack and toe clamp since the main purpose was to ensure the carburetor remained level when subjected to the downward force of the end mill. In principle, the jack alone would have been sufficient for this, but clamping also helps eliminate vibration.

As I had done for the main bore I used a coaxial indicator to align the center of the outlet directly under the spindle. The outlet bore turned out to be so accurately round that I was able to align it well enough that I couldn't see the needle of the indicator waver at all, so it was better than ~0.0002" I then used a 3/4" end mill to open a hole in the brass into which the boring bar would fit. I used an end mill rather than a drill bit for this to eliminate the possibility of the cutting tool grabbing the soft brass of the relatively thin sleeve.

Next I installed the same boring/facing head I had used previously. When the adjustment ring used to make incremental advances of the tool bit for boring is held while the head is rotating it advances the bit by 0.005"/revolution for facing operations. This let me quickly open up the hole ~0.01" at a time until visually there were only a few thousandths remaining to be removed, at which point I switched to advancing only ~0.001 at a time. After I finished boring the outlet I flipped the carburetor by 180-degrees and did the inlet the same way.

The last bit of machining should have been simply to drill the hole for the idle adjustment screw. Unfortunately, this is one of those times where what I assumed would be trivial was more work than expected. It turned out there was enough distance between the end of the bushing I described two posts previously and the edge of the brass sleeve that the 1/8" drill bit deflected. Since a drill bit is designed to cut with its tip, not its sides, this left the hole in the brass too far offset for the idle adjustment screw to pass through, turning what should have been a trivial task into more of an ordeal than I had imagined. Sigh…

The small amount of metal that needed to be removed was too deep inside the carburetor for a Dremel stone or carbide burr to reach it from up through the hole for the idle screw, and the diameter of the Dremel motor was too large to fit inside the ~1.3" ID of the brass sleeve from the top. So I made an extension for a 9/64" (0.141") miniature end mill using a piece of 1/2"-dia. Al rod from the scrap bin. Steel would have been more rigid but that wouldn't be an issue given the small amount of brass than needed to be removed. Since the Al rod was the perfect diameter to reach the necessary depth at the required grazing angle and with sufficient rigidity I used it to make a holder for the end mill as shown in the next photograph.

[Linked Image]

Alignment for this operation is important but not extraordinarily critical so I used a precision square to align the outside of the casting for the idle screw vertical in the vise. As can be seen from the first photograph in the previous post the carburetor is tilted by ~10-deg. when the hole for the idle screw is vertical. It was then easy enough to position the end mill by eye by looking through the inlet, after which it only took a few seconds to deal with the excess brass. With the machining finished, the next photograph shows the completed carburetor.

[Linked Image]

Grateful that the Spitfire only has one carburetor to deal with, all that remains to do now is to clean, reassemble, and put it on the shelf to await installation once I rebuild the engine.

A few final notes: Although I have plenty of spare Monoblocs, only this one has the correct 376/89 markings for a 1957 Spitfire. Consequently, I inched forward cautiously every step of the way. However, now that I've established a procedure that I know works (and have made the necessary fixtures, jigs, etc.), if I were to restore a second one at this point I'm pretty sure I could do it in a couple of hours while still proceeding with ample caution.

Although I can't be the first person to have done this, I can't remember having seen a description of a carburetor restored this way before. While the "commercial" way of boring the carburetor body and sleeving the slide certainly would have been faster, the advantage of my approach is that the carburetor is now back to its original specification, and retaining its full strength, so standard slides with different cutaways could be substituted without problem if necessary for tuning with the ever-changing modern fuels. This is not possible with a sleeved slide. Also, while it's unlikely enough miles would be put on any such rebuilt carburetor to wear out the brass sleeve, if that ever happened a new one could be installed in the same way as the first one and the carburetor again would be as-new. With a sleeved slide the body would have to be bored out even more, weakening it further, and an even larger diameter sleeve installed on the slide.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/09/15 1:02 pm

Originally Posted by gREgg-K
Excellent work as usual, MM! There is a significant advantage to the way you did it, too.

When boring the sleeve the way you did, you avoided having an interrupted cut as the cutting tool passed by the venturi ... which is a problem with the more common 'sleeved slide' technique.

.. Gregg
I took the liberty of copying Gregg's post from a different thread. First, thanks for the nice comment. I know that Gregg also enjoys machining so he caught this point.

I added a lot of frequent flyer miles to my accounts since I realized in November that the wear + distortion was too much to deal with in any other way than sleeving, so I had a lot of time at altitude to think about how to proceed.

As just one example, I could have skimmed only just enough from the carburetor body to eliminate the distortion (say, 0.010"), installed the brass (or stainless, or bronze, or...) in the same way I did in this thread, and then machined the bore to size. However, that would have left a very thin tube of brass and my concern was it could rip in subsequent operations to open up the venturi. Instead, I could have left the sleeve at full thickness so ripping/tearing wouldn't be a concern, machined the venturi first, and then machined the main bore. But that would have required an interrupted cut and possible rough/wavy surface as mentioned by Gregg.

As I wrote earlier, having never seen a description of sleeving a carburetor this way I was on my own in determining how to proceed, with the consequence of an incorrect decision pretty severe since it had taken years to find this carburetor, and a saved search on eBay has not turned up another since then. Because of this I spent a lot of extra hours restoring this carburetor that wouldn't be required if I ever have to do a second one. But, it still would be faster to bore the body and sleeve the slide as commercial operations do it so I don't expect them ever to do it "my" way despite the clear advantages.

Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 02/09/15 5:25 pm

I can only imagine the anxiousness of certain anti-rivet-counters who might "force" themselves to read some of these posts!

Threads like this enforce my undying joy at having chosen classic bikes as my hobby...

(it really is as fun to work on them, as it is to ride them)
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/10/15 1:12 pm

Originally Posted by GrandPaul
I can only imagine the anxiousness of certain anti-rivet-counters who might "force" themselves to read some of these posts!
They can't say they weren't warned. I wrote in the first paragraph of the first post of this thread that I was going to use "an approach to restoring a motorcycle that not everyone will want to copy."
Originally Posted by GrandPaul
Threads like this enforce my undying joy at having chosen classic bikes as my hobby...
(it really is as fun to work on them, as it is to ride them)
I appreciate your appreciation.

The company Luminosity advertises that playing their games can increase memory and problem solving skills. Their claim is at the end of spending time playing their games your brain will be better for it (or, at least, you can play the specific games they're marketing better than before). If this is the case, actually solving real, not made up, problems like how to sleeve a carburetor should makes my brain better for it and at the end result in me having another working motorcycle. Sign up for BritBikinosity today: Improve your brain and get a motorcycle.
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 02/10/15 4:43 pm

Originally Posted by GrandPaul
I can only imagine the anxiousness of certain anti-rivet-counters who might "force" themselves to read some of these posts


Bit hard GP, I am far from being a rivet counter, and personally if it meant me sending an original carb away to be referbished or buy a replacement, I would simply buy a replacement. However I can't help but admire the detail and skilled work put in on this motorcycle and is the true definition of restoration.

I look forward to seeing the finished article.


Posted By: Alex

Re: 1957 BSA Spitfire Scrambler - 02/10/15 5:19 pm

This is good stuff, MM. I actually have an 89 amal that was sleeved in this way. It was either done very crudely or suffered much abuse after the job (the rest of the bike certainly did). It does look like it was run in this way for some time.
Posted By: zoe

Re: 1957 BSA Spitfire Scrambler - 02/12/15 11:38 am

I appreciate the reference to Luminosity. When I'm in the middle of figuring out some problem with my bike (not nearly as complex as what MM does) I feel it is helping to preserve what brain power I have remaining; at least that's my excuse to my wife as to why I always must have a bike project and another bike project.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/21/15 10:38 pm

I finally finished a small job I started only 20 years ago. The tension on the steering bearings is set using the "steering stem adjusting sleeve" shown at the right of the next photograph.

[Linked Image]

BSA gave us a rather crude way of turning this sleeve in the form of six 1/8" slots at the top. The owner could use a flat piece of metal slightly thinner than 1/8" to turn the sleeve, but I suspect typically uses a screwdriver and hammer. Of course, beyond making fine adjustment problematic, this distorts the threads at the top making it difficult to put the cap on the sleeve after all the hammering is done.

When I first loosely assembled the Spitfire's forks many years ago I designed a sprag socket to do the job properly, started to make it, and then let it sit unfinished because I no longer had easy access to the sleeve to check for fit. However, a few months ago I acquired a horde of parts for BSA singles, included in which were a few of the sleeves. So today I installed the rotary table on the mill and finished the socket. The socket is on the left of the above photograph with the "fingers" that fit into the slot painted black to make them stand out better. The next photograph shows how the socket fits on the sleeve.

[Linked Image]

I'm now ready to deal with the forks without a hammer when that time comes.

In case anyone is interested in details, I started with a 1" impact socket, did most of the metal removal using a 1/4" end mill, but then used a 1/8" end mill to give the 6 "fingers" a somewhat more rectangular profile.
Posted By: paul67

Re: 1957 BSA Spitfire Scrambler - 02/22/15 4:21 am

And paten and make your socket so those of us with out a milling machine can buy them
Paul
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/23/15 11:21 am

Originally Posted by paul67
And paten and make your socket so those of us with out a milling machine can buy them
Another very useful tool BSA should have made is for the engine sprocket:

[Linked Image]

and yet another is for the gearbox sprocket:

[Linked Image]

Given the number of specialty tools BSA did make the fact they didn't supply these two seems to be a significant oversight on their part.
Posted By: BritTwit

Re: 1957 BSA Spitfire Scrambler - 02/23/15 7:52 pm

I think I saw one of these at Harbor Freight. $4.99 and a life time warranty.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/24/15 12:42 pm

Originally Posted by BritTwit
I think I saw one of these at Harbor Freight. $4.99 and a life time warranty.
You must not have received their latest catalog yet. With the 20% discount coupon the full set of all BSA specialty tools is $6.99. And don't forget the free flashlight.
Posted By: L.A.kevin

Re: 1957 BSA Spitfire Scrambler - 02/24/15 4:35 pm

Originally Posted by Magnetoman
Originally Posted by BritTwit
I think I saw one of these at Harbor Freight. $4.99 and a life time warranty.
You must not have received their latest catalog yet. With the 20% discount coupon the full set of all BSA specialty tools is $6.99. And don't forget the free flashlight.


Here's a handy sale paper (really, read it, you'll chuckle)
http://www.flutterby.com/images/2012/10/01/hf_tool_sale.pdf
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/27/15 4:06 pm

Originally Posted by L.A.kevin
Here's a handy sale paper ...
I highly recommend the hydraulic nail unbender. It's perfect for straightening spokes.
Posted By: alibaba

Re: 1957 BSA Spitfire Scrambler - 03/02/15 7:24 pm

Please correct me if I am wrong - maybe I misread but I think you stated that the crate you purchased contained an A65 frame and a engine that at the time appeared to be an A10 and that the frame was correct for that engine. However, the A65 frame was not produced until much later with the advent of the unit construction A65 'egg' engine. Have I misunderstood something here?
Posted By: Les P

Re: 1957 BSA Spitfire Scrambler - 03/02/15 7:36 pm

I read it as the A65 frame was a spare and part of the deal along side the the original engine and its own compromised frame.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/02/15 10:54 pm

Originally Posted by Les P
I read it as the A65 frame was a spare and part of the deal...
Exactly. I got it in the early 1990s, and A65s had been around for 30 years by then, so no time warp was required for there to have been an A10 and an A65 frame in the same crate as an A10 engine.

Thanks for your nice comment about this thread.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 03/08/15 12:37 am

This post has nothing to do with the Spitfire but it seems worthwhile to post here anyway in light of the recent Monobloc refurbishing.

The BB Gold Star I got a few months ago came with a Concentric whose slide would stick in the fully open position (luckily, discovered in my garage when it wasn't running). When I took it off I found the flange had been ground flat, as shown in the next photograph, no doubt to "fix" bent mounting ears.

[Linked Image]

Unfortunately, this "fix" eliminated the possibility of bending them back like I did with the Spitfire's Monobloc which would have removed much of the distortion that was causing the slide to bind. However, rather than toss it out I decided to see if I could make the carburetor functional again despite this. I installed a pipe expander to try to remove some of the distortion but after a week there was essentially no difference.

[Linked Image]

So, I machined a jig from a bar of Al to accurately and firmly hold the carburetor and then centered the distorted body in my lathe as best as possible under the circumstances.

[Linked Image]
The distortion was such that it was very difficult to even begin to insert the slide from the top so I sneaked up on the cut by removing ~0.001" from the high spots on each side of the upper ~1/8" of the body, tested to see if the slide would fit, removed a little more, found it would fit, and extended the cut to ~1/4". By proceeding slowly this way I found I only had to advance the boring bar by 0.002" from when it first touched in order to allow the slide to move freely, and only to a depth of ~1" below the top. At that point the slide traveled freely the whole length.

If you look closely at around the 5:00 position in the bore you will see an irregular patch, which is where the high spot was removed. There also was some material removed near the 11:00 position. Basically, 0.002" was removed from each high spot.

Since the boring bar only entered ~1" the amount of slop with the throttle almost closed (where the slop matters most, because it is there where it disrupts the idle) is the same as when I started since I didn't have to bore to that depth.

While I had it apart I made sure the pilot jet was open and I measured the needle jet. The .106 needle jet was quite worn at nearly a .107 (it was 0.1069"). Anyway, although this Concentric is worn it is functional again. However, I will be putting a Monobloc on the Gold Star instead, but have a few more changes and tweaks to make to the bike before making the swap.

Back to the Spitfire restoration…
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 04/26/15 9:27 pm

(I'll be posting this same question on the Gold Star forum)

In a post on 23 August 2013 I discussed the evidence for this Spitfire's tank being silver:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=503093#Post503093

However, what shade of silver? We know that BSA didn't apply the same level of quality control to batches of paint as they did when they made their... well, their, um... oh, never mind. Anyway, luckily this means I don't have to hit some specific shade to the nearest 0.001 on the CIE chromaticity diagram. However, I do want a shade within the range of ones that would have come out of the factory. So, I would greatly appreciate it if someone could point me to discussions of the shades of silver appropriate for a BSA Gold Star. In the end I need to know the color in the form of a paint used on a modern car, e.g. "2015 Volkwagen Cool Silver."

Also, there's a red pinstripe that separates the silver from the chrome. What shade is the red, and how wide is the pinstripe?

Thanks very much in advance for any and all help with this.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 04/27/15 5:45 pm

Only ref I can find is VW beetle silver. The red may be Post Office Red which is a British Std colour.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 04/27/15 7:03 pm

Originally Posted by kommando
Only ref I can find is VW beetle silver.
I just checked but, unfortunately, starting in 1957 VW had dozens of silvers -- strato, polar, aero, diamond, ... -- although for three years one of their silvers was "silver." Further, the manufacturer's code for, say, polar silver was L324 in 1957, but LA7V in 1984, L37M in 1987,..
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 04/28/15 7:24 am

I have a vision of the German engineers walking the car park looking for a suitable Silver and finding a row of Gold Stars, on finding they vary in shade they get a paint code for each one and use them over the years.

Best source in UK for BSA paint matches is

Polly Palmer
Address:
Cwmsannan House
Llanfywydd
Carmarthen
Postcode: SA32 7TQ
Country: UK
Telephone: 01558 668579 / 07702 726230
Fax: 01558 668579
E-mail: [email protected]

and read http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=340652
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 04/28/15 3:34 pm

Originally Posted by kommando
Best source in UK for BSA paint matches is…
…and read http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=340652
Thanks very much for this information. I used the 'search' function before posting my question but it hadn't turned up Swan's posts. On the Gold Star thread MrBSA posted details of appropriate paints for the tank and pinstripe. Also, I sent an email to Polly Palmer a little while ago and will report back what he tells me. So, thanks to all the help, I'm zeroing in on what will be the best match.

Originally Posted by kommando
I have a vision of the German engineers walking the car park looking for a suitable Silver and finding a row of Gold Stars, on finding they vary in shade they get a paint code for each one and use them over the years.
VW using Gold Star tanks to determine the color of silver for their cars, which now is used to determine the color of Gold Star tanks, reminds me of a story. Whether or not it actually is true, a story that deserves to be is that for some time the guy in charge of Big Ben set it according to the chime that used to play on the hour on the BBC. However, the guy in charge of the clock at BBC set it according to Big Ben. Because of the intrinsic error of such unintentional feedback both clocks finally drifted enough that someone noticed there was a problem.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 04/29/15 7:01 am

No mention of the Big Ben issue on Wiki, it does mention other problems but wiki is not 100% accurate.

http://en.wikipedia.org/wiki/Big_Ben


I no longer use the forum search, instead I use google and put the subject of the thread and britbike.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 04/29/15 1:58 pm

Originally Posted by kommando
No mention of the Big Ben issue on Wiki, it does mention other problems but wiki is not 100% accurate.
Like I said, even if that story isn't true, it should be because it is a great illustration of the effect of that type of unintended feedback.

Not that it means anything about the possible accuracy, I'm pretty sure I heard it on the BBC itself some 20-30 years ago. The version of the BBC you get in the UK is different than the one they send out to the rest of the world to indoctrinate us. At that time the world news on the hour started with a countdown of beeps, with the last one at the precise hour being longer. Hence, the story of feedback between BBC and Big Ben is completely plausible, whether or not it is actually true.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/01/15 12:58 pm

Originally Posted by kommando
Best source in UK for BSA paint matches is

Polly Palmer
Address:
Cwmsannan House
Llanfywydd
Carmarthen
Postcode: SA32 7TQ
Country: UK
Telephone: 01558 668579 / 07702 726230
Fax: 01558 668579
E-mail: [email protected]
First, two corrections to the above information. My emails bounced back with an error message implying there was a problem with the server at the other end, but it turns out the address above is missing a crucial '.' It should be britie.motorcycles.

The second correction is they don't accept faxes anymore. When using an overseas fax number for the first time I always try during daylight hours their time so I don't wake anyone up if there is a problem with the number. In this case Polly himself answered, and was very cheerful and happy to help.

He told me is he recommends 'Rolls Royce Silver', which he said is a glossy paint but not a metallic (however, after I hung up and checked on Rolls Royce colors I found three silvers: 'silver chalice', 'silver mink', and 'silver sand'). Also, he recommends 'British Post Office Red' for the 3/16" stripe.

When I questioned him about how he arrived at these recommendations he said something like "I held cards up against the tank and they seemed to match pretty good." Hmm, that's what I was afraid of. Even after sorting out the chalice/mink/sand issue, "pretty good" isn't what I'm aiming for. So, more research is needed.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/24/15 3:35 pm

This Spitfire restoration has been effectively on hold for a while to allow me to get a few other bikes fully roadworthy. Despite that I spent a little time today testing aluminum cleaners to be sure I have something appropriate on hand when I'm ready to finish the Spitfire's gearbox.

A few weeks ago I bought the only two brands of wheel cleaner stocked by a local auto parts store:

Meguires Hot Rims Aluminum Wheel Cleaner
Mothers Polish Aluminum Wheel Cleaner

I did two tests of these today, one on a piece of scrap aluminum stock (probably 6061 but I'm not sure) and another on a B31/B33/GS timing cover. I first cleaned the pieces with acetone to remove all grease, then masked strips on them and applied the cleaners in succession following their directions. The Mothers made a barely perceptible difference on both pieces, but I could see no effect whatever of the Meguires. I didn't bother photographing the results because the effect is so small that I doubt if it would show up.

I have Scotchbrite, buffing wheels, rouge, soda blaster, etc., so mechanical polishing isn't the issue. I want an aggressive cleaner that will slightly attack the half-century of dull grey aluminum oxide without etching more than a few microns from the sand-cast texture. The directions on one of the containers talks about waiting for the "foaming action" to cease, which made me think it would have a slight amount of a weak acid or base in it, but the only foaming exhibited was that of soap bubbles that formed as a result of the spray.

Clearly I'll have to research this further to find a commercial product formulated for dirtier wheels than the above two are meant to deal with.
Posted By: RGSDave

Re: 1957 BSA Spitfire Scrambler - 05/24/15 10:27 pm

The best results that I have found for cleaning aluminum cases is PB Blaster and a grey Scotchbrite. It is very labor intensive and if you have arthritic knuckles like myself, it can be very difficult. The initial results will be a brighter finish than you probably desire, but will tarnish off in time.

[Linked Image]

There is also a wheel cleaner that I use from time-to-time that is sold by Keystone Automotive, purple in color, and smokes when you put it on aluminum - it is very caustic.

Dave
Posted By: robcurrie

Re: 1957 BSA Spitfire Scrambler - 05/24/15 10:28 pm

Most aluminium wheels are powder coated or painted.
Rob C
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 05/25/15 4:20 am

The milder alloy cleaners (also referred to as brighteners) normally have Phosphoric acid in them, the more aggressive ones have Hydrofluoric acid which is nasty stuff.

http://www.omegachemical.com/safety/bright_burns.htm
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 05/25/15 8:59 am

Try some oven cleaner. I can't remember the name of one I used to use that worked quite well on old cases. It does dull them, but THEN you use the Mother's to brighten back up to original brightness.
Posted By: Zombie

Re: 1957 BSA Spitfire Scrambler - 05/25/15 9:15 am

Originally Posted by kommando
The milder alloy cleaners (also referred to as brighteners) normally have Phosphoric acid in them, the more aggressive ones have Hydrofluoric acid which is nasty stuff.

http://www.omegachemical.com/safety/bright_burns.htm



I had to correct this.
HydroFLouric acid is deadly to humans... http://en.wikipedia.org/wiki/Hydrofluoric_acid Aqueous hydrofluoric acid is a contact-poison with the potential for deep, initially painless burns and ensuing tissue death. By interfering with body calcium metabolism, the concentrated acid may also cause systemic toxicity and eventual cardiac arrest and fatality, after contact with as little as 160 cm2 (25 square inches) of skin.

HydroCHoric acid is what you mean... http://en.wikipedia.org/wiki/Hydrochloric_acid Hydrochloric acid has been used for dissolving calcium carbonate, i.e. such things as de-scaling kettles and for cleaning mortar off brickwork, but it is a hazardous liquid which must be used with care. When used on brickwork the reaction with the mortar only continues until the acid has all been converted, producing calcium chloride, carbon dioxide, and water:

Hydrochloric acid IS commonly used to clean aluminium, and it's sold in hardware stores as either brick wash, masonry wash or swimming pool PH stabilizer.

Two letters in one word make a HUGE difference.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 05/25/15 9:53 am

I do mean Hydrofluoric and it is in alloy brighteners hence the link to a site on Bright burns which tells you about Hydrofluoric acid. And it is nasty and I would not use it but it is used.
Posted By: Zombie

Re: 1957 BSA Spitfire Scrambler - 05/25/15 10:15 am

LOL Is really inappropriate here but I had to laugh...

Quote from your link...
Almost all Aluminum Brighteners contain a percentage of Hydrofluoric Acid. (CAS 7664-39-3). This acid is ranked among the compounds most hazardous to human health. The danger of an Aluminum Brightener burn is that it can rapidly penetrate the layers of skin, making flushing with water alone ineffective.

It's like using uranium to solve a mouse problem. I thought the use of Hydroflouric acid was banned YEARS ago.

I stand corrected sir.

Anyone that reads these couple of posts, PLEASE stay away from that stuff. There are lots of articles on people that have died using it.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/25/15 2:37 pm

Originally Posted by RGSDave
PB Blaster and a grey Scotchbrite. It is very labor intensive ...
Labor is what I'm trying to avoid as much as possible. Better living (and cleaning) through chemistry.
Originally Posted by kommando
(also referred to as brighteners) normally have Phosphoric acid in them, the more aggressive ones have Hydrofluoric acid which is nasty stuff.
Originally Posted by Zombie
Anyone that reads these couple of posts, PLEASE stay away from that stuff. There are lots of articles on people that have died using it.
Not having researched it I didn't know there was such a product as "aluminum brightener." I don't have a bottle of one of the commercial products to refer to but I'm sure the directions instruct the user to wear gloves and goggles. I would advise anyone to read and follow instructions for all chemical products. Of course, entirely avoiding the use of any problematic chemical (e.g. brake fluid or brake cleaner) may be an option for some, but using the products -- following directions -- is my preferred path. As for HF, I've had bottles of concentrated HF around for over 40 years and always have treated it with great respect whenever using it because of its hazards in concentrated form.

Learning from these posts that something called "aluminum brightener" exists and has HF as one of its constituents reminded me of something from my earlier days. I actually have a U.S. patent (along with two colleagues) for a chemical etch for thin films of the metal niobium. Along with nitric and sulfuric acids, a critical ingredient of our etch is HF which has to be present in a fairly narrow concentration range. Too much HF and it etches way too fast; too little and it takes forever. The function of the HF is to remove the oxide from the niobium allowing the other acids to then do their work on the metal itself. When a piece of Nb is placed in the etch nothing seems to happen for a moment, after which the metal starts etching. That initial "pause" is it time it takes for the HF to remove the protective oxide film. Removing the oxide also is why HF is in "aluminum brightener."

Anyway, thanks guys for bringing the existence of "aluminum brightener" to my attention. Such a chemical is just what I was hoping for. After finding where to buy it I'll try it out on test pieces following instructions and at full recommended strength (plus several dilutions if full strength seems like more chemical h.p. than needed) to make sure it leaves the Al brighter, but not unnaturally so. I'll report back with my findings in due time.
Posted By: Zombie

Re: 1957 BSA Spitfire Scrambler - 05/25/15 7:20 pm

I was looking around for some of the product, and I found that AlumiBrite, http://www.enviromfg.com/pdf/Alumi-Brite%20Literature%20WSO.pdf
is boasting the fact that they do NOT use hydrofluoric acid. There are still several brands that do use hydroflouric acid still available.

I'm happy to hear that you have a working knowledge of chemistry, and recognize the hazards. I have the typical "guy" habit of glancing at the directions, and jumping in the deep end. Hazard warnings are made for fellas like myself. To bad I don't read them...
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 05/26/15 3:20 am

The Brighteners work by removing the Aluminium Oxide layer and revealing the original fresh as cast aluminium alloy. With phosphoric acid this needs good timing as after the oxide has gone it then takes a look at the alloy and starts to convert it to aluminium phosphate which is a dark grey and more unsightly than the oxide. The reaction speed is slow so its easy to find the sweet spot but do check every 15 mins or so. When used on steel phosphoric acid first removes all the iron oxide and then creates a surface layer of iron phosphate, as its density is close to steel it acts as an anti corrosion layer. Not sure what the Hydrofluoric acid does after its eaten the aluminium oxide.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/26/15 6:36 pm

Originally Posted by Zombie
I found that AlumiBrite ... is boasting the fact that they do NOT use hydrofluoric acid.
Originally Posted by kommando
With phosphoric acid this needs good timing as after the oxide has gone it then takes a look at the alloy and starts to convert it to aluminium phosphate which is a dark grey and more unsightly than the oxide.
Last year I asked my wife to pick up some TSP (trisodium phosphate) to use on oil stains on the garage floor of the house we were moving out of. Instead, she bought a better-for-the-environment "TSP Substitute". Hey, I'm much more of an environmentalist than the average guy (save your comments about the hypocrisy of me claiming this while riding oil-spewing bikes), but the bogus-TSP was worthless. There certainly are excellent reasons to avoid using tricholoethylene, asbestos, Freon, etc. but that doesn't mean substitutes for them are as good as the originals in all applications. I'll take my aluminum brightener with HF, thank you very much.

Unfortunately, this stuff isn't easy to find. Over the past few days I stopped at four auto parts stores, an automotive paint wholesaler, and a car wash wholesaler. The latter actually has the stuff, but only in 55-gallon drums. However, not having a large truck to brighten, or a car trunk big enough to fit the drum even if I did, I decided to pass on it and continue looking. After cross-checking brands with MSDS sheets to eliminate environmentally-friendly, bio-degradable imposters, I found the good stuff on Amazon for about $50/gallon including delivery.

Studying a few MSDSs to figure out the composition, my best estimate is these brighteners consist of ~10% (20% max.) HF, 3x that in ammonium fluoride as a buffer, and a few percent 2-butoxethanol as a surfactant (to reduce the surface tension and allow it to wet the surface better). Hmm, that sounds familiar. Checking the composition of the "buffered oxide etch" used to remove the oxide from silicon wafers, it's essentially the same, although without the surfactant that would be an unwanted contaminant. The etching rate of ~2 nm/sec. for the oxide is just right for our uses, and the CRC handbook lists the solubility of pure Al in HF as very low so it shouldn't attack the Al once it's finished with the oxide. However, castings are alloys so it would be nice to confirm compatibility with HF before spending the $50. Luckily, since I have a C11 engine in my office (doesn't everyone?), I did a quick test using its timing cover and got excellent results. The only qualification is that the part has to be clean for the HF to do its work.

Depending on shipping costs, buying the constituents and mixing my own likely would be cheaper than $50/gallon, but more of a hassle, so I'll have to decide whether to do that.
Originally Posted by Zombie
I have the typical "guy" habit of glancing at the directions, and jumping in the deep end.
I sat through enough safety training lectures over the years that no doubt I'm more aware of the consequences than most. Plus, many years of being responsible for young people working around chemicals, x-ray equipment, etc., where how I behave myself directly influences how they behave, has had an effect as well. Through at least their 20s most people think they are immortal so even where I know from experience I could safely take shortcuts it would be irresponsible to do so when those others are around. Assembling a kid's bicycle without reading the directions is one thing, but jumping in and working blind, so to speak, with corrosive/toxic substances is quite another.
Posted By: johnm

Re: 1957 BSA Spitfire Scrambler - 05/27/15 1:27 am

Originally Posted by Zombie
I was looking around for some of the product, and I found that AlumiBrite, http://www.enviromfg.com/pdf/Alumi-Brite%20Literature%20WSO.pdf
is boasting the fact that they do NOT use hydrofluoric acid. There are still several brands that do use hydroflouric acid still available.

I'm happy to hear that you have a working knowledge of chemistry, and recognize the hazards. I have the typical "guy" habit of glancing at the directions, and jumping in the deep end. Hazard warnings are made for fellas like myself. To bad I don't read them...


Yes MM has probably got a reasonable working knowledge of chemistry. :-) He was outed on another thread so you can make a call on the quality of his engineering (and advice) from this !

http://www.optics.arizona.edu/research/faculty/profile/charles-m-falco
Posted By: Zombie

Re: 1957 BSA Spitfire Scrambler - 05/27/15 3:38 am

Originally Posted by Magnetoman

Originally Posted by Zombie
I have the typical "guy" habit of glancing at the directions, and jumping in the deep end.
Through at least their 20s most people think they are immortal



I'm sitting here laughing even tho your advice is worth more than it's weight in gold.
The reason I'm laughing is my user name.
It's not just a user name, it is the nick name I have worn for 40 years. My mother actually coined the name (when I was 16) due to the number of times I should have been finished... Some things never change.


Originally Posted by johnm


Yes MM has probably got a reasonable working knowledge of chemistry. :-) He was outed on another thread so you can make a call on the quality of his engineering (and advice) from this !

http://www.optics.arizona.edu/research/faculty/profile/charles-m-falco



Ummmm... yeah. You got me there. Nice!

If I ever need to synthesize some Methionylthreonylthreonylglutaminylarginyltyrosylglutamylserylleucylphenylalanylalanylglutaminylleuc yllysylglutamylarginyllysylglutamylglycylalanylphenylalanylvalylprolylphenylalanylvalylthreonylleucylgl ycylaspartylprolylglycylisoleucylglutamylglutaminylserylleucyllysylisoleucylaspartylthreonylleucylisoleu cylglutamylalanylglycylalanylaspartylalanylleucylglutamylleucylglycylisoleucylprolylphenylalanylseryla spartylprolylleucylalanylaspartylglycylprolylthreonylisoleucylglutaminylasparaginylalanylthreonylleucyl arginylalanylphenylalanylalanylalanylglycylvalylthreonylprolylalanylglutaminylcysteinylphenylalanylglu tamylmethionylleucylalanylleucylisoleucylarginylglutaminyllysylhistidylprolylthreonylisoleucylprolylisol eucylglycylleucylleucylmethionyltyrosylalanylasparaginylleucylvalylphenylalanylasparaginyllysylglycyli soleucylaspartylglutamylphenylalanyltyrosylalanylglutaminylcysteinylglutamyllysylvalylglycylvalylaspa 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Posted By: BrizzoBrit

Re: 1957 BSA Spitfire Scrambler - 05/29/15 9:00 pm

So, do you want that glycosylated or not (sorry off topic, but couldn't resist).


But on brightening, once you've stripped the Al2O3 how do you prevent corrosion? I have lots of ally items that have been blasted sitting around around that have developed a nice white mildewy film of oxide.
Posted By: Zombie

Re: 1957 BSA Spitfire Scrambler - 05/30/15 12:26 am

I prefer my Titin on the rocks, please.

I gave up on shiny aluminium years ago. I'd rather ride my beater, than beat my rider.

The only thing I found that worked to any degree was pure silicone spray, and a rag. I'm sure there is a wealth of knowledge here on shiny aluminium, and maintenance. That's not my cup of tea.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 05/30/15 1:03 pm

Originally Posted by BrizzoBrit
once you've stripped the Al2O3 how do you prevent corrosion? I have lots of ally items that have been blasted sitting around around that have developed a nice white mildewy film of oxide.
Most people only have one choice to keep that white powdery corrosion from forming, but you have two. The first is to move inland from Brisbane because the salt in the air is corroding your aluminum. However, if you ignore that advice, choice number two is to wax the surface. After you've removed the oxide, clean the surface to remove any residual NaCl contamination, apply wax, and continue to enjoy those sea breezes. A smooth, transparent aluminum oxide film will grow to protect the Al and as long as the surface remains protected by the wax salt won't cause corrosion and dirt and oil can't embed itself in the oxide to turn it dull and grey again.

Interestingly, a related chemical reaction of Al and Cl is responsible for the death of Lucas magneto condensers. As a little of the chlorinated naphthalene wax used as the dielectric in those condensers starts to break down it releases HCl which then attacks the Al plates of the condenser releasing AlCl3. The aluminum chloride released from the corroding plates then attacks the wax to release even more HCl, which then etches even more Al, and the death spiral accelerates. Unfortunately, moving out of Brisbane won't help with your corroding capacitors. But, at least you don't have to worry about accidentally using chlorinated naphthalene wax on your cases because that stuff was banned years ago because it's a PCB.

I have yet to solve my HF problem. Several on-line suppliers have it at reasonable prices, but the problem is the Hazmat fee that UPS charges for transporting it is more than the cost of the HF. I didn't have much time this week to check with other possible local suppliers so I still have hope I can find someone in town who has it in less than 55-gal. drums.
Posted By: BrizzoBrit

Re: 1957 BSA Spitfire Scrambler - 05/31/15 8:00 am

Thanks MM

I rather like the 'coastal' location. But hadn't figured on salt in the air where I am several kilometers from the the ocean. Good point.


Wax is a reasonable solution. Not a big fan of super-polished everything, but do like to keep the ally in good trim even if not super polished. I found auto wax works pretty well for the polished covers, but does need redoing frequently if you want to be particular about this. I think once you get to the 'suitably-oxidised' (small protective film of oxide) and you dont polish too frequently it all seems to maintain itself pretty well really.

BB
Posted By: Tasman

Re: 1957 BSA Spitfire Scrambler - 05/31/15 8:58 am

Use wax if you wish. I live less than half a mile from the docks and therefore salt water but I have no problems with oxidisation. I simply rely on the oil leaks provided by the factory and just wipe down with an oily rag once every few weeks.

Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 06/04/15 1:01 pm

Been experimenting with Phosphoric acid bath, heated to approx 35C by a fish aquarium heater.

This brakeplate was dirty and badly oxidised and I first put it in a dishwasher and got all the dirt off but the oxidation was untouched. Next I put it into the phosphoric acid bath and left it for 2 hrs, it was fizzing as I took it out and had gone dark ie was covered in Aluminium Phosphate, I used a nylon scouring pad and rubbed some of this off but this left a residue. Experimenting with carb cleaner I found I could loosen the residues hold and remove it. The result is

[Linked Image]

You can see the full sized image here

s135.photobucket.com/user/kommando828/media/IMG_20150604_160914.jpg.html
Posted By: Dave - NV

Re: 1957 BSA Spitfire Scrambler - 06/04/15 3:46 pm

Slightly off the subject, but my question involves cleaning aluminum pistons by soaking in the popular/common 'Berryman Chem-Dip' carb cleaner.

For some years I had soaked pistons in the stuff to soften/remove the carbon and poured a bit in combustion chamber upside down on the bench. I also soaked pieces prior to sending them off to the cad plater.
However for the last few years I noticed the cleaning effect had worsened.
Suspecting the solution had weakened due to age I bought a fresh gallon can of Berrymans hoping for more effective cleaning. Nope, the soaked piston was still poorly cleaned. I suspect that 'safety' fears have changed the formula. I do remember in years past not to leave alu parts in the cleaner too long ie overnight, as the surface would blacken. This suggests an acid was in the cleaner??

Now after that spiel ... What additive could I add to the carb cleaner to improve it's effectiveness with reasonable safety? BTW, I always wear rubber gloves when working with chemicals.
Posted By: Zombie

Re: 1957 BSA Spitfire Scrambler - 06/04/15 6:04 pm

I use chem dip regularly. Like you I have found that it went from a two hour dip time to several days.

I check the parts at 2, 3, 4 days of dipping. I even found a float bowl that was in there for 2 weeks, and it was clean / not blackened.

If you want to use Chem Dip, just be prepared to leave the parts for several days. LOL... Gloves are a MUST! That stuff stinks!

The EASIEST way I have found to remove Al oxide is w/ a pressure washer, using a 50/50 mix of acetic acid (white vinegar) and water.
Screw the part in question to a piece of plywood, and have at it.
If you have a soda blaster or a media blast cabinet it is easy to convert back, and forth. Just replace the media w/ water/acid mix.

IF you don't have this sort of set up... Kleen Strip (paint stripper in a spray can) It works!
http://www.kleanstrip.com/product/premium-stripper-aerosol

MSDS
http://www.kleanstrip.com/uploads/documents/ESR72_SDS-4100B.1.pdf

Dichloromethane {Methylene chloride; R-30;
Freon 30}
70.0 -95.0 % PA8050000
67-56-1 Methanol {Methyl alcohol; Carbinol; Wood
alcohol}
< 5.0 % PC1400000
127087-87-0 Poly(oxy-1,2-ethanediyl),.alpha.-(4-nonylphenyl)-.
omega.-hydroxy-,branched
< 5.0 % RB2451000
124-38-9 Carbon dioxide < 5.0 % FF6400000
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/06/15 12:00 pm

Originally Posted by kommando
Phosphoric acid bath ... dark ie was covered in Aluminium Phosphate, I used a nylon scouring pad and rubbed some of this off but this left a residue. Experimenting with carb cleaner I found I could loosen the residues hold and remove it. .
Thanks very much for posting this. However, it's to eliminate this extra labor that makes HF worth pursuing, for me at least. I was tied up with other things this past week so still haven't found the time to try to track down a local source. When I do get some in hand I'll post the results to compare with your tests.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 06/06/15 4:53 pm

Trying to do the same but without the HF as its not readily available in the UK, took another brakeplate and got the same dark grey result after the phosphoric acid but this time no scrubbing but straight into kerosene for 24 hrs and after a swill the phosphate was gone. Will try some more different chemicals during next week.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 06/07/15 9:34 am

I agree regarding Berryman's Chem Dip. They're DEFINITELY changed the formulation a few years ago. Cancer-causing fears, etc. The old formulation was NASTY in every way, but EFFECTIVE in what it was designed to do.

Pitiful stuff now.
Posted By: Zombie

Re: 1957 BSA Spitfire Scrambler - 06/07/15 10:27 am

Here's a youtube vid showing that kleen strip I mentioned... https://www.youtube.com/watch?v=uQMLVAkgdEk

There are a few more as well. Hope it helps.
Posted By: shel

Re: 1957 BSA Spitfire Scrambler - 06/07/15 10:31 am

Berrymans ain't what it used to be. remember when engine degreaser used to actually degrease engines?
Posted By: Rusty Goose

Re: 1957 BSA Spitfire Scrambler - 06/07/15 12:55 pm

I have no knowledge of chemestry, smarter folks than I can weigh in here. I have used Pinesol to soak nasty carbs and related items. That stuff is aggresive when mixed 3:1 with water. If left too long it leave the metal dark like other have described here. It really has done wonders on old Stomberg carbs from the E type Jags I work on, especially if it is done in an ultrasonic cleaner.
Posted By: Rusty Goose

Re: 1957 BSA Spitfire Scrambler - 06/07/15 12:56 pm

I have no knowledge of chemestry, smarter folks than I can weigh in here. I have used Pinesol to soak nasty carbs and related items. That stuff is aggresive when mixed 3:1 with water. If left too long it leave the metal dark like other have described here. It really has done wonders on old Stomberg carbs from the E type Jags I work on, especially if it is done in an ultrasonic cleaner.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/09/15 1:58 am

I'm not sure if it counts as work on the Spitfire, but I'll count it anyway. My latest advance (or time-wasting digression) was to install a jib crane that swings over my mill and lathe. A friend who is winding up his construction business to retire made it for me from a 7-1/2 ft. section of 4" steel I-beam and ball bearing hinges. We mounted it 8 ft. overhead this weekend and today I installed the trolley and an electric hoist with 900 lb. capacity (a chain hoist would have been perfectly fine but I'm into working lazier... er, I mean smarter, not harder). The mill can "only" handle 375 lbs. max. but, not that I ever will do it, in principle the lathe could turn an 11"-dia x 36" steel bar weighing ~950 lbs. I wanted a jib crane up to any conceivable task and this is it.

Anyway, I now could lift an entire A10 engine onto the mill or set of cylinders onto the lathe without breaking a sweat. Also, tooling like the angle vise for the mill (61 lbs.) I used for restoring the fins on the Spitfire's head, or 16" auxilliary head for the lathe (93 lbs.) that I used to wind my magneto magnetizer isn't as much fun to toss around as it used to be, and now I don't have to.

Back to the Spitfire. Or on to the next digression...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/19/15 1:43 am

Looking back to my posts of February and March of 2014, at that point I had restored the broken fins on the Spitfire's head but still had to deal with the fact a previous owner had polished the top fins making it look wrong. Lots of other things have kept me busy since then, mostly not Spitfire related, so I set the head aside and deliberately had not done anything with the worn valve guides, etc.

Setting it aside doesn't mean I haven't been thinking about the problem. Unfortunately, the only potential solution I had come up with to produce a credible cast texture involved programming a pulsed, high power fiber laser system to write the cast-like pattern in the metal. Seriously. Although this approach was quite promising, several problems had to be overcome before it could be implemented on something as large and heavy as the head. Because of this, I didn't want to start down that rabbit hole if it could be avoided.

Very recently the deus ex machina to get me out of this appeared in the form of BritTwit who had come across a Spitfire head in much better condition than mine and who offered it to me at a price only a fool would refuse. The only defect (which he had alerted me to) is a previous owner had drilled two small holes where someone would have attached springs to hold the exhaust pipes in place. This is shown in the next photograph:

[Linked Image]
Compared with the effort to restore the fins on my original head, eliminating these holes should be trivial. Having this new, essentially unmolested head takes this restoration a significant step forward. Thanks, BritTwit!

Having two heads to examine allows previous tentative conclusions to be confirmed. The casting number 67-1126 is the same as for the head used on 1956-57 Road Rockets (i.e. part no. 67-1125), but with a "-S" stamped after the raised casting number. This is on the bottom of the inlet tracts of the old (upper) and new (lower) heads in the next composite:

[Linked Image]
Bottom of the inlet tracts of the old (upper) and new (lower) heads.

The difference this "-S" designates is the size of the inlet valve, which is larger than the one on Road Rockets. As I wrote a year ago, this means my Spitfire was the very first "Big Valve" BSA, produced six months before the company introduced this term in their marketing for the 1958 season.

One other set of numbers is on the head, stamped vertically near the inlet. They're clearer on the new head which is the one shown in the next photograph.

[Linked Image]

As can be seen it has the codes 'CG 54' and '58A27FX' at the left side of the inlet tract. My old head has the code 'CG 82' (or possibly 'CG 22') on the right side of the inlet tract, but no sign of any additional stamping.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 08/12/15 10:27 pm

I decided about 3-4 months ago that I had too many almost-running bikes and I needed to spend the time to take away the "almost." As a result the Spitfire was on the back burner while I turned my attention to these other bikes. I've now largely accomplished that, although with something still on order for one of them, so I'm beginning to spend more time with the Spitfire again.

Shortly I'll be to the point where I will need to pull the Spitfire's engine so I decided to make a jig for that purpose. I wanted to make it flexible enough that I could use it with my engine hoist to easily get the engine in and out of the frame with the head on or off (and without scratching the paint on the frame), and general purpose enough that I could easily modify it to work with Gold Stars as well. Even Triumphs and Matchlesses. With that in mind it had to be "C" shaped and tall enough to place the lifting point above the top frame tube, with the lifting point somewhat adjustable so I could place it directly over the center of gravity.

I decided to base it on three pieces of aluminum from my stock that were in the form of an "L", a "U" and a box. I first machined one leg off the "U" and drilled four holes for attaching to the engine. I easily could have bolted the pieces together to do the job but what's the point of owning a welder if you don't use it to weld?

The problem I faced was when I bought my welder I decided on a size that I was sure would handle 99% of anything I'd ever need it for, and this job was in the 1%. Basically, a 200 Amp welder is good for Al up to 1/4" thick but some of what I needed to weld was 3/8" and the "L" piece tapered from 1/4" up to 3/4" just before it made the 90-deg. turn.

Although I didn't expect to be able to weld all of it, this was a good opportunity to see what my welder could do if pushed hard. So, I welded what I could. But, as expected, it wasn't up to the full task, barely able to slightly melt the top surface of the thicker pieces so I could make tacks. I have full use of a 350 Amp machine so I could have used that to finish, but instead I used this as an excuse to buy the bottle of helium that's been on my list for over a year. Helium added to the argon can "significantly" improve the ability to weld thicker sections of aluminum, but I didn't know by how much that would be in practice with my own machine.

It is written in many places that anything more than 20% He affects the "arc stability." But, more He makes for hotter welds and thus thicker sections. So, my choices were to buy a 100% He bottle and make a manifold to mix it with my 100% Ar in any ratio I wanted, or to buy a premix bottle. But, what percentage He given the "arc stability" issue? I decided on 50/50 since I could always dilute it using a manifold if that turned out to be necessary. But, when I tried it I discovered that with a modern inverter TIG welder the warnings about "arc stability" are like owning a modern car and being worried about warnings to change a car's points and condenser.

Anyway, adding He to the mix was like adding nitromethane to gasoline. The photo shows the engine installation/removal jig I made from these three pieces of scrap Al:

[Linked Image]

As can be seen, there are four holes positioned for attaching to the cylinders with through studs with the head on or off, four half-circles to clear the guides if the head is on, and room to add more holes where necessary for a Gold Star or other engine. Ignore the tapped hole and notch from the corner of the bottom piece, which were there when I started.

I made a slot running 1-1/2" either side of the center line of the cylinders to allow for fine tuning the lifting eye to be directly over the left-right center of gravity but am relying on the basic symmetry of the engine, and location of the heavy flywheels, to take care of the less critical front-aft balance.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/28/15 5:25 pm

About 15 months ago our offer on a new house was accepted so I immediately started packing up everything in the garage in preparation for the upcoming move. The gearbox was one of the first things to be packed. I decided it's time to return to it and get it finished.

I note that the 5th edition of 'The Gold Star Buyer's Companion' contains a very detailed description with a number of images that allow one to distinguish between an RRT2 and the other gearboxes, including images of the speedometer gears at the end of the layshaft and in the outer housing:

https://www.createspace.com/5757916

In what follows in the next few posts I'll refer to some of that information that is directly applicable here, and also to the BSA chart that shows the components of the various pre-unit gearboxes that can be found earlier in this thread at:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=534678#Post534678

Having unpacked the box and spread everything out in trays I decided the next issue to deal with is the unacceptable amount of play in the actuating arm. As can be seen in the next photograph the up-down motion of the end of the arm is nearly 0.06".

[Linked Image]

It also can be seen that the arm is somewhat bent. It turns out I have a half-dozen complete and 4-5 incomplete gearboxes from which I could take an outer cover. However, I don't want to cannibalize a good gearbox, and the ones that are apart each have issues of their own that would have to be dealt with. For example, although the cover shown in the next photo has an actuating arm that is straight and with minimal play, it can be seen that a chunk of the casting is missing where the outboard end of the speedometer gear goes:

[Linked Image]

So, in the interest of making this restoration thread as detailed as possible, and against anyone's better judgment, instead of simply swapping covers I decided to repair the current one by installing and reaming a sleeve (which is a lot more work than is implied by this one-sentence description). Since, no matter what, I want an actuating arm that is straight I removed the one from the housing shown in the previous photograph. The next photograph shows the inner end of this assembly after I had removed the cotter pin and loosened the nut enough to spread the components apart.

[Linked Image]

Since the part of this assembly that pushes against the clutch rod is located on the shaft by splines it is necessary to know the correct orientation so it can be properly reassembled. As the two views in the next composite show the flat faces of the bottom piece are parallel to the actuating arm. This makes its motion against the clutch rod perpendicular to that of the actuating arm, which is what is needed to transmit maximum force and provide maximum movement.

[Linked Image]

The next photograph shows four of the five pieces of this assembly (missing is the cotter pin) after removal from the cover. After removing the nut and washer the other piece is a slip fit over the splines of the shaft.

[Linked Image]

The diameter of the portion of the assembly that rotates in the housing is 0.435" which means the hole in the housing is 7/16" (0.4375"). However, so far I've only made one quick measurement of this one shaft so I don't know how much it might be worn and, in any case, I might decide on a bit less clearance than the 0.0025 this implies.

All that remains to be done is to accurately align the housing in the mill and bore the hole to receive an Al sleeve that itself will have to be reamed after being pressed into place (and, possibly, tack welded).

[to be continued]
Posted By: Dave - NV

Re: 1957 BSA Spitfire Scrambler - 09/28/15 6:02 pm

MM ... For several years I've been rebuilding BSA tranny outer covers and have done ~ 35 boxes with Never a complaint or 'come back'. I have the unique dedicated fixtures, knowledge
and tooling required. The most common need is replacing the worn shifter and kicker shaft bushings with modern materials that from original seeped oil. Then machining a counter bore into the cover and pressing in tiny steel body lip seals that are nicely out of sight. Stop the drool!

But your issue with the clutch arm shaft caught my attention and is why I'm commenting. This shaft pivots directly in the alu cover with very little lube as most riders never grease it and the hole is commonly worn oversize and oval. Part of the rebuilding items I do is jigging up and boring the clutch arm bore in the cover. Then I press in a pair of 'no lube required', thin wall lead/tin coated steel bushings. One above and the other just below the grease zerk port. Works great. I like that.

I also remove the hollow dowels and flatten the cover's face with emery cloth on plate glass. And then of course replacing the dowels with new items.

I don't 'need' the business or the money, but I charge $105 + return postage for this work on clean covers, that are hopefully polished out before I do the job.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 09/29/15 10:28 am

Dave, the modifications you describe certainly would make the gearbox better than it was when it left the factory. Unfortunately, I'm restoring this Spitfire in a way I know you disapprove of, i.e. as close as possible to as it was when it left the factory. As I wrote in the first paragraph of the first post in this thread, this is "an approach to restoring a motorcycle that not everyone will want to copy."

If this Spitfire were serial #2 rather than #1 I would be rebuilding it incorporating sensible modifications like you described rather than restoring it. Or, more likely, I wouldn't be rebuilding it at all given the decrepit state and incompleteness when I got it.

I have other motorcycles to ride hard and put up wet. This one is more of a Zen exercise. By setting the goal posts where I set them, and farming out work only where I have no reasonable alternative (e.g. cadmium plating), it pushes me toward learning the limits of what is possible for me to do. Otherwise, it would be all too easy to allow myself to take easier shortcuts (that's not to say the particular gearbox modifications you describe would be any easier than what I'm doing with this cover) such as use the perfectly fine ASCT I've had for 20 years rather than rebuild this SCT2, buy a new Amal (or Mikuni) rather than search years for and then sleeve at considerable effort the proper Amal 379/89, buy one of any number of perfectly functional A10 heads that regularly appear on eBay rather than reconstruct fins on the proper 67-1127 head, etc. So, please bear with me even though this isn't how you would approach this.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/05/15 11:31 am

To sleeve the hole for the clutch actuator in the outer cover I first made a jig from a 1/2" Al plate whose bottom edge I faced to be flat. While aligning the hole in the cover to be vertical using a 7/16" steel rod held in a collet in the mill I clamped the cover to the plate, marked the position of the four holes with a transfer punch, and then drilled and tapped those holes 5/16"-18. This means any cover clamped to that plate always will have the correct vertical orientation when held in the vise, although each time the jig is used X and Y will have to be located (which isn't difficult). After bolting the cover to the plate it was easy to position the hole directly under the spindle using the same 7/16" rod, as is shown in the next photograph.

[Linked Image]

Although it can't be seen from this photograph I left a ~1/4" gap between the bottom of the cover and the top of the vise when the jig is fully seated to allow for individual variations in future cases (not that I have any plans to do this again, but you never know...).

One option would be to press an Al rod into place in the cover and then drill and ream it to the correct size for the actuator. Instead, I made the 1-1/2" long Al piece in the lathe.

[Linked Image]

By making the Al piece first I could be sure the hole hadn't wandered off center when I drilled it. The sleeve eventually would have a 7/16" ID hole for the actuator but I drilled it 1/32" under size in the lathe since I would ream once pressed into place in the cover.

I used 1/2" nominal dia. 6061-T6511 Al rod to make the sleeve which after polishing the surface a little using Scotchbrite ended up just over 0.500" OD. One set of reamers I have has 0.001" over and undersize reamers in each size so I next installed the undersize 1/2" reamer in the mill and reamed the cover as shown in the next photograph.

[Linked Image]

A test fitting showed the Al sleeve had the right amount of interference for a press fit. I pushed it in a short distance using the mill but then unbolted the cover from the jig (leaving the jig in place in the vise) and used the shop press to push it in the rest of the way. The sleeve needs to be just over 1.5" long but I made it approx. 1.75". The following photograph shows it after the sleeve had been pressed all the way in until stopped by the steel support bar so ~1/4" is protruding from the top.

[Linked Image]

I bolted the cover back on the jig and reamed the hole with a 0.001" undersize 7/16" reamer. If the fit turned out to be too tight I could easily make the hole a little larger, but making a too-large hole smaller isn't quite as easy. After reaming the hole I removed the ~1/4" that was protruding from the top of the cover using a 17/32" drill bit, removed the jig from the vise, laid it flat, and drilled the hole for the grease.

The next photograph shows the final result, with the actuator held out of the way so the top of the sleeve is visible. Actually, nearly invisible, and the fit is perfect. The actuator rotates freely with no drag and with no perceptible up-down motion on the end of the arm.

[Linked Image]

The cover still needs new steel sleeves for the kickstarter and gear shift shafts. But, before installing those I'll want to polish the cover to return it to the state it had when it left the factory. Which is a problem. What passes for "restored" these days are covers polished to a chrome-like finish unlike anything I remember having seen in dealerships back in the 1960s. My goal is "restored" not "over-restored" so I have to determine how to accomplish that with the polish.

I haven't yet closely examined the speedometer gear so that remains to be done, as does installing new bearings in the two other housings.

[gearbox restoration to be continued]
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 10/05/15 12:29 pm

Been scratching my head on the polishing question, any photo's from the day are catalogue, Earles Court show bikes or factory prepared test bikes so probably not showroom examples. An NOS cover properly preserved with good packaging is the only suggestion I can come up with.
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 10/05/15 2:48 pm

I bought a nos rocker cover for the A65, the polished parts were pretty well polished, maybe pre units were different???
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/05/15 3:23 pm

Kommando and Allan, thanks for your responses. As I wrote yesterday in an exchange with John Healy in the Triumph Forum, I've made progress towards a definitive answer to the question of polishing thanks to the eleven A10-type gearbox covers I have. Although before coming to a definite conclusion I want to look at a few more covers with my metallurgical microscope, so far what I wrote in the Triumph Forum seems to be the case:

"Examining places where a polishing mop wouldn't have easily reached when being done quickly at the factory (e.g. around the protrusion for the clutch actuator, near the oil drain hole at the back, the speedometer exit at the front, ...), sharp casting marks and a rough sand-cast texture like on the crankcases can be seen on all of them.

From looking at these covers it is pretty clear that the workers held the covers against the buffing wheel long enough to eliminate the sand cast texture in the large open areas, but spent very little time on other areas. I'm going to guess that two steps were used in the polishing: a first fairly coarse one to quickly eliminate the sand cast texture in the large areas, followed by a second fine polish to shine those large areas and to brighten the others even while leaving them relatively coarse."


Anthropologists can infer considerable information about the practices of extinct peoples from the tools and artifacts they left behind. I'll post photographs and micrographs in the next installment that show what I've been able to deduce about the polishing rituals of the primitive species Pithecanthropus Birminghamus. Oddly, although it appears they had opposable thumbs, preliminary analysis seems to indicate some of them must have had ten thumbs...
Posted By: Allan Gill

Re: 1957 BSA Spitfire Scrambler - 10/05/15 3:37 pm

That describes my rocker cover exactly, the fiddley finned area was smooth but left like a satin finish, the larger flat areas were highly polished, I buffed my unit and polished the complete unit whilst I was at it. It's actually harder to keep some parts unpolished than some may think, which then pushes you to polish in detail the whole piece.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/12/15 12:14 pm

It turns out I have at least eleven A10-type gearbox covers. The covers are in different conditions and have found their way to me from different sources over the past few decades so are a reasonably random selection. Only one of them (on my BB Gold Star) appears to have been polished in modern times so they seem to be like they were when they left the factory, although with uniform grey oxide layers and different amounts of "modern" scrapes and scratches

The next figure is a macro photograph of the region between the hole for the clutch actuating lever and the grease fitting on a representative cover.

[Linked Image]

As can be seen this region of the cover has a rough as-cast texture, and it is basically the same on the other nine covers so it isn't due to corrosion. A slightly larger area of the same cover is shown in the next composite with the area of rough texture highlighted in yellow on the right.

[Linked Image]

Other areas of rough texture, where a polishing mop wouldn't have easily reached when being done quickly at the factory, are shown in the next few photographs.

[Linked Image]

[Linked Image]

[Linked Image]

Sharp features from the mold and a rough sand-cast texture like on the crankcases are found in each of these areas on ten of the eleven covers (the eleventh being the one on my BB Gold Star).

After examining these ten covers my conclusion is a worker manipulated each of them against a buffing wheel charged with a coarse abrasive long enough to eliminate the sand cast texture in the large open areas, but spent little or no time with that wheel on other areas and instead moved on to a fine wheel. The most plausible explanation for the appearance of these covers is that two steps were used in the polishing: a fairly coarse one to quickly eliminate the sand cast texture in the large areas, followed by a second fine abrasive to shine those large areas and to brighten the others even while leaving them relatively coarse. It would have been more efficient if the same worker did both steps on a dual-wheel buffer since if he noticed in the second step that he had missed a spot with the coarse wheel he could quickly "hit" that spot again and then return to the fine wheel.

The two-step process described above would produce a semi-reflective surface only on the large areas. However, the rough portions (e.g. near the clutch actuator) still would have been shiny. Remember, that Al foil is shiny and reflective when on the roll. Although after it has been used to wrap something it is no longer mirror-like due to the many wrinkles and folds, it still is shiny. Similarly, the rough as-cast areas would have been shiny after polishing with the fine abrasive.

Even though the covers in my "collection" are now a dull grey (rather than a bright silver), the oxide coating responsible for the loss of reflectivity of Al, unlike Fe, is uniform and quite thin, making it possible to determine how smooth the original finish was when the covers left the factory ~60 years ago. I examined three of these covers with an inverted metallurgical microscope (necessary, because the covers are too thick for the stage of a standard microscope).

Because there are no flat surfaces on the cover, and because of the shallow depth of field at high magnification, it would take a bit of work to create a micrograph at high magnification. Rather than do that, the next micrograph is at a fairly low magnification, although still covering a total horizontal distance of only 0.9mm. It will appear on your screen at a magnification of ~250x

[Linked Image]

I actually can see the features at a 20x higher magnification than this one but only by racking back and forth through focus because of the very shallow depth of field. Anyway, between the scratches, there are "large" (on a microscopic scale) ~20x20 micron regions that are flat to better than 1 micrometer. Because the surface consists of roughly equal amounts of flat and scratched areas it would have had significant specular and diffuse reflection when it left the factory, i.e. it wouldn't have been like either a mirror or a frosted surface, but would have had elements of both in the reflected light.

The scratches that are apparent in the above micrograph are ~5 microns wide, while at higher magnification it's possible to see a second type that are ~1 micron wide. This means the "polished" areas of the cover saw at least two grades of abrasive: a coarse 5 micron (~800 grit) polish to remove the casting texture followed by a fine ~1 micron (~2000 grit). There might have been an initial polish with an even coarser grit to remove the casting marks even more rapidly but, if so, traces of it were removed by the finer abrasives in the areas I examined.

The conclusion from all of this is that to reproduce the factory finish requires first removing any deep, modern scratches from the polished surfaces. Once this is done, the final two steps in polishing should be 5 micron and then 1 micron abrasives while taking care not to polish for too long or be too aggressive in the as-cast regions so as not to remove any of the texture or sharp features. Spending anything longer than a minute each on the buffing wheels during these last two steps would result in an over-polished surface.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/19/15 10:11 pm

Although not directly related to the Spitfire, I'm going to count some work I did this weekend anyway because it likely will be used for the Spitfire when the time comes.

In May I bought a used set of DocZ starting rollers from the estate of someone in town. The rollers only had one motor on them which appears to be how it had been configured when the guy bought them originally. However, I found that the one motor was sufficient to start all my bikes without problem so there was no reason to add a second motor. Except, that blank mounting bracket kept staring at me every time I walked past it...

No longer able to ignore the empty bracket, at the end of July I emailed the guy who makes them, Art Zimmerman, to ask the price of the mating gear required for the shaft with the missing motor. Has soon as I heard from him I immediately mailed him a check and the gear arrived six weeks later. Meanwhile, I bought a rebuilt starter motor on eBay. However, since there was no need whatever to have that second motor on the rollers I put everything aside. Until I couldn't stand it any longer. This weekend installed it. Although it appears one only has to slip a gear onto the shaft and attach the motor, nothing ever is quite that simple so several hours of work were required just to do this. I also used this opportunity to make two modifications to the rollers, which took additional time beyond just adding the second motor.

DocZ sells rollers in two configurations, one with ramps at both ends so you can push a bike up and over it until the rear wheel is in position, and the other only with an "exit" ramp so you push a bike backwards onto it, with a hard stop to keep a bike from going too far if the pushing is too energetic. So, one modification I made was to remove the "entrance" ramp and bend a 10"x10" piece of 1/8" steel into shape to serve as the hard stop. I painted the steel with an etching primer to keep it from rusting, and with not-quite-matching yellow paint I happened to have. This is shown in the photograph.

[Linked Image]

A dolly can be used to move the rollers, which would be handy if moving fairly long distances or over rough terrain. However, when not being used in the garage I only need to move the unit ~10 ft. over concrete to start a bike outside. The rollers have wheels at one end but lifting the unit high enough from the other end for those wheels to touch ground and then moving it while bent over is quite awkward and cries out for a handle. So, the second modification I made was to TIG weld a piece of scrap Al to the side opposite the wheels and bore it to a depth of 1-1/4" to use with a spare jack handle. I first turned~0.015" off one end of the handle to make the "round" handle actually round, measured its diameter, then drilled a hole a few thou. larger than that in the Al. At first I thought I would need to do this at an angle but after propping the DocZ up at the necessary angle for the wheels to touch the ground I saw that drilling straight on would result in the end of the handle being the right height for moving when my arm was fully extended, i.e. so the strain on my arm would be minimum. Note also that I offset the handle toward the motors to place it very roughly at the left/right center of gravity to keep the rollers from tipping when being moved.

For completeness I'll mention a third modification I made several months ago. That was to glue 1/8" rubber to all of the bottom surfaces to keep the unit from sliding on the smooth epoxy floor of the garage when loading a bike onto it. Also, as can be seen in the photograph, I have Walmart's finest 810 CCA battery sitting on a Harbor Freight furniture mover to make it almost effortless to move the necessary 10 ft. as well.

Now all I need to do is finish rebuilding the Spitfire because the modified DocZ is ready to start it.

Addendum:
The photograph shows additional modifications I made to the starting rollers to make it better for my uses:

[Linked Image]

For times when I need the rollers for sorting out problems on a bike, not just to start it, I made a 34"-wide cross-bar from 2"x2"x1/4" aluminum angle stock into which I milled slots to give greater clearance for tires. This way I can "permanently" leave a bike on the rollers between sessions by using tie-downs (which have to be loosened when actually using the rollers because the tire wanders to one side or the other if the bike isn't perfectly vertical). The cross-bar quickly attaches to 1/4" bolts in existing holes in the Solo frame whenever needed. By making a more elaborate cross bar I could have mounted it further back and not needed to mill the slots, but it was a trade-off between spending time doing that or quickly milling the slots. Milling won.

Also can be seen are the ~5"-tall platforms I made from 2"x6" lumber that give me a more stable position rather than standing on my tip-toes when using the rollers. While the latter is OK when only using them to start a bike outside, the platforms help a lot when working in cramped quarters.

Not specifically a roller modification, the exhaust tubing lets me run a bike inside the garage for as long as I need without asphyxiating myself or having to breathe exhaust fumes the rest of the day. The tubing that slips over the exhaust pipe is a high temperature silicone rubber and the larger dia. corrugated tubing is made for just this purpose. If I'm going to run a bike for more than a minute or so I aim a portable fan at the engine.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 10/20/15 9:06 am

You should have gone down to AutoZone and bought one of their lifetime warranty starters, a much better deal.

Anyway, nice rig. I have 2 spare motors for mine (that I'll probably never use) that I bought in haste because the ones I ordered online hadn't yet arrived by the time I was rolling to Bonneville in 2008.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 10/20/15 2:09 pm

Originally Posted by GrandPaul
You should have gone down to AutoZone and bought one of their lifetime warranty starters, a much better deal.
I don't remember what I found when I looked into it at the time, but my NAPA-remanufactured motor cost only $43 delivered to my house. A quick look on Autozone's web site just now didn't turn up any remanufactured motors, but it's hard to imagine with core charge and tax anyone could sell such a motor much cheaper than that. Also, I didn't have to make a trip to an auto parts store to deal with someone who insisted on knowing what year and model Ford truck the motor was for in order to look it up, plus a second trip if he had to order it.

As for lifetime warranty, if the motor I bought on eBay would fail after only a decade of starting a large truck twice daily, it should last "forever" for my use on the DocZ, i.e. well past my own best-by date. My hope is the DocZ itself significantly extends that best-by date by saving wear and tear on my body.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/01/15 12:45 am

Safety Warning: Very briefly, this post makes use of hydrofluoric acid so goggles and gloves are essential because splashed acid is a real possibility. Before anyone uses HF they need to read and follow all safety instructions.

After the DocZ digression it's back to the gearbox. I finally got a gallon of 20% hydrofluoric acid which should be enough for this purpose. However, HF needs to be tested to see if it removes the grey oxide from the cast Al without causing any problems. The next photograph shows the very oxidized and much abused outer cover I found in my collection that I used for this test.

[Linked Image]

The above photograph shows the cover after the test. The top image of the next composite shows the area immediately under the oval access hole before I started the test.

[Linked Image]

I first used a paper towel to wipe the area directly under the oval hole, the result of which is shown in the center image of the above composite. I wiped it fairly hard several times but it still was just a paper towel so only loosely adhering material was removed. After doing this I used a disposable soldering "acid brush" to brush 20% HF onto the area immediately below the hole. I left the HF in place for about one minute before rinsing the cover. The result is shown in the bottom image in the above composite. As can be seen in this composite, and in the first photograph, the HF removed the grey oxide.

The next composite shows that the HF acid removed the oxide but left the texture of the Al untouched. This time from left to right is a higher magnification image of a region only ~5mm wide of: the original case, after rubbing with the paper towel, and after treatment with the HF.

[Linked Image]

At this point I'm ready to deal with the cosmetics of the cases. First, though, bearings, bushings, and the speedometer gear have to be removed.
Posted By: triton thrasher

Re: 1957 BSA Spitfire Scrambler - 11/01/15 5:29 am

Originally Posted by Magnetoman
Safety Warning: Very briefly, this post makes use of hydrofluoric acid so goggles and gloves are essential because splashed acid is a real possibility. Before anyone uses HF they need to read and follow all safety instructions.



Goggles and gloves are not enough, frankly.

The safety instruction is take nothing to do with hydrofluoric acid.

I know you're not advising us all to set up pickling baths of aqueous HF in our kitchens but just in case anyone thought you were...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/01/15 11:15 am

Originally Posted by triton thrasher
The safety instruction is take nothing to do with hydrofluoric acid.
It's better to be overly cautious than too cavalier in dealing with HF so I don't disagree with the tone of what you expressed. People who can't work slowly and carefully when it's called for should not use HF. But, when proper safety procedures are followed the hazard is reduced to an acceptable level as evidenced by the fact HF is widely used by workers in the semiconductor industry.

I and several dozen people working closely with me have regularly used HF over the past three decades without incident thus far. During that time one of these people who wasn't wearing goggles even though she knew better splashed acetone in her eyes resulting in a 911 call and a trip to the Emergency Room. Luckily, she was fine. She would not have been fine had it been battery acid (H2SO4), swimming pool acid (HCl), nitric acid or HF, all of which the same people also have regularly worked with over the same period and all of which require using appropriate safety procedures.

When posting here about batteries people seldom include cautions about wearing goggles or a face mask even though the consequences of battery acid in the eyes is every bit as serious as HF in the eyes. That said, anyone who doesn't know what are the appropriate safety procedures to follow should not use HF, and anyone who thinks they know should still take the time to review them to be sure. And, as the acetone incident illustrates, knowing the procedures only counts if you follow them.
Posted By: triton thrasher

Re: 1957 BSA Spitfire Scrambler - 11/01/15 1:31 pm

I still sometimes work in a building with windows frosted by adventitous HF.

Although I wouldn't bring it onto premises just to clean an old casting and I wouldn't rely on personal protective equipment (nor slow careful work) to control the hazard, I'm delighted for people who know what they're doing, to use the stuff.


All sorts of people read the forum, though!
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/01/15 4:40 pm

Originally Posted by triton thrasher
I'm delighted for people who know what they're doing, to use the stuff.
All sorts of people read the forum, though!
Fair enough. Everyone reading this thread has been cautioned to treat HF with great respect, and that they need to take appropriate steps if they are to use this chemical without unnecessary risk to themselves or those around them. Ignore this warning at your peril.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/26/15 4:33 pm

Because of travels I have yet to find the time to return to the gearbox. But, I have a request, a question, and a semi-relevant update.

Going way back almost to pre-history, the bottom photograph in the following post shows the Spitfire engine came to me with a tachometer drive in the timing cover:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=504903#Post504903

However, the photograph used in the original press release, at the top of the same post, upon which I've based several restoration decisions shows the timing cover is machined for a tachometer drive but that it is covered by a blank plate. I don't have a plate to use on my engine so this is a loose end I'd like to tie up. So, my request is that if someone has one of those plates gathering dust please send me a PM because I would like to buy it. And, my question is, if you have one you believe to be in original condition, even if you don't want to sell it could you let me know what material it is made of and how thick it is (and, if it's steel, is it Cd plated)?

Turning to the update, which I'm counting as relevant-ish because I'll need it when the Spitfire nears completion, a problem I have is my roll-up garage doors only stop in the fully closed and fully open positions. They can't be tricked into stopping in any other position. What this means is if I start a motorcycle in the garage I have the choice of letting out all the A/C (summer) or heat (winter), or breathing exhaust fumes the rest of the day even if the bike runs for a very short time. And, even if the doors are open, the noise could (would) annoy the neighbors.

Because there are times when I'd like to run a bike for a few minutes after starting it in order to sort out issues, I recently purchased Dayco 63525 2-1/2" ID exhaust hose. The hose isn't cheap but I couldn't find any reasonable alternative so I bit the bullet. It's cleverly designed for the 11 ft. sections to mate, giving me a 22 ft. hose to run through the side door and several feet beyond.

As for connecting the hose to the bikes, I measured the OD of the outlets of all my motorcycles and found that adapters of four different diameters would take care of everything. Should I ever work on something not covered by these four sizes it would be easy enough to make an additional adapter. To avoid confusion (I hope) in what follows I'll only give the relevant pipe size. In the case of 2" pipe the ID is 2" but the fittings I used have an OD of 2-3/8". Where I need to connect to the 2-1/2" ID Dayco exhaust hose a few wraps of tape around the PVC pipe results in a snug fit without needing a hose clamp.

You will see that I made adapters from a mix of white PVC and black ABS fittings (because the hardware store didn't have everything I needed in only one of the materials). The fit of the various components together is tight enough that they don't need to be glued, otherwise compatibility would have required me to use epoxy. However, the tight fit gives me the flexibility to alter the configuration as needed so I don't plan to epoxy anything..

The next photograph shows the Dayco exhaust hose connected to a Gold Star via a PVC adapter and short length of 2" ID hose that came from a now-dead shop vaccum:


[Linked Image]

One end of the shop vac hose fits inside the 2" PVC pipe coupling, and a 6" length of PVC pipe is at the other end of the coupling over which the Dayco exhaust hose slips.

The next photograph shows the Dayco exhaust hose connected to a Ducati twin via being slipped over a 6" length of PVC pipe that fits into the "outlet" of the black ABS 'T'. Both "inlets" to the 'T' go to two 45-deg. fittings and then go to 2-1/2" ID Tygon tubing clamped to a 6" length of PVC. Conducting test assemblies in the aisle of the hardware store showed that the wider spread due to using 45-deg. fittings was perfect for the Ducatis and the Trident.

[Linked Image]

The final photograph shows 3" ID Tygon over one of the exhaust pipes of the Trident.

[Linked Image]
Other than the step-down adapters for this larger diameter Tygon the rest of the fittings are the ones in the previous photograph. This same 3" Tygon also fits over the odd shape of the silencer of my Matchless G80.

In addition to the ones shown, I also made adapters for 1-3/4" OD and 1-3/8" OD exhaust pipe outlets in the same way. Together, the adapters cover all the motorcycles I own so I can now tune to my heart's content in air conditioned comfort without filling the garage with blue smoke.
Posted By: tridentv

Re: 1957 BSA Spitfire Scrambler - 11/26/15 5:57 pm

Flip your garage door electrical panel breaker off when the door is in your need position.

Warren
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 11/26/15 8:56 pm

Originally Posted by tridentv
Flip your garage door electrical panel breaker off when the door is in your need position.


That's too easy.

It would be so much more fun to fabricate my own PC board with trigger and relay circuits to interrupt travel with a "clapper" system over-ride in case I pin myself with the moving door.
Posted By: TR6Ray

Re: 1957 BSA Spitfire Scrambler - 11/27/15 12:22 am

Magnetoman,

When I use the wall-mounted switch for my door opener, I can hit the button at any point while the door is traveling upward, and it will stop at that position. Hitting the button again will cause the door to close. I know that may not relate to your door control.

Even so, I wonder why you don't use an exhaust port. We always had these at the gas stations where I worked as a kid. That was in those ancient days when the back room of a "Service Station" was more than a milk, cigarette, and lottery ticket dispensary. A quick google search turns up different ones like THIS.

That would let you keep the door fully shut and just poke the hose out through the port.

Now, finally -- Yikes! I have cleaned off melted plastic more than once when my wife got the sole of her boot too close to the exhaust pipe. Are you really going to put those plastic adapters on your bikes like that?

Ray
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/27/15 11:14 am

Originally Posted by tridentv
Flip your garage door electrical panel breaker off when the door is in your need position.
It's not like I need to do this frequently, but circuit breakers aren't designed to survive thousands of cycles being used like a switch. I can remember at least two circuit breakers in my previous house that I had to replace after they had tripped only a few times (the house was ten years old when I bought it and I don't know the previous history of those circuit breakers).

In any case, the feng shui of my garage resulted in my lift and the DocZ rollers being side-by-side located one row of bikes deep into it (~10 ft.). That's where the semi-running bikes will located that this solution addresses. Because of this location, I've already established that even with both 100 sq.ft. roll up doors open and a fan running fumes rapidly fill the space where they linger for a long time. The fumes certainly are more diluted than if the doors were closed but still are way more concentrated than I care to breathe at this point in my life.

Originally Posted by TR6Ray
Yikes! I have cleaned off melted plastic more than once when my wife got the sole of her boot too close to the exhaust pipe. Are you really going to put those plastic adapters on your bikes like that?
This is certainly a valid concern. However, whatever plastic that Dayco uses for the hose it clearly can withstand being in direct contact with a car's exhaust pipe for extended periods so melting of it isn't a concern. The PVC and ABS fittings are rated for continuous use without pressure at 180 oF. Despite whatever temperature the exhaust gas has when it reaches these components they will be fine for this application.

The worry you quite rightly expressed is for the tubing that will be in direct contact with the metal at the end of the exhaust pipes. The clear tubing I selected is specified to have an operating range up to 165 oF at 10 psi, and is also suitable for sterilizing in an autoclave so it can survive multiple exposures to 250 oF for at least 15 minutes when it is unpressurized. Not shown is the tubing for the smallest size which is a silicone rubber rated for continuous use at 390 oF (it isn't available in larger sizes).

In a gas station, where I also worked during one carefree summer of my youth, cars ran for a long time (15 min.?) while setting the timing with a strobe, checking alternator output, messing with the carburetor, etc. However, even in those days when I was happy to breathe fumes I only had a bike running for maybe two minutes at the most when I was working on it inside a garage. Hey, they had Amals so being able to idle for 15 minutes was a mythical goal strived for, not something that was ever achieved ... Anyway, while the pipe near the head gets too hot to touch when a bike runs for two minutes, it is much cooler at the outlet.

Originally Posted by TR6Ray
I wonder why you don't use an exhaust port. We always had these at the gas stations where I worked as a kid.
I was aware of ports for this hose from my search for alternatives to the expensive Dayco but decided to wait to see how things worked out with the side door cracked open by the necessary ~3". Installing a port in the roll up doors isn't possible, and it would/will take quite a bit of time to punch a suitable hole through the metal side door to accept a port (the actual walls are cinder block so also not easy to punch a hole).

Remember, few of us are in business doing tune ups on multiple vehicles so it's not like the ~1-1/2 sq. ft. of cracked-open door ever would be leaking out AC/heat continuously all day. The solution I described is one for a home mechanic, but it would be unsuitable for a commercial establishment.
Posted By: quinten

Re: 1957 BSA Spitfire Scrambler - 11/27/15 8:51 pm


I may have missed it , or forgotten ,

But is your exhaust system powered with any vacuum boost ?

... A loose fitting vacuum/blower would less likely melt at the tailpie or mess with back pressure .

.it could be switched on automatically with a low psi pressure switch .
... AND As a bonus , be more complex and expensive .

.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/28/15 11:36 am

Originally Posted by quinten
is your exhaust system powered with any vacuum boost ?
... A loose fitting vacuum/blower would less likely melt at the tailpie or mess with back pressure .
An on-line calculator shows the pressure drop over the 22 ft. length of the hose for the exhaust gas flow rate from a 500cc engine at 500 rpm only would be ~5%. That is, the restriction of the hose is negligible, nearly the same as if it weren't there, so the additional back pressure will be equally negligible.

Originally Posted by quinten
... AND As a bonus , be more complex and expensive .
Yes, complex and expensive is always a bonus. The equivalent with tires is the better they are, the more expensive, and the faster they wear out.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/20/16 1:42 pm

Having way too many things going on in my life (which, overall, is a good thing) has slowed work on my Spitfire to a crawl, if not a full stop, over the past few months. My latest diversion is a friend's bitza ZB34/M20 that showed up in my garage this weekend because I volunteered to rebuild the magdyno and to properly wire the bike. Right now the only wiring it has runs from a lantern battery in the tool box to the brake light.

Anyway, for months I've been searching for an insignificant part for my Spitfire but without any success. That part is the plate for the hole in the timing cover intended for the tachometer drive, as shown in the following photograph from much earlier in this thread.
[Linked Image]

The missing plate would be 2" in diameter and with two holes spaced 1-9/16" apart. Whether it's made from Al or steel I could make it myself. But, what is it made from and, assuming it's steel, should it be cadmium or chrome plated?

I suspect the problem is that by this point most such plates would have been trashed and actual tach drives installed in their place. But, I really, really need to know what an original was made from so please check your pre-unit singles and twins parts boxes to see if you have such a plate. Thanks very much in advance.
Posted By: Boomer

Re: 1957 BSA Spitfire Scrambler - 01/20/16 6:24 pm

They are steel and looking at one on one of my engines I would say they were painted a dull silver, maybe the same color as the centermount oil tank?


Bill B...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/20/16 9:35 pm

Originally Posted by Boomer
They are steel and looking at one on one of my engines I would say they were painted a dull silver, maybe the same color as the centermount oil tank?
Bill, this is great information. Thanks very much.

On my way home today I detoured ~20 miles out of my way to pick up a gently used Kendon "Stand-Up Middleweight" lift that should go a long way toward easing the current gridlock in my garage. Its horizontal extent is considerably less than my HF lift, which was essential for my purposes. Also, although it is designed to stand on end and take up very little space when not in use, I don't expect that will happen very often.
Posted By: bsahatch

Re: 1957 BSA Spitfire Scrambler - 01/21/16 1:28 am

My 54' Golden Flash has an alloy cover plate but who knows the originality of it; I've had the bike for many years, in storage, waiting to be restored while collecting many of the missing parts.

[Linked Image]
Posted By: Gordo in Comox

Re: 1957 BSA Spitfire Scrambler - 01/21/16 1:20 pm

So I see we have steel and alloy. I made an alloy cover for one of my GS covers but have no solid info of what the original covers were made from. This weekend I will be getting together with some of the BSA old timers and will find out what I can about the originals.

Gordo

[Linked Image]
Posted By: mr.moto

Re: 1957 BSA Spitfire Scrambler - 01/21/16 1:32 pm

Hi. I still have one of these new old stock. Sorry but I dont want to part with it, however I can measure it for you.
Originally it was cadmium plated but they do look good in chrome. The outer dia. is 2.004", the thickness is 0.675" in steel of course. The 2 holes are about 7/32"
Hope that is enough info?. Pat A.
Oh, and the original bolts had hexagon heads drilled for wiring.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/21/16 1:41 pm

Guys, I can't that everyone who responded enough. But, one guy (who I won't name unless he says it's OK) I'd like to thank even more than enough. He wrote to say he has a NOS one complete with screws and washer that he will be sending me. This Forum is great.
Posted By: Gordo in Comox

Re: 1957 BSA Spitfire Scrambler - 01/21/16 1:51 pm

MM: Is it your birthday?

Gordo
Posted By: BritTwit

Re: 1957 BSA Spitfire Scrambler - 01/22/16 12:26 am

PS – same as G.S. Catalina and Super Flash/Road Rocket
67-0714 plate
67-0715 gasket
67-0716 bolt (same as 27-4258 gear box inspection cover screw but has hole for safety wire)
65-9163 sealing plate bolt safety wire
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/14/16 8:52 pm

Work on the Spitfire was interrupted because I was overcome with the urge to fly to Australia to ride a 350 c.c. Gold Star for a day. Thanks very much to the Forum member who set this up and for his hospitality as well as that of his neighbor, and to the several other Forum members as well who I met while I was on the other side of the known universe.

Despite that trip, some progress still was made recently. Thanks to the generosity of one of the Forum members who lives half a world closer a new old stock cover plate with the two screws drilled for lockwire arrived. This is shown below temporarily attached to a Gold Star timing cover for making the photograph.

[Linked Image]

Acquiring this plate may not seem like much, but it definitely helps move things forward. It's remarkable how much time has to be spent on little things, and in the end they are just as critical to the overall success of a restoration like this one as are the big things. Again, thanks to the benefactor who also is a Forum member.
Posted By: Boomer

Re: 1957 BSA Spitfire Scrambler - 12/09/16 3:08 pm

This thread should be sticky noted to the top of these postings.


Bill B...
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/10/16 12:31 pm

Originally Posted by Boomer
This thread should be sticky noted to the top of these postings.
Admit it, you wrote that to shame me into getting back to work on the Spitfire, didn't you? It's amazing how fast a year goes by... I hadn't realized until today that the Spitfire thread has the 2nd highest number of views in the Projects forum, less than 20% behind TR6Ray's Triumph restoration that has been here twice as many years. Given the interest, I better get busy again.

In my defense, my acquisitions of BB and Catalina Gold Stars diverted much of my attention this past year (as if I needed the aggravation, earlier this week UPS lost the Catalina's front brake being returned from Vintage Brake...). Anyway, when the time comes I'm going to count the thread on rebuilding a 6-spring clutch towards the Spitfire, as well as rebuilding its K2F magneto even though I'll post that as another Appendix to the magneto thread.

I plan to waste as much of the Christmas break as possible riding motorcycles rather than working on them, but I should be back to work on the Spitfire's gearbox by the end of December.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/29/17 12:28 am

I've been doing a bit to get the Spitfire restoration moving again. There are five bearings in the gearbox and I have NOS bearings to use. However, the following should be of interest to others who aren't so lucky and who need to source modern replacements that have the correct specifications.

There isn't much useful information on this topic on line, and a good fraction of what I could find is incomplete or wrong, so I spent a fair amount of time to track down contemporary catalogs of Hoffmann, Norma-Hoffmann, R&M, Skefko (SKF) and Torrington, as well as I've used relevant information from catalogs issued within the past 20 years by FAG, INA, MRC, NTN, SKF and Torrington-Fafnir. I'll soon post a more extensive version of this that also includes Gold Star engine and clutch bearings as well as additional technical information.

The bearings used by BSA are listed in Service Sheet 703 and the part numbers are in Spares catalogs:

_________________________BSA___Hoffmann__ R&M______Skefco____ Fischer__ Torrington
Gearbox:

Sleeve gear mainshaft _______ 24-4065 ___ 135 _____ LJ35 ______ 6207 ______ 6207 _____ -----
Outer mainshaft ___________ 24-4217 ___ LS8V2 ___ LJ3/4 ______ RLS6______ LS8 _______ -----
Inner housing layshaft ______ 42-3074 ____ --- _______ --- _______ --- ________ --- ____ M-11121-OH
Outer layshaft _____________ 42-3075 ____ --- _______ --- _______ --- _______ --- ____ B-1212-OH
RRT2/SCT2 sleeve gear _____ 42-3135_____ ---_______ --- _______ --- ________ --- ____ B-1314-OH

R&M formerly Ransome & Marles
R&M, Hoffmann, and Pollard merged to form RHP, later purchased by NSK. The RHP brand is still used by NSK.
SKF formerly Skefko (the name of the UK's SKF subsidiary)
FAG formerly Fischer (stamped F.B.C. on the original bearings)

While bearings with the same or similar brands as were originally used are manufactured today the trademarks no longer can be relied on to indicate the country of manufacture.

Needle Bearings

Although full complement needle bearings were originally used it is common for aftermarket motorcycle parts suppliers to stock caged bearings having roughly half the number of rollers. According to engineering formulas in a c1970 Torrington catalog, under identical conditions such caged needle bearings will have only 21% the lifetime of full complement bearings of the same size and quality.

A Torrington B-1112-OH can be used on the layshaft instead of an M-11121-OH, but the former is an open-ended bearing so it would need a plug on the outside.

The Oil Hole (OH) is a modification to the basic Torrington needle bearing and is marked on the packaging but not on the bearing itself.

Ball and Roller Bearings

Since there was no industry standard for labeling at the time it is essential that the manufacturer as well as the part number be specified when looking for a replacement. For example, Hoffmann used RMS11 for a roller bearing (drive side Gold Star engine) but SKF used that same code for a ball bearing.

There are a large number of codes to designate various features of modern ball bearings, but the following suffixes are relevant and fairly common:

Radial Internal Clearance (also called Diametrical Clearance)

This is the most important specification since the wrong clearance will mean the difference between excess noise (too loose) and rapid bearing wear (too tight). The current system uses ABEC grades of fit (sometimes listed as AFMBA) that somewhat confusingly are 1, 2, 0, 3, 4, and 5 in order of increasing looseness. Verbal descriptions of some of these fits in a modern Torrington-Fafnir catalog are 'Snug' (2), 'Medium' (0), 'Loose' (3) and 'Extra Loose' (4), with 0 also commonly termed 'Normal'.

As a modern SKF catalog says, "As a general rule, ball bearings should have an operating clearance that is virtually zero." Since installation involves a press fit of ~0.002" into Al this causes the diameter of the outer track to decrease by approximately 50% of the interference fit (e.g. by ~0.001" if the housing were exactly 0.002" smaller than the bearing). This has to be compensated for by using a bearing having the correct internal clearance prior to installation. If you feel any resistance when turning the inner race after installation the initial clearance was too small and the bearing will fail prematurely in service.

On the original ball and roller bearings used by BSA the diametrical clearance was denoted by circles lightly polished or stamped on the face of either the inner or outer race. According to a 1968 Skefko (SKF) catalog there is a one-to-one correspondence between the "circle" clearance grades and the "C" grades now used on modern bearings:

C1 ___ ---- ___________ Less than C2
C2 __ one circle _____ Less than normal clearance (such a bearing almost certainly would be too tight once installed)
CN __ two circles ___ Normal clearance (typically not indicated on a modern bearing; All five original gearbox sleeve gear ball bearings I examined had two circles)
C3 __ three circles ___ Greater clearance than normal (three circles; this almost certainly would be too loose, especially if the bore is worn)
C4 __ four circles ___ Greater than C3 (almost certainly would be too loose)
C5 __ ----- _________ Greater than C4

As can be seen from the next photograph the circles are lightly polished or stamped on the stamped face of the outer ring of Hoffmann bearings and on the inner ring of R&M. These circles are very light and can be difficult to see unless inspected closely with a magnifying glass.

[Linked Image]
The two images in the above composite are at the same magnification showing the full width of the Hoffmann outer race (top) and R&M inner race (bottom) of Gold Star timing side roller bearings.

Tolerance

This is not the same as clearance. Tolerance classes refer to allowed variations from nominal of the diameter, width, eccentricity, etc. Three systems for denoting tolerance of ball bearings have been commonly used in recent decades (another, RBEC, for roller bearings):

DIN _____ ANSI ___ ISO
P0 ______ ABEC 1 ___ 0 _____ Normal tolerance (typically not indicated on the bearing)
P6 ______ ABEC 3 ___ 6 _____ Higher tolerance than P0
P5 ______ ABEC 5 ___ 5 _____ Higher tolerance than P6
P4 ______ ABEC 7 ___ 4 _____ Higher tolerance than P5

Evidence I've collected suggests the gearbox bearings were of no higher tolerance than ABEC 1.

Seal Type (none of the original Gold Star bearings had seals):

Codes for seals are not universally used by all manufacturers, but the following illustrate some of the common types available.

RS Rubber seal on one side
2RS Rubber seals on both sides
Z Metal seal on one side
ZZ Metal seals on both sides

Cage Type

These codes are not universally used by all manufacturers, but illustrate some of the common types available.

F Steel cage
M Brass cage ball guided (all five original gearbox bearings I examined have ball-guided brass cages)
MB Brass cage, inner ring centered
MA Brass cage, outer ring centered

The specifications and descriptions below are from contemporary R&M, Skefko (SKF) and Torrington catalogs. These specifications are for the bearings that were originally supplied to BSA so will be of use to anyone searching for modern replacement bearings that are equal or better:

ID _______ OD ___ width _____________ Static Capacity ___ Dynamic Capacity ____ Max. rpm
Gearbox Sleeve Gear Ball (single row rigid ball journals, ball-guided brass cage, light type)
35 mm __ 72 mm __ 17 mm _______________ 3050 lbs. _________ 4400 lbs. ___________ 10,000

Gearbox Outer Mainshaft Ball (single row rigid ball journals, ball-guided brass cage, light type)
3/4" ____ 1-7/8" ___ 9/16" ________________ 1430 lbs. _________ 2200 lbs. ___________ 16,000

Inner Housing Layshaft Needle (full complement, closed cup with oil hole)
7/8" _____1-1/16" __ 0.85" (0.66" depth) ______ 2530 lbs. ________ 3530 lbs. ____________ 4200

Outer Housing Layshaft Needle (full complement, open end with oil hole)
3/4" ______ 1" _____ 0.75" _________________ 3180 lbs. ________ 3790 lbs. ____________ 5500

RRT2/SCT2 Sleeve Gear Needle (full complement, open end with oil hole)
1-1/16" _ 1-3/16" __ 0.875" __________________ 3880 lbs. _______ 4960 lbs. ____________ 5200

Note: A rear wheel makes ~750 turns/mile. With a 46T rear sprocket and 16T gearbox sprocket the sleeve gear ball bearing will turn 46/16 x 750 = ~2150 turns/mile. So, even with this relatively low gearing, at 120 mph (2 miles/min.) the bearing will be turning at ~4300 rpm, which is well below its rated maximum.
Posted By: Dana_twin

Re: 1957 BSA Spitfire Scrambler - 06/05/17 6:58 am

Great info.... thanks! The bearing nomenclature is a minefield and terms seem to differ greatly between manufacturers.. Doesn't help that companies like Locate Bearings show only a box (not the bearing) and calling them for details/info is useless as well. Lots of times it's just rolling the dice and hoping what they send is what's needed. Any idea what the RHP designation 'V3' refers to? I was told that 'c3' and 'v3' specs are interchangeable but you never know with this. Online sellers are claiming equivalent to the old specs and charging tons without knowing the product is wrong /inferior. Not all but some.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/06/17 6:36 pm

Originally Posted by Dana_twin
Any idea what the RHP designation 'V3' refers to? I was told that 'c3' and 'v3' specs are interchangeable but you never know with this.
V and C are completely different specs. C gives the amount of radial clearance deliberately built into a ball bearing to ensure that once installed in a housing and at operating temperature the working clearance will be as close as possible to zero. Because press fits of bearings of the sizes we care about might be ~0.002", the 'C' clearances are of order ~0.001". That is, sitting on the table the inner race could be moved radially back and forth by this amount with respect to the outer race

A bearing in a given tolerance class, e.g. P6, has different allowable manufacturing tolerances for each of the relevant dimensions other than the difference in diameters of the race tracks themselves (outside diameter, bore diameter, inner ring width, etc). For these dimensions, the V tolerances could be as large as ~10 micrometers (0.0004") for our bearings. Because most buyers probably don't want to spend the time to individually specify the acceptable V tolerances on each dimension they're lumped together in the P tolerance classes. If you pay for a higher P class the individual V tolerances are better than you would get in a lower P class.

What this means is you could order a bearing that has a very small radial clearance (C1) when it is on the table but with sloppy tolerances on the other dimensions (V6). Or vice versa. But, even if the clearance was fine on the table, if the dimensional tolerance of the bearing's OD was in the direction of being large, the installed clearance could end up less than you wanted.

Stated differently, the clearance (C) of a bearing is a precisely manufactured amount of radial difference to allow for the installed, working environment, while tolerance (V) is the amount of allowable manufacturing deviation of various dimensions from the nominal specification. Because C is a clearance it is always a positive amount. Because V is a tolerance (i.e. +/-) a given dimension could be greater or less than the nominal value it is supposed to have.
Posted By: BikeVice

Re: 1957 BSA Spitfire Scrambler - 06/06/17 11:29 pm

Originally Posted by Dana_twin
Any idea what the RHP designation 'V3' refers to?


The V rating is a vibration rating, the P ratings are precision ratings and as explained above the C ratings are clearance ratings. There's really no relation between the 3. I believe the vibration is measured as noise and a bearing with a high V number might have rounder balls and/or a better surface finish than a bearing with a lower V number.

Eric
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/07/17 12:48 am

Originally Posted by BikeVice
The V rating is a vibration rating,
I have 13 bearing catalogs (I just counted them). When I went though them all a few months ago I didn't find any that deviated from the radial clearance definition I quoted in an earlier post for C0, C1, etc. However, V doesn't seem to be as universal. Although most catalogs are pretty bad at making it easy to find definitions an INA catalog has a 2-page list of "symbols and units of measurements. It defines V1, V2 as "Load factors for periodically varying bearing load."

The important thing is, 'C' is the very-important radial clearance that will determine if your engine will have a knock, the bearing will wear out too fast, or all will be well. Any symbol other than C is not the radial clearance no matter what a retailer might say.
Posted By: BikeVice

Re: 1957 BSA Spitfire Scrambler - 06/07/17 2:16 am

Originally Posted by Magnetoman
Originally Posted by BikeVice
The V rating is a vibration rating,
I have 13 bearing catalogs (I just counted them). When I went though them all a few months ago I didn't find any that deviated from the radial clearance definition I quoted in an earlier post for C0, C1, etc. However, V doesn't seem to be as universal. Although most catalogs are pretty bad at making it easy to find definitions an INA catalog has a 2-page list of "symbols and units of measurements. It defines V1, V2 as "Load factors for periodically varying bearing load."


Well I don't have 13 bearing catalogs, nor would I want them, but a 5 minute Google search confirmed that the V rating is a common vibration classification. Testing is done on a BVT-1, whatever that is, and the classes are V, V1-V4, with V4 being the smoothest.

One of many confirmations:

http://www.microbearing.com/list.asp?catid=392&typeid=0

Originally Posted by Magnetoman
The important thing is, 'C' is the very-important radial clearance that will determine if your engine will have a knock, the bearing will wear out too fast, or all will be well. Any symbol other than C is not the radial clearance no matter what a retailer might say.


Agreed

Eric
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 06/07/17 6:02 am

I have always taken the V as vibration class, but as the old bearings in our engines are pre ISO bearing stds the markings have to be read based on the manufacturer and what they were doing at the time. So as these are mainly RHP we need an RHP catalogue from the 50/60's and its section on markings.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 06/07/17 5:22 pm

Originally Posted by kommando
as these are mainly RHP we need an RHP catalogue from the 50/60's and its section on markings.
As I wrote in an earlier post in this thread "I spent a fair amount of time to track down contemporary catalogs of Hoffmann, Norma-Hoffmann, R&M, Skefko (SKF) and Torrington,..." Fischer (FAG) is now on that list, so I have catalogs from the 50/60s for all bearings used by BSA at the time, and the information I was able to extract from those is in that earlier post.

I won't take the time to go through them again at this point to check, but I don't remember vibration being a specification discussed in any of them so apparently it wasn't a factor they were too concerned with 50 years ago. At least, not for general bearings. Formulas in the catalogs for calculating expected lifetimes do not contain terms to incorporate the vibration due to tiny deviations from perfection.

More generally, none of those catalogs contains enough information to identify all the markings on the bearings I have. Some of the markings are still a mystery to me. At least one catalog instructs the reader to contact the company for additional technical information not contained in the catalog.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 06/07/17 7:04 pm

At Glacier Bearings we also fed only what the application engineers wanted to customer to know and told them to contact the application engineers for anything more. The thinking was if you told them too much then they either would no longer need a bearing maker, or make a complete balls up plus the danger of telling all your secrets to the competition. As it was with the little information they were given they still, if left to their own devices, balls it up, Ford wanted a corrosion coating for storage which we gave them in the form of a zinc flash which was sacrificial and gone in the first few hours of running, a few years later they started to fail the bearings after engine tests saying the zinc layer had gone DOH!!! They were told the reason and it was accepted, and then 5 years later the cycle would start all over again with more failures.

As V3 is a marking I see a lot on BSA and Triumph mains is a high V rating and added to the cost, the bearing supplied must have been specified to have that rating, we will never know why now but its seen too often to be a coincidence.
Posted By: Nick H

Re: 1957 BSA Spitfire Scrambler - 11/26/17 12:30 am

Here is what looks like a very interesting thread that has been ruined by Photobucket. It would be great if people could go back and edit their posts and fix their pictures. Add ~original after the last .jpeg or .png and the [/img]

example: [img]http:\\photo$&£€#!?#.jpeg~original[/img]

Tedious, but I fixed a few of mine.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/26/17 3:21 am

Originally Posted by Nick H
It would be great if people could go back and edit their posts and fix their pictures...Tedious, but I fixed a few of mine.
There are two problems with your suggestion. I just tried it and it didn't work, and even if it did it would have been too tedious and time consuming to go through all my posts to do this even if there were some assurance Photobucket wouldn't block the fix in a few days or weeks. I need a reliable, permanent fix before I spend time to get images to work again.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 11/26/17 10:09 am

This would be best achieved using a script to do it automatically, I will raise it with Morgan.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/18/18 10:05 pm

I had thought that I stopped work on the Spitfire when my Ariel arrived 18 months ago, which was a good excuse for not having worked on it since then, but looking back through this thread I see that I've done essentially nothing since November of 2015. So, while waiting for an Ariel valve blank to arrive, and since nothing can possibly go wrong working on several projects in parallel, I decided to ramp my effort on the Spitfire back up. Besides, no longer facing a hard deadline to have the Ariel fully functional means there's no longer any urgency with it.

When I last worked on the Spitfire I needed to finish refurbishing the gearbox and reassemble it. The open issue was how to make the case look as good as new, but not overpolished and better than new. I have HF to etch the surface but, since then, discovered that a Gunk+diesel degreasing mixture can do a remarkably good job. So, today the three pieces that make up the gearbox housing went into that solution to soak for a week.

OK, OK, this is a pretty passive development to claim as "work," but haste makes waste.


Attached picture SCT2_degreaser.jpg
Posted By: AML

Re: 1957 BSA Spitfire Scrambler - 11/19/18 2:32 pm

I've been looking forward to the revival of this thread!
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/19/18 6:09 pm

Originally Posted by AML
I've been looking forward to the revival of this thread!
Because of other obligations I won't be able to do any more work on the Spitfire for a week, but this is an actual revival, not a post about hoped-for work that might or might not happen. As a result of rebuilding the Ariel, several relevant developments since my last real work on the Spitfire are that I now have a Sunnen hone and Magnaflux kit, as well as the ability to build up metal with Stellite, copper, and hard chrome.

BSA Service Sheet 702 lists the diameters of the bushes used in the various models and I have Sunnen mandrels for all of them (and many more, covering 0.106" to 4.2"), from the 0.218" speedometer spindle to the 2.756" cylinder bore. This should allow me to assemble the bike with a bit better precision than when it left the factory. Since finishing the gearbox is at the top of the list, the first component to benefit from the Sunnen will be the bush that fills half the sleeve gear (with a bearing in the other half).
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/26/18 3:42 pm

The real reason for soaking the gearbox covers for a full week is I "had" to make a three-day trip to France (nb. I'm sure there's a compound word in German, but I can't think of an appropriate English word for agreeing to do something that you enjoy doing). It was a bit chilly, but perfect for walking around the picturesque city of Besançon, and the ever-changing weather forecast managed to keep moving its 100% chance of rain predictions away from the times I would be outside.

Anyway, with France dealt with, I'm now back to dealing with the Spitfire. I've now learned from Kibblewhite that the Ariel valve blank I need is still backordered, reducing temptation to work on the Ariel even though I could usefully machine and install a new guide and do the final honing to size after the valve arrives.

Since no such guide seems to exist on the web I've started photographing the various components in order to produce a comprehensive "manual" over the next several posts for rebuilding pre-unit BSA gearboxes at the level of detail of my six-spring clutch thread


Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/27/18 2:29 am

Before starting to document the assembly of my gearbox I skimmed through this thread to see what I had previously posted and was impressed to discover how much work I've already done. The nice thing about spreading a rebuild out over so many years is not realizing how much time has been squandered. Anyway, to (re)start the gearbox rebuild, this post contains some information that I don't think is commonly known.

There are four spacers critical to the smooth operation of T-type gearboxes that are not clearly illustrated in the parts manual so the first two images show their positions and thicknesses. It's important to note that #73 and #74 are not used in Standard-type gearboxes It might seem with 8 gears, some of which could be installed in either of two orientations, that getting the correct gears in the correct locations would be nearly impossible. However, it's actually not that difficult, and the second photograph should help make it even easier.

Because there is a slight taper, rather than a sharp edge, where the inside end of the layshaft meets the splines, and depending on production tolerances, that taper might extend slightly beyond the face of the gear (e.g. at the left side of the gear that's at the top of the third photograph, which has the spacer in question positioned against the face of the gear). A subtle point is both sides of the IDs of OEM spacers are chamfered allowing them to be installed in either orientation without hanging up on that taper. However, if an aftermarket spacer doesn't have the chamfer, or has it only on one side and is incorrectly oriented, the spacer might not sit flush with the gear. If this is the case the hardened spacer will have to be relieved by grinding before it is installed.

Unfortunately, a huge pitfall awaits someone assembling a gearbox from mixed parts because some of the "equivalent" gears in bush-type (e.g. STD2) and in T-type (e.g. ASCT, SCT2, etc.) have different widths. Referring to the standard BSA gearbox chart, note that gear 'B' on the STD2 and SCT2 both have 18T (although a closer look at the chart reveals they have different part numbers). Unless careful, even when holding the gears side-by-side you might not notice there's a difference, but the third photograph shows that gear B on the bush-type layshaft (at the bottom, with a scroll at the end of the shaft is narrower than that on the T-type layshaft (at the top, with a smooth end on the shaft).

Although I had never before taken the time to measure the width of gears, now I have, albeit only for one of each type, i.e. STD2 and SCT2. Although for some gears it's clear what is meant by the width, the fourth and fifth images show how I determined it in unclear cases. Although I measured each of the widths to 0.001", below I list the values rounded to 0.01" because with only two examples I don't want to imply precision that might not be present due to production tolerances.

__________ width
Gear_STD2 ___ SCT2
A ___ 0.68" ____ 0.70"
B ___ 0.70" ____ 0.78"
C ___ 0.88" ____ 0.85"
D ___ 0.59" ____ 0.60"
E ___ 0.68" ____ 0.86"
F ___ 0.94" ____ 0.93"
G ___ 0.86" ____ 0.86"
H ___ 0.54" ____ 0.54"

As can be seen from the above values, both B and E are different between the two types of gearboxes,(*) although the 0.03" discrepancy of C must be within the production tolerance as can be deduced from comparing part numbers. As a result, to assemble a gearbox from mixed parts requires a set of calipers along with the usual sockets and spanners.

(*)Note: I came across an unattributed reference that gives different figures than above, which means they used different points across the teeth for measurement, and also says that Gear A is wider for the T-type gearbox as well (although it doesn't mention E as being different). Although this might seem to be confirmed by the different part numbers for A for the two gearboxes I measured, A is a special gear for the SCT2 since it contains a needle bearing so it would have a different part number no matter what. However, it's even more complicated for earlier gear sets. For example, the RR and RRT used the same 25T Gear A as each other (but different than in later gear sets), as do the DAY and DAYT for their 26T gear (again, different than in later gear sets). In all the chart has five different part numbers each listed for 25T and for 26T Gear A. Clearly, what is needed is a table of widths, all measured in the same way, for all the gears BSA used over the years. Unfortunately, this is greatly complicated by the fact in most cases gearboxes might have been rebuilt at some time in the past 60 years using one or more incorrect gears, coupled with the fact there are no part numbers on the gears.


Attached picture Gearbox_assembly_001.jpg
Attached picture Gearbox_assembly_002.jpg
Attached picture Gearbox_assembly_003.jpg
Attached picture Gearbox_assembly_004.jpg
Attached picture Gearbox_assembly_005.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/28/18 4:55 am

Originally Posted by Magnetoman
I skimmed through this thread to see what I had previously posted and was impressed to discover how much work I've already done.
A friend called today and pointed out I also had contributed material to a gearbox 'sticky' thread on the Gold Star forum, which I'd also forgotten about. Sigh...

He also suggested that instead of hiding my gearbox rebuild in this thread about an obscure model, I should make it stand-alone so it would be easier for BSA owners to find it later. That's an excellent suggestion, that I agreed to, but upon reflection and review of what I've already written, I'm going to implement a modified version of his suggestion. I'll continue with the rebuild here, while off-line I'll start organizing a stand-alone rebuild thread that will include this material, and more, although organized in a straightforward way. Also, since I'm now at the point of putting the Spitfire's gearbox back together, I'll need to document taking another one apart to have a complete thread anyway.

When I took the gearbox components out of the bucket of diesel+Gunk I noticed a couple of cracks in the lid. Since they could have let rain water in I bought a new bucket and decanted the old one into it. The first photograph shows the dregs, which must be congealed grease. Interestingly, even though I haven't cleaned very many things in that bucket the mixture has managed to remove ~25 cu.in. residue, which speaks well of the cleaning power of this solution.

As I took them out of the bucket I spent maybe two minutes each on the three gearbox castings with #0 Medium Fine stainless steel wool, followed by washing with soapy water and paper towels. Although a difference in reflectivity of only a few percent makes a big difference visually, it's difficult for a camera to capture. The best I could do was to position the cleaned SCT2 casting with an uncleaned one to directly reflect sunlight. As the blown out highlights in the second photograph show, that nearly obscure the 'T2', the casting I cleaned with very little effort is significantly more reflective.

The next step in the rebuild will be to replace the sleeve gear bearing and seal. These are held in place with an internal retaining ring that doesn't have holes for using "standard" retaining ring pliers, as shown in the next photograph. While it's relatively easy to worry the ring out of the groove using a pick or small screwdriver, getting it back in again can be quite a hassle. The next two photographs shows a "tool" I made that makes this job much easier. I get one end of the ring started in the groove then while pushing down I"walk" the tool around it to push it into position, sometimes helped by pushing inwards on the ring from the side with a thin screwdriver.


Attached picture Gearbox_assembly_006.jpg
Attached picture Gearbox_assembly_007.jpg
Attached picture Gearbox_assembly_008.jpg
Attached picture Gearbox_assembly_009.jpg
Attached picture Gearbox_assembly_010.jpg
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 11/28/18 10:03 am

Interesting degreasing solution, what's the ratio of diesel to gunk and what type of gunk are you using?
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/28/18 3:46 pm

Originally Posted by gunner
what's the ratio of diesel to gunk and what type of gunk are you using?
I thought I had described it earlier in this thread, but instead it is here. Since I wrote that post I learned diesel is available in at least two mixes with #2 specified for modern cars (which is what I used) and #1 having a higher ratio of kerosene in it (which is what I would have used if I had known about it and could find it). Unfortunately, a quick search didn't show any sources of #1 where I live, although it may be so common at truck stops that no one bothers to explicitly list it. However, I wouldn't dump out my current mix even if I did find #1 now. Also, as a friend in New York recently discovered, diesel fuel begins to congeal at ~32 oF and gels at ~15 oF, so those of you who live in colder climates will have to keep your 5-gal. bucket of degreaser in the kitchen if you want to use it over the winter months.

Originally Posted by gunner
I don't think the wife would be too impressed with a bucket of degreaser in the kitchen!
I haven't tried, but I bet it would work better than any standard kitchen detergent on pots and pans.
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 11/28/18 4:09 pm

Great, thanks for that MM I will try my own experiment with Diesel/Kerosene and use the one of the Gunk formulations available in the UK.

You seem to have had very good results which is something I want to try and replicate.

Luckily my garage is attached to the house so it never gets below freezing & I don't think the wife would be too impressed with a bucket of degreaser in the kitchen!
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 11/28/18 8:36 pm

Hi MM and All,
In photo four in above in post 737573 showing the "tool" and circlip

This photo shows a very common error !!!!!!!!!
The circlip is not fully seated opposite its open ends
It should be concentric with the seal step and casing bore
The inner face of the seal has rings of the sealing material standing proud of the base material
These have to be compressed in order to get the circlip to seat fully
It can be a real struggle to get the circlip fully seated on some (most) gearboxes!!
Clamping the assembly usually grips the circlip and does not allow it to expand
Working around the circlip circumference with a blunt ended brass punch and small hammer helps then you may
also work on the circlip ends to "encourage" it to seat fully

Almost all the BSA gearboxes I have worked on have arrived with the above problem and oil leaks to go with it
On one particularly stubborn box I had to resort to sanding the inner face of the seal in order to seat the circlip

John






Posted By: Jay Gilling

Re: 1957 BSA Spitfire Scrambler - 11/28/18 10:30 pm

Originally Posted by Magnetoman
Originally Posted by gunner
what's the ratio of diesel to gunk and what type of gunk are you using?
I thought I had described it earlier in this thread, but instead it is here. Since I wrote that post I learned diesel is available in at least two mixes with #2 specified for modern cars (which is what I used) and #1 having a higher ratio of kerosene in it (which is what I would have used if I had known about it and could find it). Unfortunately, a quick search didn't show any sources of #1 where I live, although it may be so common at truck stops that no one bothers to explicitly list it. However, I wouldn't dump out my current mix even if I did find #1 now. Also, as a friend in New York recently discovered, diesel fuel begins to congeal at ~32 oF and gels at ~15 oF, so those of you who live in colder climates will have to keep your 5-gal. bucket of degreaser in the kitchen if you want to use it over the winter months.

Originally Posted by gunner
I don't think the wife would be too impressed with a bucket of degreaser in the kitchen!
I haven't tried, but I bet it would work better than any standard kitchen detergent on pots and pans.



Home heating oil has the kerosene mix which you can just buy separately as well. As far as diesel gelling in cold climates, You can also just buy a bottle of diesel antigel and mix it in. I keep some diesel with 6 oz of antigel outside in a shed that reaches -30F -40f just as a back up for a generator and there are no issues.

Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/28/18 10:48 pm

Originally Posted by chaterlea25
This photo shows a very common error !!!!!!!!!
That's a good point and in light of your comment I should have noted the issue in my original post. I took an empty housing from the shelf to use to make that shot of the tool, and the fact the tool isn't sitting flat in the last photograph of that post certainly shows the snap ring in that housing isn't properly seated.
Originally Posted by chaterlea25
It can be a real struggle to get the circlip fully seated on some (most) gearboxes!!
+1 on that observation. Even on "easy" gearboxes it's a struggle, which is why I made that tool.

Showing one of the landmines that awaits a rebuilder, the only gear in my SCT2 that has a part number on it is H, shown in the first photograph. However, 42-3082 does not appear anywhere on BSA's gearing chart. Unless someone had a BSA 'Master Priced List' from later than 1959 they wouldn't know that this number was superceded by 42-3210, which is on the chart as the correct gear for an SCT2.

Back to assembling the gearbox. If there is excessive wear of any of the bushes (or sleeve gear needle bearing, in the case of the RRT2/SCT2), press the old one out and the new one in. You may have to ream or hone the new bush after installation. These finer points of assembly will be discussed later in an Appendix.

During inspection of the components note that the layshaft is hollow and has a number of holes for feeding oil to the gears as shown in the second photograph. Even if you didn't press gear B off and back on again, make sure that its oil hole is lined up with the corresponding oil hole in the shaft. Also, as better seen in the inset, there is a steel "O-ring" under the dogs that serves to locate the position of the gear when pressed onto the shaft. Make sure it is present and that the position of the gear on the shaft with respect to it is as shown in the photograph.

As shown in the third photograph, if you need to replace the sleeve bearing remove the circlip with a screwdriver (or two), then remove the oil seal. Clean residual oil off as best you can to reduce the smell and heat in an oven to ~225 oF. The bearing may fall out at that point when rapped against a wood table, but have a suitable drift ready in case it needs a few taps. The fourth photograph shows a 1-5/16" socket with extension that would work as a drift.

The final photograph shows that the 'tophat' shape of the bush in a bush-type gearbox housing serves as a stop to locate the in-out position of the bush, but be sure to install it with the oil hole facing the drilling in the housing. If you are replacing the bush it's convenient to have everything ready to press it into place while the housing is still hot. This photograph also shows that the needle bearing in a T-type gearbox is installed with its outer edge flush with the countersink in the housing. I note this because Torrington recommends having it protrude by a certain amount. As is the case with a bush, make sure the oil hole in the needle bearing is aligned with the hole in the housing.

Originally Posted by Jay Gilling
Home heating oil has the kerosene mix which you can just buy separately as well.
You can also just buy a bottle of diesel antigel ... shed that reaches -30F -40f
Thanks very much for that information which will be quite helpful for those in colder climates. Heating oil and -40oF temperatures aren't experienced where I live, but I wonder how much the cleaning effectiveness might be reduced even if the diesel doesn't gel. I'm sure my friend will head straight to the diesel supply store to buy some of that magic antigel, and then report back if it still cleans in a New York minute... er, I mean winter.


Attached picture Gearbox_assembly_011.jpg
Attached picture Gearbox_assembly_012.jpg
Attached picture Gearbox_assembly_013.jpg
Attached picture Gearbox_assembly_014.jpg
Attached picture Gearbox_assembly_015.jpg
Posted By: Jay Gilling

Re: 1957 BSA Spitfire Scrambler - 11/29/18 2:43 pm

No need to go to a fancy diesel supply store , every Home Depot or Walmart sells it.Power Service in the white bottle or Howe’s Diesel Treat. I would think it might clean even better thinned out a little with the dispersants. That looks like it’s coming together nicely.
Posted By: Servodyne

Re: 1957 BSA Spitfire Scrambler - 11/29/18 4:28 pm

Hello Magnetoman it's good to hear that you have started up your fascinating thread again on the 57 Spitfire. I have been reading it with interest since buying my 57 Spitfire from Paul67 who contributed to the thread way back in 2013/14.
I bought the Spitfire as a project and it had been assembled with upswept pipes and 3/4 seat, but I wanted it to be it as close as possible to the original 57 spec but with a bit of room for individuality. I got it up and running last year and I love it, but regret not having the crank balanced as I would like to enjoy more of it's performance. I've recently bought an early heavy crank, which may have been correct for 1957, so I may prepare that with billet rods and 9:1 pistons and get it balanced in readiness for a swop over in the future.

Jim

https://www.youtube.com/watch?v=IMpF7ZD4GN8&list=LLn6l8XGJ6EyXLrc50lQzNWA&index=2&t
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 11/30/18 4:10 am

Originally Posted by Servodyne
. I got it up and running last year and I love it,
Congratulations on a bike that looks and sounds so great. With those pipes, your neighbors much love you.

It's unlikely there will be a problem with the selector quadrant in the middle cover, but if there is the gearchange bush will have to be pressed out, which is best done after heating to ~250 oF. While it is hot also would be a good time to replace the layshaft bush and main shaft ball bearing (standard gearbox) or needle and ball bearing (T-type), if they are worn. If you install a new bush make sure it has the correct clearance. The end of the selector quadrant spindle that's exposed after removing the gearchange bush is threaded 1/4-26 BSF and should be a slip fit. If so it can be withdrawn by hand, although a spacer may be needed if force is required.

Check the fit of the sleeve gear on the main shaft, paying particular attention to this if you have renewed the two bushes that are in it, with a gap between them. If the gear is too tight on the shaft you risk having it seize. If the sleeve gear is for a standard gearbox there will be three oil holes (at 12:00, 4:00 and 8:00 in the photograph) that need to align with the holes in the bush that's nearest the camera. A second bush has no oil holes. If it is an RRT2 or SCT2 there only will be one hole in the face of the gear (shown at 12:00) that has to align with the hole in the needle bearing. Like the other type of sleeve gear there is no oil hole in the bush at the other end of the gear.

Thanks to aftermarket parts, the next step may be the most difficult in any rebuild. I've only measured one gearbox housing so I don't know how much variation there is due to BSA's production tolerances, but in my case I found the following dimensions:

Height of bottom of retaining ring groove above top of Hoffmann bearing: 0.054"
Width of retaining ring groove: 0.074"
Thickness of retaining ring: 0.069" (i.e. this gives it room to move upwards in the groove by 0.005" if forced)
Thickness of the old Hoffmann oil seal: 0.059"

From the above you can see that after installing the 0.059"-thick original oil seal the retaining ring just (barely) fit in the groove with 0.000" additional clearance. The problem is the aftermarket oil seals I have are 0.077" thick, i.e. fully 0.018" too thick to have any chance of installing the retaining ring. And, no, there's no way the rubber coating could be compressed by anything close to this much. As an aside, the metal on both seals is 1.0 mm so the problem is an excess thickness of the rubber coating on the aftermarket oil seal.

I don't have a photograph to show it, but I suggest a trial installation of the retaining ring without the seal in place in order to measure the gap between the ends when you know it is fully seated in the groove. This will give you a value to compare against when you repeat it with the seal, so you will know whether or not the retaining ring is properly seated. In my case the gap was ~5 mm.

I pity the poor rebuilder who doesn't have a lathe, but after removing the excess 0.018" thickness of rubber using a combination of the lathe and 100-grit abrasive paper, and using the tool I showed in an earlier post I was able to install the snap ring with a minimum of hassle. Because of the 0-thou. clearance I worked my way around the seal's housing applying light pressure from a screwdriver blade to get the retaining ring fully into its groove, with the result shown in the final photograph.


Attached picture Gearbox_assembly_016.jpg
Attached picture Gearbox_assembly_017.jpg
Attached picture Gearbox_assembly_018.jpg
Attached picture Gearbox_assembly_019.jpg
Attached picture Gearbox_assembly_020.jpg
Posted By: ducati2242

Re: 1957 BSA Spitfire Scrambler - 11/30/18 10:09 am

I thought I must have been doing something wrong when I was trying to fit that seal . I didn't have the gearbox out and was trying to do it in situ . Luckily I do have a lathe and did similar to yourself but couldn't measure it as well . I always had doubts about what I did but seeing your work puts my mind at ease . Thanks for this .
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 11/30/18 9:00 pm

Hi MM and All,
There is probably a "tolerance" in the housing depths or circlip groove location ????
Only on one occasion have I had to resort to thinning the seal down
I believe that some compression of the seal face is required to prevent oil leakage
Measuring an old seal that has been previously fitted (compressed) may lead to unknown unknown's ??
With zero compression of the seal it may rotate in use!!

John
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/01/18 4:50 am

Originally Posted by chaterlea25
With zero compression of the seal it may rotate in use!!
Even with the tool I made I had to push hard to get the retaining ring into the groove so there's no chance it will rotate. Also, in what I prefer to think is belt 'n braces rather than OCD, there's gasket cement between the seal and bearing.

For those who are interested in such things, on the durometer A scale the rubber on the old seal measures 94 and the new seal 80. For comparison, my Ariel's front tire is 65. The high durometer value is why the ~0.020" thickness of the rubber on the back of even a correctly made new seal can be compressed very little by anyone other than Superman.

Speaking of sealing, the next thing to check in a gearbox rebuild is the condition of the sealing surface of the sprocket since it is subjected to an abrasive mixture of dirt and oil. As a result, in addition to the pits in the surface, the sprocket on the left in the first photograph has a groove 0.007" deep worn into it. A rough surface like this will quickly abrade away a new seal so either needs to be reconditioned, or replaced.

The second photograph shows the what is needed for the next step of installing the sleeve gear. I use a chain wrench I made with drive chain at one end and primary chain at the other end. Also, I made a sprag socket so I can use an impact and/or torque wrench on the nut, although the classic tools are a punch and big hammer.

However, this is as far as I got today because my older daughter called with a 55-gallon leaking fish tank emergency. Not counting the ~40 lbs. of rocks in the bottom or the weight of the stand the tank sits on, the water alone weighs 450 lbs. Siphoning, bucket carrying, and fish wrangling used up the rest of the day.



Attached picture Gearbox_assembly_021.jpg
Attached picture Gearbox_assembly_022.jpg
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 12/01/18 11:54 am

Hi MM, I realise you are keen on keeping the bike original as possible but was wondering if you had considered using a sealed bearing in the gearbox instead of an open one? It would be hidden from view and will stop any leaks so worthwhile in my view.

SRM sell a gearbox sprocket nut with a built in seal designed to stop leaks from the mainshaft, see This Link, so maybe worth considering.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/01/18 3:22 pm

Originally Posted by gunner
Hi MM, I realise you are keen on keeping the bike original as possible but was wondering if you had considered using a sealed bearing in the gearbox instead of an open one? ... SRM sell a gearbox sprocket nut with a built in seal ...
Quoting from SRM's web site the nut will help reduce the oil weep from the gearbox mainshaft when the bike is standing on its side stand, However, like other Gold Star frames produced prior to late 1957, the Spitfire doesn't have a side stand lug. My BB and Catalina also only have center stands, don't leak from their gearboxes when parked, and the oil consumption when under way is acceptable as well.

On a more fundamental level, the "problem" with something like the SRM nut is my compulsion to try to keep the bike as original as possible, whether or not any particular item can be seen (if anyone is aware of inconsistencies with this statement in this thread, please spare me the embarrassment of pointing them out). It's not a question of cost since I bypassed a new sealed bearing that was part of a hoard that came to me a few years ago and instead installed a used Hoffmann that also was in that hoard
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 12/01/18 8:27 pm

Hi MM and All,
When an impact wrench or long lever is used with a "proper" tool to tighten the gearbox sprocket nut,
it can cause the inner diameter of the sleeve gear bush to close up at the outer end a thou or two
Enough to cause seizure in use!!!

DAMHIK
John
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/01/18 9:40 pm

Originally Posted by Magnetoman
I made a sprag socket so I can use an impact and/or torque wrench on the nut, although the classic tools are a punch and big hammer.
Originally Posted by chaterlea25
When an impact wrench or long lever is used with a "proper" tool to tighten the gearbox sprocket nut,
it can cause the inner diameter of the sleeve gear bush to close up at the outer end a thou or two
That's an excellent point, well worth noting.

I have one battery and three pneumatic impact drivers with claimed max. torques of 75, 225, 320, and 700 ft-lbs. Since none are adjustable, the only safe way to use any of them is for removing fasteners. Or for installing fasteners that require higher torque than the max. rating of a given impact driver, followed by a torque wench. The battery-powered one I had along on the Cannonball made me nervous for this reason because it is so easy and convenient to use, but it has a max. torque of 225 ft.lbs. that is ~3x higher than any torque specification on any of our motorcycles other than crankpin nuts.

There will be another work stoppage of a few days, not due to industrial action, but due to grandparenting duties.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/02/18 7:53 pm

While mostly on grandparenting duty today I did manage to sneak into the garage to make a few photographs and measurements. The guy who hoarded the hoard of BSA singles parts that I now hoard didn't seem to throw anything away, no matter how worn. As a result I have 14 spare gearboxes, some of which are assembled or partially assembled. However, of the seven cases that were empty or easy to empty, two have cracked housings under the sleeve gear like that shown in the first photograph.

You might think I'm no better than the previous hoarder was since I haven't thrown out these cracked cases. Although you might be right, in my defense, if these were for a machine for which parts were hard to come by these cases could be repaired to be fully functional by TIG welding and machining. However, for present purposes the important thing is to note that the casting around the bearing is pretty thin and my best guess from the nature of the damage is it was caused by someone hammering the bearing out without having heated the case.

If you heat a gearbox casting to ~225 oF to install the sleeve gear bearing the ~0.0053" thermal expansion of the 2.83" ID cavity is enough that a room temperature bearing will fall to the bottom of the recess under its own weight, requiring no help from a drift. However, if you do this to remove a bearing that's already installed the steel bearing also expands. But, because the bearing expands at a slower rate than the AL, the differential expansion is ~0.0023". The fact it requires a few gentle taps on a drift to remove a bearing this way says the interference fit at room temperature must be ~0.002"-0.0025". I'd have to deploy the inside micrometer for a quantitative check, but this value has to be very close.

If you decide not to bother heating the casting before removing the bearing, look at the first photograph and reconsider your bad decision before you regret it.

Looking at all of these cases lined up on the bench I see data points waiting to be gathered. I only had time to make quick measurements, but they seem to show the distance from the face of the housing to the large diameter faced region around the layshaft bush/bearing is 4.5". As the second photograph shows, because of variations in the castings, to achieve this result required removal of different depths of material. I'll be making much more careful measurements of this dimension to confirm this is the case, and to determine how much production variation there is since in the end that determines the spacers required to give the proper layshaft end float. Also, since the only difference between the standard-type and the T-type housing is in the layshaft bush/bearing, and since the bearing requires a larger diameter hole, it is easy to convert from one to the other. Or back again, with a bespoke bush having a thicker wall.

Anyway, as soon as I get back in the garage I predict I'll head down this rabbit hole for a little while.


Attached picture Gearbox_cracked housing.jpg
Attached picture Gearbox_back face.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/03/18 4:25 pm

As can be seen from the 2nd photograph of my previous post, the area around the bush/needle for the layshaft has two circular regions cut into it. Call these InC and OutC. I measured the ODs of one each of these on a standard and on a T-type housing and found the InC 1.268" on both and the OutC 2.001" and 2.025". These dimensions aren't critical since they just need to be larger than the 1.175" OD of shim #73 and the 1.963" OD of the larger of the two possible Gear B, 18T.

Next, using a depth gauge of better precision than needed, supported on the face of the gearboxes by Brown & Sharpe 'Ultra-Precision' parallels of measured heights 1" to better than 0.0005", and at a garage temperature a frigid 62 °F, I measured the depth below the face of the cases of those two circular areas.

The depths of OutC below the face of the gearboxs for the two T-types that I measured were 4.509" and 4.525". For the four standard type the depths were a bit less at 4.455", 4.484", 4.492", and 4.499". However, given the almost-overlapping ranges it seems BSA was aiming for 4.500" for this depth for both types of gearboxes.

As for the InC, although both types of gerboxes have the same ~1-1/4" OD, the depths are different for the two types. The two T-types I measured were 4.577" and 4.580" while the two standard types were ~0.060" less at 4.518" and 4.522" (the other two housings had bushes installed so I didn't measure them). Although I only have two data points for each type, this difference seems significant since the different widths of gear B causes the face of the T-type gear to be ~0.08" closer to the end of its layshaft.

Before I emerge from this latest rabbit hole I'll have to press a "tophat" bush out of one of the cases and measure the thickness of its "brim" since along with shim #73, the depth of InC, and to-be-measured possible differences in the layshafts, it determines the gap to the face of Gear B, i.e. the end float of the layshaft.

Aside from the depth of InC the only other difference between the cases is the 7/8" (nominal) diameter of the hole for the press fit bush and the 1" (nominal) diameter of the hole for the press fit needle bearing. So, subject to someone pointing out something obvious I missed, the only two things that need to be done to convert a standard gearbox housing to a T-type are to skim an additional ~0.06" from InC and ream the hole larger for the necessary press fit of a needle bearing. Both are very easy operations on a milling machine.


Attached picture DepthMicrometer.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/04/18 3:26 pm

To return to an earlier subject for a moment, in looking for gearbox parts to measure I found a middle casting with the same sort of damage as I noted in several main castings. As the first photograph (again) shows, if you need to remove the bearing from any Al casting you first need to heat it to ~225 °F before you then gently tap the bearing out. The same for installation, although it probably will fall into place under its own weight.

As the 2nd photograph shows I used old fashioned analog technology to measure the lengths of one Standard-type and two T-type layshafts. For the Standard-type the faces of the top hat bushes at either end of the layshaft serve the purpose of thrust washers so neither #73 nor #74 from the first figure in an earlier post is used.

As shown, placing the layshafts upright on accurate 1.000" parallels I used a vernier height gauge to make measurements from the outer surface of Gear B (Standard type) and the outer surface of thrust washer #73 (T-type) to the outer surface of Gear H, i.e. without the 0.113"-thick thrust washer #74. The Standard type layshaft was 4.392" long but the T-types (with #73 in place) were 4.561" and 4.575" long.

As the 3rd photograph shows, the surface in the middle casting against which #74 sits is recessed from the face by approximately the thickness of that thrust washer. In two of the three T-type castings the washer sits 0.006" and 0.0015" below the surface and in the third it is 0.0015" above the surface. The bush in the single Standard-type is 0.005" above the surface, i.e. it has the same thickness as #74 within BSA's apparent production tolerances (the bush measures ~0.116" with calipers vs. 0.1125" for #74 with a micrometer). From these measurements I infer that BSA intended for that recess to be 0.1125" below the surface of the middle casting for both types of gearboxes.

Another aspect that will contribute to end float is the thickness of gasket #46 that sits between the two castings. I don't know how thick the original BSA paper gaskets were but I have a few that might be OEM along with a bag of aftermarket composite gaskets. The uncompressed paper ones are 0.010", the blue composites are 0.016" and the red composites are 0.018".

Putting together information from the past few posts, for the T-type:

Distance of the inner machined circle (against which #73 sits) to the face of the casting: 4.577"~4.580"
Length of T-type layshafts with #73 but without #74: 4.561"~4.575"
Thickness of gasket: 0.010"-0.018" (or ~0.002" if only gasket sealer is used)
Clearance for layshaft in middle casting with #74 in place: from +0.006" to -0.0015"

If all the components are at the ends of their tolerance ranges needed to give max. end float, the end float will be:

4.580" - 4.561" + 0.018" + 0.006" = 0.043"

If, instead, the tolerances conspire to give min. end float, the end float will be:

4.577" - 4.575" + 0.002" - 0.0015" = 0.0025"

It should be emphasized that these variations came from just the few components I measured. If I had measured more components almost certainly the range of variations would be larger.

My measurements on the Standard type aren't as precise because I didn't press the top hat bushings out of the cases to accurately measure the thickness of their brims. However, my measurements with calipers on two of them should be accurate to ~0.002". I only measured one Standard-type layshaft and found it to be 4.392" (without #73 or #74 since neither belong on this type of layshaft) so:

Distance of the inner machined circle (against which bush #77 sits): 4.518"~4.522"
Thickness that the rim of bush #77 sits above the surface: 0.071"~0.090"
Length of Standard-type layshaft without either #73 or #74: 4.392"
Thickness of gasket: 0.010"-0.018" (or ~0.002" if only gasket sealer is used)
Clearance for layshaft in middle casting: -0.005"

If all the components are at the end of their tolerance ranges where they give max. end float, the end float will be:

4.522" - 0.071" - 4.392" + 0.018" - 0.005" = 0.072"

If, instead, the tolerances give min. end float, the end float will be:

4.518" - 0.090" - 4.392" - .002" - 0.005" = 0.029"

In both cases it would seem the addition of a a thicker thrust washer would be needed to get to the BSA's specified range of 0.010"-0.020". Which end of the layshaft such a hardened washer should go on would have to be decided after trial assembly and inspection through the cover.

As can be seen from this, given the variations I found in the components I measured, achieving BSA's recommended end float of 0.010"-0.020" either requires considerable luck, or trial fitting and measurement. The gasket used (or not used) is the biggest and easiest variable over which the rebuilder has control. Once the adjustment possible with gaskets is used up, look into using thrust washers of different thicknesses. The Standard-type gearbox also allows adjustment of the end float using bespoke bushes with appropriate brim thicknesses.



Attached picture Gearbox_BrokenMiddleCasting.jpg
Attached picture Layshaft_length.jpg
Attached picture MiddleCover01.jpg
Attached picture MiddleCover02.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/06/18 2:50 am

Since one can't have too many special tools, and since I know a friend is going to need them in the future, I took time today to make drifts for removing and installing the bearing/bush in the main gearbox housing and in the central casting. They're sized to work both on needle bearings as well as bushes.

On the subject of bushes, one of the first things I did was to heat a case and use one of the new drifts to drive the bush out so I could measure the thickness of its brim. It is 0.111", which is essentially the same as the thickness of thrust washer #73 (0.108") of a T-type gearbox. However, this does not mean the inside face of Gear B for both types of gearboxes starts out the same distance from the housing because the recesses in the housings (that I termed 'InC' in an earlier post) have different depths. I'll return to this point in what follows.

Since the depth of 'InC' is a critical difference between the two types of gearboxes I took the time to very carefully measure it again. I laid out three each of both types of gearboxes and, after checking the calibration of my depth micrometer, measured them at several points inside the recess. For the T-type I measured 4.5770", 4.5812" and 4.5816" for an average of <4.5799">. For the Standard type I measured 4.5170", 4.5182" and 4.5183" for an average of <4.5178">. These show that the InC recess is 0.0621" deeper (call it 0.062"+/-0.001") on a T-type gearbox than on a Standard type.

Note on thermal expansion: Although thermal expansion has an effect on the results on a 4½" Al piece made with a steel micrometer, the difference between measurements made at, say, 60 °F and 75 °F only will be ~0.0005". Still, whenever possible, one should avoid depending on the difference between two large numbers in a machining operation so it would be better to 'zero' at the current surface of InC and then move by 0.062" instead of 'zeroing' at the face of the gearbox and moving 4.580".

Remeasuring Gear B, it is 0.080" thicker on the T-type. The recess in its housing is 0.061" deeper, and thrust washer #73 is the same thickness as the brim of the bronze top hat bush in a Standard type, so this leaves ~0.020" unaccounted for. To get to the bottom of this I measured both types of layshafts gear-by-gear.

As the second photograph shows, after using a flat to make the outside faces of Gear B flush with each other, it can be seen that Gears B+D of the T-type (at the top of the photograph) are still thicker than the Standard type. In fact, the pair is now 0.098" thicker than on the Standard, so we seem to be going in the wrong direction. Don't give up, though.

Making the same measurement on B+F the T-type still is thicker by essentially the same amount (0.095"). However, finally, for B+H the difference is 0.058", i.e. the same amount as the "extra" depth cut into the T-type housings.

Since Gear H and spacer #99 are the same for both gearbox types, the difference must be in the layshaft itself. And, it is. As the third photograph shows the distance from the face of Gear B to the splines against which #99 presses on the T-type layshaft is 3.778". On the Standard-type it is 3.718", for a difference of 0.060". This is the amount by which the face of Gear B on the T-type gearbox has to be closer to the main gearbox housing in order for the face of Gear H to be the necessary 0.113" from the recess in the middle casting. The gears start out at different distances from the main case because of the extra ~0.060" depth, increase those differences as gears are added, but both end up with their Gear H at the same distance because the length to the end of the splines on the T-type layshaft is shorter than on the Standard layshaft.

Another nice feature of the measurements on the two layshafts is they quantitatively confirm the extra 0.061"+/-0.001" depth found with a depth micrometer on the T-type housing within the combined overall uncertainty of ~+/-0.002". Measure twice, cut once...

The second difference between these two types of gearboxes is shown in the fourth photograph. At the top is shown a 1.007"-diameter steel cap of thickness 0.082" (I only measured one cap, but two housings) next to the 1"-diameter recess (0.9986" and 1.0042") of depth 0.150" (0.140" and 0.156") into which the cap is pressed. The cap did not come from this particular gearbox, which can be seen to have a closed-end needle bearing in it rather than the open-end bearing which I believe is what was supplied by the factory. Hence, the need for a cap to keep the oil in.

As can be seen, no such recess for a cap is in a Standard type gearbox. However, the holes for both types are reamed 0.875"-dia. for a ~0.002" press fit with the bearing or bush. The photograph shows a reading of 0.8749" although the bore fluctuated by ~0.0005" along the length. In another gearbox the bore averaged 0.8762" which would have resulted in a press fit of only 0.0005"-0.001" with the OD of a Torrington bearing.

To summarize, the four differences I found between the two types of main gearbox housings are that in a T-type: 1) the inner recess for the layshaft into which thrust washer #73 fits is 0.061" deeper than in a Standard type; 2) the outer recess is ~0.035" deeper, 3) a 1"-diameter recess ~0.150" deep is on the outside of the bore for the needle bearing to allow for press-fitting a 0.082"-thick steel cap, and 4) all T-type, not just the RRT2, are drilled and tapped in both locations for the indexing plunger.


Attached picture RemovalInstallationTools.jpg
Attached picture Layshaft_length02.jpg
Attached picture Layshaft_length03.jpg
Attached picture gearbox_outside.jpg
Attached picture BearingBushingBore.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/07/18 5:09 pm

Before putting away the seven gearbox housings neatly lined up on the workbench I used the opportunity to carefully remeasure the depths of the 'OutC',

For the three T-type these depths are 4.5078", 4.5272" and 4.5370" for an average of 4.5240". The variation is in the actual depths so call this 4.524+/-0.015". For three Standard type these were 4.4842", 4.4912" and 4.4964" for an average of 4.4905". Assuming the same production variation, call this 4.490+/-0.015". Thus, the depth of the OutC for the T-type seems to be ~0.035" greater than that of the Standard type, although the variations are at least half of that difference. Since OutC only provides clearance for Gear B the depth isn't critical, and the variation in the above measurements are consistent with this.

A fourth Standard type has no OutC machined into it, as shown at the left of the first composite, but there are signs that something trapped between Gear B and the case rubbed against it at some point in its life even though the ~0.11" brim of a proper top hat bush is thick enough that there would have been no contact with the gear itself. The depth of the untouched portion at the right of this case is 4.465" and that of the rubbed portion near ~8:00 is 4.453", i.e. shallower by 0.025" and 0.037", respectively, than they should be.

At the right of the first composite is another case that shows the tool bit machined the case over most of OutC but didn't touch part of it. The machined region is 4.484" deep and the untouched region is slightly deeper at 4.488". Along with the untouched region of the case at the left of the composite that's 4.465", this indicates variations in the castings were ~0.02" which sometimes placed the back face slightly further back than the reach of the cutting tool for OutC.

I rechecked the spacing between Gear B and the spline as shown in the third photograph of my previous post. The two T-types were 3.774" and 3.778" and the one Standard type was 0.061" shorter than the average of those two at 3.715". Since Gear B is a press fit there is room for a few thou. variation in these measurements between different layshafts. I also found a bare Standard layshaft and measured the distance shown in the second photograph as 3.680". This implies a bare T-type layshaft would be 3.690+0.061 = 3.751" so it's probably specified on BSA's production drawing as 3.750". Which means it's a reasonable guess that the 0.061"+/-0.002" difference I measured for the depth of InC, and for the Gear B-to-H difference, is actually on the drawings as 0.0625", i.e. 1/16".


Attached picture Gearbox_NoRecess02.jpg
Attached picture Gearbox_StdLayshaft.jpg
Posted By: old mule

Re: 1957 BSA Spitfire Scrambler - 12/08/18 4:32 am

Thank you- letting you know that this has been a valuable thread to read, thank you.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/08/18 5:42 pm

Originally Posted by old mule
letting you know that this has been a valuable thread to read, thank you.
Thanks for taking the time to comment. The 'Gearbox' tab of my 3.25"-inch (800-page) Gold Star 'Shop Manual' has copies of everything I've ever found about these gearboxes, but the further I went into the SCT2 the more I realized that detailed information on them was lacking. Some people may know everything that has been in this thread, but such knowledge is useless as well as easily lost to future owners if it's not made available to others.

I decided that more precision would lead to more understanding so I checked the calibration of my 4"-5" micrometer and then measured the distance from thrust washer #73 to the raised ring near the ID of Gear H for two T-type layshafts, as shown in the photograph. One is 4.5685", and the other is 4.5760", for an average of <4.5723">. Call that 4.572+/-0.004". Remembering from an earlier post, InC is 4.580+/-0.002". To the extent these small number of data points might be representative, this means we can expect the face of Gear H to sit ~0.008" below the face of the main housing. Even if the tolerances conspire against us, it still will sit ~0.002" below the face.

Also remembering from another earlier post, I found that when #74 is placed on the middle gearbox housing it sits from 0.006" below the surface to 0.0015" above the surface. Call that on average 0.002+/-0.004" below the surface. So, just considering averages, the average T-type layshaft will have an end float of 0.010" (4.580-4.572+.002=0.010) if installed with no gasket, and 0.020" if installed with a paper gasket, i.e. either way would have the desired end float. Actually, almost certainly BSA intended for #74 to sit precisely level with the face, in which case the end float would be 0.018" if installed with a paper gasket.

Of course, it's unlikely any set of components will have these average values, but this information is still quite useful. We can infer from it that BSA intended that the depth of InC in the main gearbox housing, plus a paper gasket, would provide the desired end float. Actually, I infer that their 0.010"-0.020" range isn't so much "desired" as it is an admission of BSA's production tolerances. So, given the choice, I would aim for the bottom end of this range. This information also says that something is amiss if we find Gear H above the face of the housing rather than slightly below since in that case only an out-of-spec fat paper gasket would provide the required end float, which isn't how it would have left the factory.


Attached picture EndFloat01a.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/09/18 4:04 pm

Possibly bringing this digression into gearboxia arcania to an end, a simple procedure to determine and adjust layshaft end float in T-type gearboxes prior to applying anything messy to the cases is as follows (a note about Standard gearboxes follows at the end):

Determining and Adjusting Layshaft End Float

To have everything in one place for what follows the internals of T- and T2-type gearboxes are shown in the first image.

1) Assemble the layshaft with thrust washer #73, but without #74, and measure the length with calipers to confirm it is approximately 4.570"+/-0.005"
[Although a micrometer is shown in the second photograph calipers are sufficiently accurate for this measurement that will determine if anything is seriously amiss in the way it has been assembled (e.g. Gear B not pressed fully on the shaft, pressed on without the locating ring in place, or is the thinner one from a Standard gearbox). Any problems need to be located and corrected before proceeding. Although Gears D and F interchange between T-type and Standard you still have to confirm they have the correct number of teeth for your intended ratios.]

2) Insert assembled layshaft into housing with thrust washer #73 but without #74

3) With a flat on the gearbox case use a feeler gauge to determine the Clearance to Gear H (CGH).
[If CGH is negative there is likely a problem with the housing (e.g. the needle bearing isn't flush with the case or the bearing is installed in an unmodified Standard case) or layshaft (e.g. there is an incorrectly made aftermarket washer in place of #99). Any problems need to be located and corrected before proceeding. For the layshaft and gearbox case shown in the third photograph CGH = 0.010". Note, however, that gasket residue or nicks in the Al can give an apparent reading a few thou. too high if you're not careful, and a slightly raised bush inside Gear H can give an apparent reading a few thou. too low if the feeler gauge is positioned over it rather than the raised machined surface on the gear. Also, since the layshaft is supported only at one end at this point it can be slightly tilted so measurements should be made in several positions and averaged.]

4) With thrust washer #74 in place use a flat and feeler gauge to measure the Clearance on the Middle Casting (CMC), keeping in mind it could be either positive or negative.
[For the casting shown in in the fourth photograph CMC = 0.005". If CMC is much larger than this it is likely the casting has been altered in which case a thicker bespoke washer may be required, and if CMC is proud of the surface by more than a few thou. it is likely due to an out-of-spec. aftermarket washer that is thicker than 0.113". Any problems need to be located and corrected before proceeding.]

5) Keeping track of positive or negative signs, calculate the Raw End Float (REF = CGH + CMC)
[For the combination shown in the third and fourth photographs REF = 0.010"+0.005" = 0.015". This says if the two cases are clamped together without a gasket the end float would be 0.015".]

6) Use REF to determine what additional layshaft shim, if any, or gasket thickness is needed to obtain the Desired End Float (DEF) of 0.010"-0.020".
[As can be seen from the fifth photograph, when the above two cases are bolted together without a gasket the measured end float is 0.016". This is the same as the 0.015" from the separate casting measurements within the variation expected from using feeler gauges. So, if this combination of layshaft and cases were to be used, these two cases should be sealed only using gasket cement to result in a value within the range of DEF.]

The situation of the REF being less than the DEF can be easily addressed with paper or composite gaskets. However, I can't remember ever seeing a discussion of what to do if the REF is larger than the DEF since washers #73, #74 and #99 only were made in one thickness each.

Although #73 and #74 are hardened steel, keep in mind that one side each sits directly against soft Al, and the equivalent of these hardened steel washers in a Standard gearbox are the soft (compared with hardened steel) bronze brims of the top hat bushes. Since none of these relatively soft surfaces has a wear problem it means the thrust against them is small. So, if needed, I wouldn't hesitate to make a #73 or #74 (but not #99) thrust washer from bronze of the necessary thickness to achieve the DEF.

For bespoke thrust washers I would use a high strength phosphor or aluminum bronze because there's no reason not to, although light duty SAE 660 bronze probably would be fine. Ideally, they would be surface ground to make their faces accurately parallel. However, it is very unlikely the brims of the top hat bushes in a Standard gearbox are accurately perpendicular to the layshaft, and they don't have problems, so the tolerance of a lathe should be fine for producing these washers.

Note on Standard type gearboxes: In these gearboxes the brims of the top hat bushes serve the shimming function of washers #73 and #74 so the end float procedure described above applies with this in mind. In Step 1) the measurement should be 4.400"+/-005" for a Standard layshaft.


Attached picture Gearbox_shims.jpg
Attached picture EndFloat01a.jpg
Attached picture EndFloat01.jpg
Attached picture EndFloat02.jpg
Attached picture EndFloat03.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/10/18 2:45 pm

Before leaving the subject of end float, I started assembling the Spitfire's gearbox yesterday and one of the first things to do was to check and adjust the end float. I did a test assembly and found it out of range at 0.026" without a gasket, making me initially think I'd have to machine a thicker thrust washer from bronze to reduce it below 0.020". I then realized there was another, even better, option. The first photograph shows Gear B pressed up against the circlip that locates it. Looking closely it can be seen that the groove for the circlip is considerably wider than the circlip, allowing another way to reduce the end float.

If a ~0.014" gasket is added the 0.026" end float would increase to 0.040" which is way out of range. However, if I added a wire to that groove the gear could not be pressed as far onto the shaft and the result would be to extend the far end of the layshaft further from the gear, i.e. it would reduce the end float. A 0.039" wire along with a gasket would reduce it to ~0" if the gear currently were pressed fully on and if it were then pressed back on with the same force after adding the wire. Actually, because the dogs on the gear are somewhat tapered on the bottoms, a wire of diameter less than that of the circlip would let the gear be pressed further than calculated from the wire diameter alone so this wire should result in a positive end float. It seemed worth spending a few minutes with various wires to find the best result.

The second photograph shows the shaft after I pressed the gear partially off. As my first attempt I added an additional "circlip" of 0.039" stainless steel wire, the thickest that would barely fit in the groove. The third photograph shows it after I pressed the gear back on.

The fourth photograph shows that after adding this wire the end float, with gasket now in place, has been reduced to 0.015". I expect after bolting the case together this may reduce by a thou. or two. Anyway, with the end float adjusted I can move on with assembling the gearbox.


Attached picture Layshaft_offset01.jpg
Attached picture Layshaft_offset02.jpg
Attached picture Layshaft_offset03.jpg
Attached picture Layshaft_offset04.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/11/18 5:24 pm

A few years ago I turned a broken gearbox case and middle cover into Swiss cheese so I could see what was going on inside. In light of the measurements I made over the past week, yesterday I made a slight modification to convert it into a precision instrument for inspecting the operation of T-type internals. It does the same for Standard internals with an appropriate spacer.

Anyway, the five photographs show the configuration of the gears in my SCT2 in each of the positions of the shifter cam in the order 1st, N, 2nd, 3rd, 4th. Enjoy flipping through the images and watching what each gear does as you shift up and down. Gears G & H are nearly hidden in these photos but can be easily seen by moving one's head, as can be seen that gear pairs A & B, and G & H are always in full contact with each other.

Less than full contact occurs with the middle set of gears in 2nd and 3rd. This contact is determined by the cam along with the fact each fork moves a pair of gears together coupled with the need for the dogs of one set of gears to be sufficiently engaged to transmit the torque while simultaneously those of another set are sufficiently clear of each other.


Attached picture Cutaway_gears_1st.jpg
Attached picture Cutaway_gears_N.jpg
Attached picture Cutaway_gears_2nd.jpg
Attached picture Cutaway_gears_3rd.jpg
Attached picture Cutaway_gears_4th.jpg
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 12/11/18 7:27 pm

Hi MM,

I'm not familiar with the SCT2 gearbox as used on your Spitfire Scrambler, however it looks similar enough in operation to the bikes I've previously worked on including Nortons, BSA's and others.

Your gearbox looks to be in good condition with little if any wear on the engagement dogs and gears. Whats not obvious from the photos is the condition of the cam plate, selector forks and detent spring, though no doubt you have these components under control and are using the best available.

If your gearbox is anything like the one used on BSA unit singles, then the correct engagement of the detent spring with the cam plate is essential for correct gear engagement, the gearbox cutaway observation holes will be useful for checking this. Additionally the tension on the detent spring can affect the gear change operation though I'm not sure how this is adjusted on your box.

As previously noted, shimming of the gears is needed and ideally I would try to adjust things so that the dogs are engaged as much as possible although this may not always be possible.


Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/11/18 11:08 pm

Originally Posted by gunner
Whats not obvious from the photos is the condition of the cam plate, selector forks and detent spring,
Actually, what I had installed for those photos were the plate, forks and springs that are part of the ventilated case. However, the plate and forks are easy to swap so I will be doing careful measurements with the actual SCT2's components.

Originally Posted by gunner
Additionally the tension on the detent spring can affect the gear change operation though I'm not sure how this is adjusted on your box.
There's a bolt-type adjuster that sets the load on a spring and BSA suggests adjusting it such that one thread is left exposed.

Originally Posted by gunner
I would try to adjust things so that the dogs are engaged as much as possible although this may not always be possible.
The possibilities for making adjustments are less than might seem apparent at first. Gears A/B and G/H are fixed in their positions so once the end float is set there's nothing more to be done with them. The shifter forks lock C/E together and D/F together so each pair is forced to move in lock-step. Referring to the photographs in my previous post, you can see there is a small space between E and G in 3rd gear so a shim could be placed on the shaft to offset that fork a little to the right. However, if there were done, the dogs on C would then engage less with A when in 4th.

The cam plate is the one other place where there could be problems. If it were made incorrectly it might, say, shove a gear pair the correct distance one way in a given gear, but not far enough the other way in a different gear. I took a photo I'll use later, showing the differences between a 'normal' and a reversed cam plate, applied some Photoshop magic, and produced the composite photograph below.

The reversed plate (i.e. RRT2-type) is in green with its cam slots in red, and the Standard plate is overlayed on it at 50% transparency. Note that the slots match extremely well between these plates, which means the relative positions of the gear pairs would be the same. However, I haven't yet checked to be sure there are no issues with the SCT2's cam plate, such as the slots being identical but the notches for the detent being incorrect. All will be checked before it goes together, but I've had no garage time today and will have very little tomorrow..


Attached picture RRT2_cam_overlap.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/12/18 3:22 pm

This past weekend I decided to disassemble another T-type gearbox so I would have a complete set of photographs of the entire rebuilding process (plus another freezer baggie full of gearbox parts...). Although I've written what follows specifically for the T-type, the differences from the Standard type are small so the information should be of general use to anyone with a pre-unit swinging arm BSA model.

The disassembly follows in the next few posts, broken up by the five-image limitation per post, but eventually all the king's horses and all the king's men will put a coherent gearbox rebuild thread together again. Maybe...

There is one photo per numbered line item in what will follow in the next few posts. To avoid headaches with numbering I don't mention the photograph number in each line description (e.g. Step 7) doesn't explicitly mention the "seventh photograph") so the reader will have to figure out that the, say, 2nd photograph in a given post goes with the 2nd Step in that post (again, for example, Step 7 will be in the 2nd post and will be illustrated by the 2nd photograph in that post because 7-5=2). Clear?

Disassembly of the Gearbox

1) The gearbox will be easier to disassemble if you mount it in a sturdy vise with soft jaws to protect the Al. Although it isn't essential to remove the inspection cover in order to disassemble the gearbox, the cover is held by two screws.

2) Remove the three screws and four nuts that hold the outer case. The arrows point to an additional screw and nut (hidden by the kickstart lever in this photograph), neither of which is removed. Also, leave the kickstart lever in place for the moment.

3) Rotate the kickstart lever somewhat to relieve pressure on its stop, then use the lever in that position to help wiggle the outer case off the four studs. A few gentle(!) taps with a soft mallet on the projection for the speedometer cable may be needed to help break the seal to the gasket. I'll deal with rebuilding this outer case sometime in the future so for now set it aside.

4) Flatten the lock washer on the drive sprocket, hold the sprocket with a chain wrench, and use a punch to loosen the nut. Since hitting the nut also in effect hits the ball bearing, instead of a punch I use a sprag socket I made for this purpose along with an impact wrench. Usually the chain wrench isn't needed when the impact wrench is used. Leave the sprocket in place for now.

5) Use a large screwdriver to shift the gearbox out of neutral into any gear. You may have to rotate the gearbox's input while doing this to get the gears to align and allow the shift to be made. Unless a reverse shifter plate is used (e.g. in an RRT2) neutral is engaged when the red recessed dot on the shifter quadrant is aligned with the recessed dot on the housing when viewed straight on. However, likely by now the paint is long gone; the red paint you see in this photograph was applied by me.


Attached picture Disassembly010.jpg
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Attached picture Disassembly050.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/13/18 3:55 pm

6) Remove the circlip from the end of the layshaft.

7) Bend the lock washer on the mainshaft flat and, with a chain wrench on the drive sprocket, remove the nut. An impact wrench makes this easier but, unlike when removing the nut on the drive sprocket, you will need a chain wrench to hold the mainshaft.

8) Remove the ratchet mechanism, spring, and washer.

9) With a large screwdriver lever the shifter quadrant back into neutral, which is where the recessed dots on the shifter quadrant and on the housing align when viewed straight on. For a reverse shifter plate (e.g. in an RRT2) move the shifter quadrant to its highest position (1st gear), then move it down one click to be in neutral. You can confirm any gearbox is in neutral by checking that the the input shaft and sprocket turn independently of each other.

10) One screw at the top still holds the middle cover in place but it is often hidden by the gasket and so easily can be missed. With the "hidden" screw removed, slide the middle cover off the four studs.


Attached picture Disassembly060.jpg
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Attached picture Disassembly090.jpg
Attached picture Disassembly100.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/14/18 3:17 pm

11) With the middle cover removed, slide the mainshaft out of the case. The drive sprocket now can be removed as well since the chain wrench won't be needed for the remaining disassembly.

12) Remove the selector shaft by first removing the grub screw and then pulling the shaft out from the front of the case. Since the grub screw seats in a deep groove in the selector shaft it is safest to remove the screw completely before trying to remove the shaft. Although the shaft may be a tight fit you can easily tap it out from the back of the gearbox using a drift.

13) With the selector shaft removed you can now remove Gears C and E along with the selector forks. Although the two selector forks were identical when new, because of wear it's best to mark them in some way so you can return them to their original positions when you reassemble the gearbox.

14) The complete layshaft with its thrust washers at either end can be removed as a unit.

15) If you want to remove the shifter cam plate, first remove the indexing plunger. Although an RRT2 has its indexing plunger installed at the top of the case rather than the bottom, all five T-type cases I have (for SCT, SCT2, ASCT, and STDT) are drilled and tapped at the top as well as the bottom so this feature of the main case is not unique to the RRT2.


Attached picture Disassembly110.jpg
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Attached picture Disassembly150.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/15/18 3:47 pm

16) Since the selector shaft already has been removed the cam plate now can be simply pulled off the short pin. It's best to remove this plate even if you only wanted to remove the plunger since otherwise it easily could fall to the floor when you handle the case. A nut with lock washer on the outside of the case holds the pin in place, and a slot in the head allows use of a 90° screwdriver to keep the pin from turning as the nut is removed.

17) Remove the snap ring and then the oil seal. Using two screwdrivers allows one of them to pry the notched end of the snap ring out of the groove and the other to lever it up and over the edge of the case.

18) If the sleeve bearing needs replacement heat the case to 225 °F and tap or press the bearing out with a socket or drift of suitable diameter. The press fit at room temperature is ~0.002" so, as shown in the inset, if you do not heat the case there is a good chance you will ruin the case by the force required to remove the bearing.

19) If the layshaft needle bearing (or bush) needs replacement it also should be done with the case heated to 225 °F. If the bearing is of the open-end type there's a big enough gap between it and the end cap that a 17 mm blind bearing puller can be used. If it is of the closed end type the bearing and the outer cap will have to be tapped out from the inside using a suitable drift.


These 19 steps complete the disassembly of the major components of the swinging arm-type gearbox, although several posts sometime in the future will be needed to address the middle and outer covers. As I wrote earlier, in parallel with these posts I've been pulling together into a Word document all the relevant material I've written on gearboxes and organizing it in a more logical sequence than in this thread. However, that document already is up to 68 pages, including 111 embedded thumbnail images, so how to deal with it after it's finished is an open question.


Attached picture Disassembly160.jpg
Attached picture Disassembly170.jpg
Attached picture Disassembly180.jpg
Attached picture Disassembly190.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/16/18 3:33 pm

Section I, the 19 steps to disassemble a pre-unit swinging-arm gearbox, was just completed. Next will be Section III, the steps needed to assemble one. I'm skipping Section II for now, the steps to inspect and repair all the internal components, because I've already covered some of this in posts spread over the past few years, and all of which will be in the final massive document. Anyway, what follows assumes all the necessary repairs already have been made and the components are ready to be reassembled.

As with the disassembly, there will be five photographs in each post, each illustrating the corresponding step.

Addendum: I realized I left out a description of the installation of the sleeve gear oil seal, which is now step 0 below. However, I can't add an image for this step because of the 5 images/post limit so instead refer to the final post of the disassembly process.

Assembly of the Gearbox

0) Follow step 17 of the disassembly in reverse to install the oil seal.

1) With the gearbox housing mounted in soft jaws on a vise, oil the bearings and the various components as they are installed.

2) Although the inside face of the sleeve gear is pulled tight against the inner race of the bearing, any oil that gets past can find its way out of the gearbox via the splines. Although this leakage path is unlikely, a thin coat of gasket sealant makes it even more unlikely.

3) Push the sleeve gear into place. It will be a snug fit so it might have to be lightly tapped into place with a piece of wood. Install the sprocket, lock washer and nut.

4) There is no torque specification for this nut but later BSA manuals specify 50/55 ft.lbs. for the 1" fork cap nuts. Based on this I torque the nut to 60 ft.lbs. using the sprag socket I made along with a chain wrench. Without such a socket you will have to use a hammer and drift. Once the nut is tight bend the lockwasher to lock it in place.

5) If the short spindle for the cam plate was removed, reinstall it with its lockwasher and nut on the outside, using a 90-deg. screwdriver to keep it from turning, if necessary. Once the nut is tight bend the lockwasher to lock it in place. Slip the cam plate on the spindle, check that it rotates freely, then move it to the neutral position (CCW to the first detent, then CW to the shallow neutral detent next to it) and install the plunger.


Note: PhotoShop, Adobe Bridge, Paint3D, and Windows all show the photographs in the correct orientation but Britbike has rotated all of them in this post by 90 degrees. I don't know why this is the case and have no control over it..


Attached picture Assembly010.JPG
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Attached picture Assembly040.JPG
Attached picture Assembly050.JPG
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 12/16/18 6:54 pm

Great work MM and just a couple of comments which may be useful:-
- the gearbox sprocket looks slightly hooked to be, maybe its the camera angle or you're using an old sprocket for demo purposes.
- there's clearly a line on the selector cam where the detent spring has been rubbing. Its often worthwhile reliving any high spots in this area and also inside the selector grooves. This will help make the gear change smoother.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/16/18 8:45 pm

Originally Posted by gunner
gearbox sprocket looks slightly hooked ... a line on the selector cam
You're right on both counts. But...

As I assembled the SCT2 gearbox (which already is finished, although I've only posted the first five steps so far) I made notes. Sometimes I took photos of certain steps on the SCT2 as soon they happened, other times my hands were too greasy to use my iPhone so an hour or two later I consulted my notes and used parts from the shelf to reconstruct those earlier steps, and yet other times I realized when drafting the material that an additional, or a different, shot would be better and I reconstructed it. Anyway, what you see isn't (necessarily) what the SCT2 got.

An unedited example of a scene I reconstructed today from non-SCT2 parts to better illustrate a step I took a few days ago when assembling the SCT2 is below. Getting the shifter fork to capture Gears C and E as well as insert in the shifter plate can be a fiddly process which sounds even more complex than it is when described in words. So, I reconstructed the scene from another point of view to make it clear what the words mean. An edited version of this shot will appear in a few days when the post reaches that point in the assembly.

A very distressing development just occurred while I was typing this. I got a text from the organizers saying that the 2020 Cannonball will be for pre-1930 motorcycles. Which means my 1928 Ariel again qualifies. Damn, so much for the hoped-for excuse that a different machine would be needed...

Attached picture IMG_9768.JPG
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 12/17/18 12:17 am

Quote
A very distressing development just occurred while I was typing this. I got a text from the organizers saying that the 2020 Cannonball will be for pre-1930 motorcycles. Which means my 1928 Ariel again qualifies. Damn, so much for the hoped-for excuse that a different machine would be needed...


Well, at least you now know the Ariels weak areas and have the time, patience and skill to address them.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/17/18 5:09 pm

Note: this post only has 4 steps in it because step 10 will have two photographs and I don't want the 5 photograph limit per post to break them up.

6) If a reverse cam plate is installed instead of a standard one, rotate it CW to the first detent (to the right of the shallow neutral detent) which is 1st gear and install the plunger at the top of the gearbox rather than the bottom.

7) Screw the plunger in such that it leaves one thread exposed after tightening the lock nut.

8) Install the complete layshaft assembly along with the shifter fork in the orientation shown and with the fork overlapping the facing raised ridges of Gears D and F. The round projection on the side of the shifter fork facing the shifter cam should be in the slot of the cam farthest from you. This photograph shows Gear H and thrust washer #74 on the layshaft, but they should be removed for the next step. Leave washer #99 in place or, if you remove it, do not forget to replace it.

9) With Gear H and thrust washer #74 removed from the layshaft, push Gear C all the way against sleeve Gear A as well as against the housing at the left (i.e. not directly in line with sleeve Gear A), and hold the second shifter fork in the position and orientation shown to allow clearance for the raised ridge of Gear E in the next step.


Attached picture Assembly060.jpg
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Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/18/18 3:17 pm

This post only has four steps because the first two photographs go with step 10, leaving only three more that can be included.

10) While continuing to hold the shifter fork with your right hand in the position shown in step 9, use your left hand to insert Gear E, push it against Gear C, then lower the shifter fork to capture the adjacent raised ridges of Gears C and E. After the fork has captured the two gears it might require a small manipulation to ensure the round projection on the opposite side of the fork is seated in the cam slot nearest you. I realize this operation sounds fiddly, and it can be, but it's fairly straightforward if you follow the instructions. The first two photographs in this post illustrate step 10 as you will see it, and if you could look down through the top of the case before the fork is fully seated in the cam.

11) When both forks and the shaft are correctly installed, ensure washer #99 is still in place on the layshaft and then replace Gear H and washer #74.

12) Insert the mainshaft and then insert the selector fork shaft through the two forks, which will require moving each slightly to align them as you insert the shaft.

13) You might have to tap the shifter shaft to get it fully into the housing, which is when the end is flush with the outside. If you overshoot, tap the shaft back to be flush with the housing. Then put Loctite on the retaining screw and tighten it to lock the shaft in place. In addition, you could fill the cavity above the screw with silicone sealant to be extra careful since if the screw vibrates loose the shaft could migrate out causing the gearbox to cease shifting.


Attached picture Assembly100.jpg
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Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/19/18 2:40 pm

14) Confirm the shifter cam plate is still in neutral. Then, in a test fitting, install the middle cover using the screw at the top and a spacer on the stud diagonal from it to tighten it. Use whatever gasket (or none) that you used previously to set the end float of the layshaft. It's OK to let the shifter quadrant find its own position in this test. Make sure the shafts rotate freely.

15) Measure the end float to confirm it is still the same value as you previously determined. If not, find the problem and address it. The end float should be in the range 0.010"-0.020".

16) Remove the middle cover, apply gasket sealer to the surfaces, wait whatever time is recommended by the manufacturer (20-30 min. for the Permatex 'Permashield' that I use), install the gasket, and slide the middle cover partially on, leaving a gap of a bit over ÂĽ" from the main case.

17) With a standard, non-reverse, cam plate that is in the neutral detent, hold the shifter quadrant with the two dots aligned when viewed straight on.[*] Use a soft mallet to gently tap the middle case to lower the gap to a bit less than ÂĽ" at which point the teeth of the shifter quadrant will start to mesh with those of the shifter cam. You might have to move the quadrant slightly up or down to get the teeth to mesh. After confirming the two dots are still aligned tap the cases together. If the dots are not aligned while there is still a gap, widen the gap enough to release the teeth, re-align the dots, and try again until you are able to install the middle cover with the dots aligned.
[*]BSA Dealer Parts and Service Bulletin No. 82 dated 19 March 1963 says an unknown, but small, number of shifter quadrants were produced with the dot in an incorrect position which could result in not being able to select all four gears. The Bulletin says there isn't "any way of accurately describing how the quadrant might be checked". Because of the rounded outer edges of the quadrant it's not possible to give accurate figures but when using calipers I find the center of the dot 0.25"+/-0.01" from the nearest edge and 0.65"+/-0.1" from the other edge.

18) If a reverse cam plate is installed the dots are not used. Confirm that the reverse cam is in the 1st gear detent, move the quadrant up until there is a ~5 mm gap between it and the case, and tap the case to lower the gap to less than ÂĽ" at which point the teeth will begin to mesh. If correct, the gap between quadrant and case will be ~5 mm as the teeth start to mesh but if off by a tooth it will be ~12 mm. After the case is fully in place the gap will be nearly zero as the teeth are fully meshed but if off by a tooth the gap will be ~7 mm.


Attached picture Assembly140.jpg
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Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/20/18 4:23 pm

19) Once the quadrant and cam are correctly meshed tap the cases together and clamp them with the screw and a spacer on one of the studs.

20) Before the gasket sealer has set, use a large screwdriver to shift the gearbox up and down through the range to confirm it clicks into five detents total (four gears plus neutral). If you have the inspection cover off you can watch the operation of the two pairs of gears as they are moved by the selector forks.

21) Attach the circlip to the end of the shifter shaft.

22) The end float should not have changed, but confirm it still is within the range 0.010"-0.020".

23) Use a large screwdriver to put the gearbox in any gear and install the kickstarter ratchet assembly. In order from inside to out this consists of a washer, bush, spring, pinion, ratchet, lock washer, and nut. Based on the thread being 9/16" I use a chain wrench to hold the sprocket and torque the nut to 40 ft.lbs. Once the nut is tight bend the lock washer to lock it in place.


Attached picture Assembly190.jpg
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Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/21/18 4:16 pm

24) Install the kickstarter quadrant in the middle cover and make sure the mechanism operates smoothly since wear of the second tooth of the quadrant can cause it to jam (the first tooth is partially ground off) and a too-tight bush under the ratchet pinion can cause it to bind.

25) Install the kickstarter quadrant in the outer cover with the notch hooked over the spring.

26) If you removed the nut for the kickstarter spring or the special fastener for the speedometer drive, replace them now. The speedometer drive mechanism has to be correctly oriented in the housing in order for the unthreaded portion of the fastener to pass through it to keep it from rotating.

27) Do a test fitting of the outer cover to make sure there are no issues. Install the kickstarter lever, tension it against the spring to the ~10:00 position (~12:00 for the RRT2-type quadrant) for the lever to clear the stop, and fit the outer case over the four studs. This may require wiggling the kickstart back and forth as well as rotating the mainshaft to allow the speedometer gears to seat.

28) If all went well with the test fitting, remove the outer cover, apply gasket sealer to the surfaces, and wait whatever time is recommended by the manufacturer (20-30 min. for the Permatex 'Permashield' that I use).


Attached picture Assembly240.jpg
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Posted By: gavin eisler

Re: 1957 BSA Spitfire Scrambler - 12/22/18 1:41 am

29) Shout Hurray. and take a dram.

Well done MM
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/22/18 3:20 pm

Originally Posted by gavin eisler
29) Shout Hurray. and take a dram.
Not so fast, buckaroo, there still are two steps remaining:

29) Reinstall the cover as in step 27. Four nuts with washers along with three screws (two 2" at the front and one 1â…›" at the rear) hold it in place.

30) Install the circlip shown by the arrow followed by the selector lever and check that the gearbox correctly selects all the gears. If you removed the drain plug or inspection plate during the rebuild now would be a good time to reinstall them.

These 31 steps (counting step 0 that I added later) complete the assembly of the major components of the swinging arm-type gearbox, although several posts sometime in the future will be needed to address the middle and outer covers.


Surely the effort that went into these gearbox posts deserves a double dram.


Attached picture Assembly290.jpg
Attached picture Assembly300.jpg
Posted By: gavin eisler

Re: 1957 BSA Spitfire Scrambler - 12/22/18 8:27 pm

Definitely. Slainte.
Posted By: NYBSAGUY

Re: 1957 BSA Spitfire Scrambler - 12/23/18 1:49 pm



Sláinte mhaith*, MM!

THis was well worth the double dram, which I will raise myself this evening. It has inspired me to start the restoration of my own 59 DBD34 scrambler with the gearbox, and I'm already into the middle cover.

Relax, now, and dream of Cannonballs.



*Gaelic: "Good health!" as spoken by the Celts in Gavin Eisler's world, and in mine, across the water.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/23/18 11:56 pm

Originally Posted by NYBSAGUY
Relax, now, and dream of Cannonballs.
Should I dream of small or large Cannonballs?

For the past week I've been at an impasse of sorts with the Spitfire. With the rebuilt gearbox resting comfortably it would seem the engine should be next. However, once I start on it the workbench will be occupied for the duration and I'd like to get the Ariel's engine taken care of first. Unfortunately, the backordered exhaust valve blank still hasn't shown up. I'll reassess my options with the Ariel's head and the Spitfire's other components (e.g. rebuilding the forks) over the next few days and decide what to do next.

While straightening up the work area today I decided to lay out all the "special tools" I used in rebuilding the SCT2 gearbox (i.e. excluding screw drivers, sockets and spanners). Unless I forgot something, the 20 I used are shown below.


Attached picture SpecialTools.jpg
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 12/24/18 7:23 pm

Before you fit the gearbox to the frame it may be worthwhile filling it with oil and leaving it for a few days or weeks with a sheet of white paper underneath. If any leaks appear they should be easier to fix than with it mounted.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 12/25/18 5:20 pm

Originally Posted by gunner
it may be worthwhile filling it with oil and leaving it for a few days or weeks
That's an excellent suggestion which I've now followed myself since the gearbox was currently sitting on the shelf doing nothing. I bolted it back on the stand and filled it with 400 mL of 40W AeroShell that I had sucked out of the Ariel's tank when I removed it from the bike. It's not that I was afraid to use 20W for this test, but I will be switching the Ariel to Valvoline VR1 when it's back together again and I have no plans for the remaining few quarts of "ashless" AeroShell. Although oil only has been it for less than 24 hours so far, when I sneaked out to look at it the paper towel under the gearbox was still dry. So far, so good.

The photograph shows that you can check for the correct amount of oil by looking through the inspection cover. With 400 mL the oil level will be at the top of the layshaft (the oil on the mainshaft is there because I tilted the gearbox by 45° to fill it).


Attached picture OilLevel.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/01/19 5:25 pm

A week ago I wrote about the gearbox:
Originally Posted by Magnetoman
I bolted it back on the stand and filled it with 400 mL of 40W AeroShell
After seven days there isn't even a drop of oil on the paper towel below the gearbox so I'm declaring it leak-free. I'll drain the AeroShell from the gearbox and set it aside.

Over the past week I was only in the garage to retrieve a pair of motorcycles to ride with my younger daughter who was in town for a few days and to grab tools and supplies for a project with a granddaughter. However, the holidays are over so it's time to get back to work because the Spitfire isn't going to restore itself. A cold front has settled in and it got down to freezing last night, but I've already braved the frigid air this morning to go to the garage to switch the thermostat from 'cool' to 'heat'. By the time the coffee has kicked in it should be up to a civilized working temperature.

My plan for the day is to mount a 3-jaw chuck on the Sunnen hone and see if the FC-E external hone (range 0.80"-1.50") can return pitted fork tubes to service. I have coarse and fine stones for it and, in principle the fine stone is capable of producing a 2 µin. finish on soft steel so, beyond the reclamation aspects, use of this external hone should be a good way of making seals last longer on otherwise-good fork tubes. The seals in my BB and Catalina Gold Stars are showing signs of weeping so, um, honing my technique on decrepit tubes will have me ready to work on good ones.

I'm not sure how far I'll get today because first I'll have to fabricate a mandrel to hold the inexpensive Chinese 3-jaw chuck I bought for this purpose (Sunnen's mandrel-mounted chucks sell for $300+ on eBay). Unlike a lathe, precision isn't required for this purpose so the accuracy of the Chinese chuck will be fine.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/02/19 4:49 pm

Originally Posted by Magnetoman
I'm not sure how far I'll get today because first I'll have to fabricate a mandrel...
I only got as far as fabricating the mandrel. I've had the chuck for a while but, having not thought of an easier way of mounting it, yesterday I gave up and machined away 12.3 in.3 of Al from a 3-1/4" bar to create the mandrel. With that out of the way, today I'll see how well this works on a rusty fork stanchion.

I may have to rig some sort of center to support the far end of the stanchions as they rotate, but maybe not. The way an external hone is used it and the operator act as a sort of "steady rest." Also, although Sunnen's charts show 500 rpm as the optimum speed for something of the diameter of a stanchion, the pulleys in my hone go down to 200 rpm so I'll start out at that speed. The foot pedal allows running at even lower speeds and further acts as a dead man's switch should the 5 lb. (est.) piece of spinning metal get out control. A slower speed only means it will take longer to do the honing, but the shop foreman hasn't fired me yet for my low productivity so that will be OK.


Attached picture Sunnen02.jpg
Attached picture Sunnen03.jpg
Attached picture Sunnen04.jpg
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 01/02/19 10:02 pm

Quote
see if the FC-E external hone (range 0.80"-1.50") can return pitted fork tubes to service.


Will be interesting to see how this works out, with pitted chrome fork tubes as used on later bikes the DIY fix used years ago was to fill the pitting with epoxy and sand down with wet & dry until all was smooth again. This approach seemed to work for those folk that tried it.

With your original fork tubes I assume the pitting is more rust related rather than stone chips so hopefully the pitting is shallower and easier to rectify.

Perhaps an alternative approach would be to simply spin the fork tubes in a lathe and use ever finer strips of emery cloth pulled up tight around the seal area to remove pitting and achieve a smooth surface.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/03/19 5:50 pm

Originally Posted by gunner
Perhaps an alternative approach...
Clearly you're forgetting the well-known maxim: if your only tool is a Sunnen hone, every problem looks like a nail. Or something like that.

Originally Posted by gunner
simply spin the fork tubes in a lathe and use ever finer strips of emery cloth pulled up tight around the seal area to remove pitting and achieve a smooth surface.
Based on yesterday's experiments, and the appearance of a shelf-full of pitted BSA fork stanchions, it would take a long time to recondition the surfaces of most of them with a lathe and emery cloth.

Originally Posted by gunner
the DIY fix used years ago was to fill the pitting with epoxy and sand down with wet & dry until all was smooth again.
In essence I'm planning to try the same thing, except with silicon bronze applied with a TIG torch. Epoxy is a "temporary" fix that might only last decades whereas silicon bronze is permanent.

The first photograph shows a stanchion mounted in the "new" chuck with the external hone in place on it. What a static photograph can't show is the chuck holds it quite firmly while spinning at the 500 rpm recommended for honing something 1.25"-dia. There is no need for a center at the other end of the stanchion. So, the problem of honing the stanchions is solved. Except...

A restored motorcycle is the result of having repeatedly overcome obstacles only to reveal the next one, until finally there are no more obstacles left to overcome. At that point the motorcycle is done. Yesterday I overcame the obstacle of being able to install stanchions in my hone, revealing the problem of pits that are too deep to hone away. An example is in the second photograph.

To show what will be required of the hone the third photograph has an assembled set of Gold Star forks along with the relevant component parts. You can tell they are Gold Star forks by the forged mudguard brackets welded to the lower legs. As this photograph shows, only the region between the two arrows (i.e. between 13" and 18.5") needs to be pit-free and smooth for the oil seal whose position is marked on the separate seal holder. I had spun the exposed stanchion in the lathe to remove the superficial rust and grease with a Scotchbrite pad so the discoloration between ~16" and 18.5" is likely due to water that had made its way past the gaiter and sat trapped on top of the seal. Some of the discoloration is superficial, but in some places there are pits.

I should say I have an embarrassingly-large number of stanchions on the shelf, most still trapped under other things, so I may be able to mix-'n-match my way past this obstacle. I'll have to unload the shelf to find out. But, what if all of them have deep pits (quite possible), or when working on a bike where properly-made aftermarket stanchions aren't available (sadly, odds are that this may be likely as well)?

It would be relatively easy to fill in the pits with silicon bronze then turn back to size in the lathe before finishing in the hone. But, only if the stanchions are straight. Of course, they aren't. At least the three that I've tested so far aren't. When clamped at one end in the chuck and at the other end with a live center, the middle of the stanchions have a TIR of ~0.015". However, that overstates the problem a little. When clamped and centered in a 4-jaw chuck just past the bottom of the region that has to be smooth (i.e. ~19"-23" inside the headstock of the lathe) the top end of the smooth region has a TIR of only 0.0025" for this randomly picked stanchion, as shown in the fourth photograph.

To digress for a moment, my guess is when I take the time to measure some of these stanchions I'll find the bending is confined to between the bottom yoke and the lower end, caused by the weight of the bike. If so, it would be relatively easy to clamp the length above the bottom yoke flat and use a press to remove the bend in the lower part.

In the interests of science I decided to risk of ruining a presently-useless stanchion. With it still centered in the lathe I cut 0.004"-dia. from the area for the seal to remove all traces of pitting. To remove the machining marks I then honed it with a stone that a table in a Sunnen manual said should give a surface finish of 25 µin., followed for a short time with a finer stone that should have given 2 µin. The result is shown in the fifth photograph. I was running out of time by then so I stopped honing sooner than I otherwise would have so I would have time to wash up and measure the surface roughness. It was 22 µin, indicating I hadn't honed it long enough with the fine stone. However, even the current result isn't bad since Timken recommends a surface finish of 10-20 µin for their lip seals.''

There's also the matter of tolerances. Timken recommends a tolerance of +/-0.003" for the diameter of the shaft whereas the lathed and honed shaft is currently 0.014" smaller than a nominal 1.250". I say 'nominal' because the three that I measured are ~1.246", presumably to give 0.004" clearance for the fork bushes. Anyway, my experiment ended up reducing the diameter by 0.010", largely because the bit I used in the lathe periodically tore off a few thou. more than it should have to leave a surface that wasn't smoothe. I'll use a different bit next time.

Next I'll try filling some big, deep pits with silicon bronze before cutting on the lathe. Before someone asks why I don't just buy new stanchions, it's because I don't want to. A significant part of my enjoyment of restoration is devising solutions to problems like this one rather than buying aftermarket replacement parts. Even if those aftermarket parts turn out to be of good quality, which way too often they don't.

Question: The parts book shows different stanchions ("front fork shaft") for the Scrambles (89-5061) and Clubman (42-5027). What are the differences between them?


Attached picture Sunnen05.jpg
Attached picture Sunnen06.jpg
Attached picture Sunnen07.jpg
Attached picture Sunnen08.jpg
Attached picture Sunnen09.jpg
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 01/03/19 6:29 pm

Ahh, I didn't realise you were filling the pits with tig welded silicone bronze, that sounds like an ideal solution. The epoxy filler I mentioned as a repair is likely only a temporary solution and is something that has been going around the back street bodgers rumour mill for years, though I've never tried it.

If I had the time, money and space a Sunnen hone would be on my shopping list. As it stands I'm having to make do with an ancient long bed Randa lathe which might just about accommodate a fork tube, hence my comments on using emery cloth.

Happy new year !
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/03/19 7:24 pm

Originally Posted by gunner
filling the pits with tig welded silicone bronze, that sounds like an ideal solution.
I'll have to experiment with this to know if it will work as I hope. Applying heat is a common technique for straightening warped steel. Heat on the outside of a bend causes the metal to expand, making the bend temporarily worse, but when it cools it shrinks by more than it had expanded so it leaves the steel with less bend than it started with. My hope is that the melting temperature of the silicon bronze is low enough, and the heat input from the TIG torch is localized enough, that the bending it causes will be negligible. Only measurements and tests will tell if this is the case.

Note that I said in my previous post that I found the three tubes I measured all to be bent. That's a different thing than the bending that I hope doesn't happen with the silicon bronze. The current bends are in a specific direction, whereas the heat required to fill pits will be in random locations so if they cause their own bending the result will be a pretzel-ish tube.
Posted By: ducati2242

Re: 1957 BSA Spitfire Scrambler - 01/03/19 9:15 pm

Can tubes be made of a material that doesn't rust . Something like Ti tube or stainless . Or do they have to be made of steel and hard chromed . Might well be a daft question but if you don't ask and all that .
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 01/03/19 9:39 pm

Hi MM,
I would not risk "repairing" old stanchions with TIG braze
Pitting in the legs could lead to cracking in use, I do not believe filling with TIG braze is a "cure"
The preferred way to repair stanchions is to grind to remove pitting and hard chrome followed by final grinding to size
This I reserve for fork legs that are not readily available or massively expensive new.

BSA stanchions are easily available in standard or hard chromed with matched bushes
Only once did I get a poorly made set in the last 30+ years out of the many many sets I have fitted

Now if you come up with a method to resize the slider bores and hone down past the tapered plug, I am all ears

John
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/03/19 11:50 pm

Originally Posted by ducati2242
Can tubes be made of a material that doesn't rust .
It comes down to cost. To squeeze every penny out of production a manufacturer chooses the materials and processes that give acceptable results at the lowest cost.

Originally Posted by chaterlea25
Pitting in the legs could lead to cracking in use, I do not believe filling with TIG braze is a "cure"
The preferred way to repair stanchions is to grind to remove pitting and hard chrome followed by final grinding to size
I'm not at all worried about cracking. In principle every jagged rust pit, no matter how small and no matter where it is on the stanchion, is a stress riser. However, the stress is relatively small and anyway silicon bronze has essentially the same tensile strength as the steel so brazing the pits will eliminate the stress risers with something that has the strength of the base metal. What I don't know yet is if the heat will cause the tube to bend.

However, if the pitting is too extensive then grinding and building back up by plating would be the reasonable choice. However, there are limits, since if the pitting is too deep the depth of plating could exceed what can be done without risking delamination.

Originally Posted by chaterlea25
BSA stanchions ... of the many many sets I have fitted
Do you know the answer to my question about the difference(s) between the ones in scrambler vs. clubman forks?

Originally Posted by chaterlea25
Now if you come up with a method to resize the slider bores and hone down past the tapered plug, I am all ears
You're getting ahead of me. I haven't hit that obstacle just yet.
Posted By: Andy Higham

Re: 1957 BSA Spitfire Scrambler - 01/04/19 9:08 pm

That's the good thing about Velocette forks, the sliders are drawn seamless tube with the top and bottom parts soldered on
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 01/04/19 10:58 pm

Hi MM,
Does the scrambler have the 7in. single sided front brake fitted?
The right hand leg for the 7in. has a lug for the brake plate anchor
GS scramblers are extremely rare over here

John
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/05/19 1:52 am

Originally Posted by chaterlea25
Does the scrambler have the 7in. single sided front brake fitted?
The right hand leg for the 7in. has a lug for the brake plate anchor
My question is/was about the inside tubes, but now that you mention it the parts list show different R and L "sliding tubes" as well. Are you saying the lug in the first photograph (my Catalina, but the same as on my Special Competition) is different on a Clubmans? It seems it's time for a fork research project that I'll start on the Gold Star Forum.

Today I tested the practicality of using silicon bronze to repair pits in a fork tube. The tube I chose is badly pitted so chaterlea25's approach of grinding and replating to size would be appropriate to salvage it. But I wanted to know how much, if any, distortion would be caused by the TIG torch. The second photograph shows the original pit, after I ground away the discolored steel with a carbide bit, and after I had filled it with bronze.

The third photograph shows the bronze after I held the tube as close as possible to the brazed area in a 4-jaw chuck, centered to better than 0.0002", and removed all but ~0.001" of the bronze. I used Scotch tape (thickness ~0.001") to tell me when the bit was close enough. Presumably, at this point the Sunnen could deal with the rest, although I could have taken off another ~0.0005" without any risk of the bit touching the tube itself.

After removing the bronze in the lathe I repositioned the tube to clamp it in the same place as I did yesterday when I measured the bend. Using the same wide foot on the dial indicator as yesterday (to "average" over any pits it encountered) I measured the bend every 2" along the ~23" length of the tube. The bend was the same as before. So, this is a good technique for repairing a "reasonable" number of pits in a fork tube in order to reclaim it.



Attached picture CatalinaRightForkLeg.jpg
Attached picture ForkTube_bronze01.jpg
Attached picture ForkTube_bronze02.jpg
Attached picture ForkTube_bronze03.jpg
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 01/05/19 2:07 am


Sometimes it's the little things you learn, I would never have though of using tape to set the tool.

Rod
Posted By: chaterlea25

Re: 1957 BSA Spitfire Scrambler - 01/05/19 10:55 pm

Hi MM,
The slider shown in you photograph is for the 8in single sided hub or the 190mm
The slider for the 7in. brake has a cup shaped lug just above the rear lower mudguard mounting (cup open end to the brake plate)
a stub on the 7in. brakeplate locates into the cup as the spindle is tightened

I do not know why the stanchions are different?
Q1 are they longer to offer greater ground clearance, Are the springs different as well?
Q2, Are they heavier in wall thickness to add strength for off road ?

John
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/06/19 2:20 am

Originally Posted by chaterlea25
The slider for the 7in. brake ...
I don't think the 7" was too popular in the U.S., but I'll now look through the pile of fork legs to see if I have any. Thanks.
Posted By: BritTwit

Re: 1957 BSA Spitfire Scrambler - 01/06/19 2:28 am

I posted this earlier on the Gold Star forum. It may be useful here.

This is what I've found in the last few years examining the parts and researching parts books. I can verify when I get back to the shop.

Bottom yolk 42-5012 scr. is not drilled for the steering lock stop bolt
42-5015 Club. is drilled 1/4 CEI for stop bolts
At a later date 42-5015 was superseded to the 42-5012 as used on some A65's/B44

Fork shafts 89-5061 scr. has taper between the upper and lower fork clamps (clip ons won't work)
42-5027 club has the same diameter on the entire length of the fork (allowing clip ons to be secured)
Pre unit oil holes are vertical and unit are radial.

Fork legs 65-5410/5408 scr have the lug locator forging (Lower R/S) for the 7" hub brake plate and the L/S is different to accommodate the 7" hub axle.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/06/19 2:11 pm

Originally Posted by chaterlea25
I do not know why the stanchions are different?
Q1 are they longer to offer greater ground clearance, Are the springs different as well?
Q2, Are they heavier in wall thickness to add strength for off road ?
Originally Posted by BritTwit
I posted this earlier on the Gold Star forum. It may be useful here...
A little knowledge is a dangerous thing. I was in blissful ignorance about the Spitfire's front end until I started down this road to try to understand fork differences. Chaterlea25's question about fork springs caused me to look at the Hap Alzina bulletin that lists the differences of the Spitfire that aren't in the A10 parts books. The Alzina bulletin doesn't have a separate listing for the springs, only 42-5038 for the complete fork assembly, which doesn't correspond to either the DBD Scrambler or Clubmans in the UK-spec. parts catalog. However, the Spitfire's front mudguard and stays (but not the complete wheel) all are from the DBD catalog, and the U.K.-spec. Scrambler also had long outer sleeves and a number plate, so I'll speculate heavier springs to deal with the additional mass of the A10 engine resulted in the new part number for the complete assembly.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 01/06/19 5:21 pm

Don't assume BSA fitted heavier fork springs to heavier bikes, when you look at the spring rates fitted to the A65 and much lighter B25 the B25 got the heavier springs.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/06/19 6:07 pm

Originally Posted by kommando
Don't assume BSA fitted heavier fork springs to heavier bikes,
My speculation of heavier springs was prompted by running across Alzina's Service Bulletin #28 (11/10/59) describing "Setting up BSA Catalina and Spitfire Scramblers for the desert." Among the modifications to the forks it suggests installing side car springs. It also suggests plugging the top oil hole on the fork tubes and installing "Webco double acting fork dampening rods #1353." Presumably, in addition to making the forks wet, the "dampening" rods helped the handling. Precision equipment seems to have been lacking in some shops back then since the mechanic was to add 4 ounces of oil, or to the "bottom of the 'C' on a coke bottle." My oldest Webco catalog is 1961 showing these retailed for $10.95/pair at the time.


Attached picture Webco.jpg
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 01/06/19 9:40 pm

It's logical and normally works that way but there were exceptions, no idea why BSA did what they did as I fit the lighter A10 springs to the B25 but BSA fitted these stiffer springs to all the C15 completion framed bikes from 63 to 70.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/16/19 2:12 am

Although there are detail differences, pre-unit BSA forks from A(10) to Z(B34) are variations of the same basic design. While we're still sorting out just what those detail differences are, I turned my attention to refurbishing the Gold Star forks on my Spitfire.

About two weeks ago chaterlea25 wrote:
Originally Posted by chaterlea25
Now if you come up with a method to resize the slider bores and hone down past the tapered plug, I am all ears
What he's referring to is a ~5/8"-dia. pin that projects from the bottom of the lower legs as shown in the first photograph. The function of the pin is to insert itself in the hole in the plug at the bottom of the fork leg to significantly increase the resistance as the forks threaten to bottom. Because of this pin it's impossible for a hone to reach the bottom 2â…›" of the legs to refinish them. As an aside, measuring the diameter of a pin, let alone a tapered pin, that is located ~7" deep in a tube isn't easy. I dropped several collets of increasing size into the tube and 9/16" was the first one that fit over the top part of the pin.

Although there can be exceptions, a general principle that applies to most mechanical devices is that since someone assembled it, it can be disassembled (although, doing so may not be easy). Exceptions can include welded and crimped components. So, I examined the pin for evidence of how it is held in place. Although it might have been welded or brazed to the bottom cap before the cap in turn was welded to the fork leg, I assumed (incorrectly, as it turned out) that was unlikely because of the distortion welding causes. It seemed more likely that the cap was welded to the bottom of the fork leg, then the ID of the leg machined and finished for the bush, and finally the pin installed. Further, since there is no force on the pin in operation there's no reason it needs to be held any more firmly than a press fit, which is a less expensive manufacturing process than brazing. I could see no sign of brazing with my borescope (second photograph), making me increasingly confident in my -- incorrect -- assumption it was a press fit. However, before making a tool to remove the pin, it would be nice to be sure.

Last week I found a decrepit set of sliders on eBay for very little money and bought them rather than using one of the too-many I already have. Ebay showed a "guaranteed delivery" of this past Saturday so, confident in my (incorrect) assumption the pin is a press fit, I designed a tool to remove it and ordered the items I would need to make the tool. Despite it being "guaranteed," on Saturday eBay changed the delivery date to today, and this morning they changed it to Friday. I had waited as long as I could bear to so today I picked the worst of the legs I already had and sacrificed it. As the third photograph shows I used a slitting saw on the mill to slice open the bottom of a leg that was past its best-by date (although still salvageable, so I felt guilty dissecting it even if it was done in the name of science).

As the fourth photograph shows, the pin is not a press fit. The pin was machined into the bottom forging which then was welded to the tube. BSA counted on the end cap itself, with the ~0.075" thick section that projects 0.23" into the tube, to keep distortion at whatever they considered to be an acceptable level. Also shown in this photograph is the pin is 2â…›" long. The bottom ~1" is 0.62"-dia., tapering to 0.50"-dia. over the next ~1", and finally into a bull nose over the last â…›"

The fifth photograph is a detail of the area where the bottom forging is inserted into the tube and welded.

Although, one of the many pieces that came with the Sunnen when I bought it last year is a 1½" mandrel for blind holes, it isn't going to help with BSA fork sliders. I'll have to design something else to reach past that pin. The window I now have in this slider should help a lot with that.


Attached picture ForkTube_centralpin01.jpg
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Attached picture ForkTube_centralpin08.jpg
Posted By: R Moulding

Re: 1957 BSA Spitfire Scrambler - 01/16/19 5:07 am


MM, i'm far from a machinist so excuse my ignorance. Would it be possible to machine the cast lug from the tube and fabricate a replacement tube that could be welded on as per factory?

Rod
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/16/19 5:15 pm

Originally Posted by R Moulding
Would it be possible to machine the cast lug from the tube and fabricate a replacement tube that could be welded on as per factory?
Substituting a replacement tube would be complicated because of the threaded fitting at the top of the slider as well as the mudguard bracket on the side.

Easier than replacing the tube on the slider, but still far from easy, would be to slice the casting off that contains the offending tapered plug, refinish the ID of the slider, then weld the casting back on. Complicating holding it in a lathe chuck is the mudguard bracket, but it could be sliced using a slitting saw in a mill if necessary. However, even once it has been sliced off, the casting would be missing the thickness of the slice plus the portion that projects ~1/4" into the tube that registers it as well as minimizes distortion of the tube during welding. So, a replacement piece first would have to be welded on the casting and machined to register with the tube. This replacement piece also would have to be long enough to replace the length of tubing lost in the machining operation, but not project so far into the tube as to interfere with the stanchion at the limit of its travel.

The above leaves the problem of the remaining portion of the original casting that's in the ID of the tube. If the slider minus the end casting can be chucked in a lathe that material could be removed but, if not, ...

All of this would be solved with a hone having an internal ID of 5/8", which is the approach I'm following at this point.
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 01/16/19 7:11 pm

Hi MM,
please forgive my ignorance if this plan sounds implausable, but perhaps an alternative approach is as follows:-
- mount the slider in a lathe with sufficient capacity to hold the tube near the mudguard lugs
- use a drill or tool slightly larger than the tapered plug diameter to bore a hole through the axle hole into the tapered plug. Once bored throgh the slider sufficiently, the tapered plug should fall out
- you should then be in a position to hone the slider internals as required
- next you would have to fabricate a new tapered plug and install it. Perhaps as part of this you could machine a step in the previously drilled slider hole so that the new tapered plug fits with a corresponding step/flange.
- finally you would need to weld/braze everything together again and close the hole previously drilled in the axle mount

Not any easy procedure but food for thought.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/16/19 9:32 pm

Originally Posted by gunner
perhaps an alternative approach is as follows:-...
Yours a very good suggestion that's certainly worth investigating further. Thanks.

As the top of the first photograph shows, other (earlier?) sliders had a through hole for a bolt that held some equivalent to this tapered pin, although that hole is only 0.45"-dia. rather than the 0.63" that would be necessary to remove the pin in Gold Star forks. Still, as also shown at the bottom of this photograph, a 5/8" hole doesn't seem unreasonable.

As for mounting in the lathe, it is easier than I thought it would be. Although the OD of a slider is too large to fit in the bore of my lathe, the second photograph shows that it can be held quite easily. The steady rest can be used to provide stability at the far end.

It's not obvious that such a hole would need to be filled in after making it, although doing so would preserve the original look. Also, rather than making a new tapered pin, the old one could be repurposed by grafting on a section at the bottom with an OD for a press fit into the hole that was made to remove it. A long drift with a 2â…›"-deep hole in it would ensure the pin was installed to the correct height and, if the pin was made a little longer than necessary, trimming the excess that projected into the hole for the axle would leave the slider looking the same as original.

The third photograph is another view of the other (earlier?) slider.

Again, thanks for this suggestion.


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Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/17/19 3:18 pm

The first photograph shows the 1.5" Sunnen mandrel in place in the slider. To use a double negative, it's not completely clear from this that the mandrel couldn't be modified with a hole in the center to allow it to reach the end of the slider.

The second photograph shows a 5/8"-dia. circle on the end of the mandrel, with the same double negative applying. However, the devil is in the detail of precisely where the center of that circle sits.

The top of the third photograph is a top view of the mandrel with a spare stone laying on its side. In red shows the approximate portion of the stone's Al mount that would have to be removed to clear the pin in the slider if a 5/8" hole were bored in the mandrel. The concern is whether enough material would be left on the front nub of the mount once sufficient material was removed from it to clear the 5/8"-dia pin in the slider. The nub fits in the ramp of the wedge to force the stone up or down.

The bottom of the third photograph is a bottom view of the mandrel. In red shows the approximate portion of the shoe that would have to be removed. It's actually the inside face of the shoe that would be removed, but doing so also would remove two of the three tapped holes in the mandrel for mounting it, leaving only one screw to secure the shoe. However, the shoes are a snug fit to the support structure on the mandrel, and they are only are subjected to a sideways force, so it's not clear to me all three screws are needed. But, maybe they are(?).

The biggest uncertainty when considering such a potential modification is the wedge in the fourth photograph. The concern is whether enough material would be left on the bottom ramp of the wedge to supply the necessary force to the remaining nub on the stone's Al mount once sufficient material was removed from the wedge to clear the 5/8"-dia. pin in the slider. Unfortunately, the geometry of all the pieces is complex enough that measurements alone are problematic. It needs to be cut and try.

So, what to do? Risk ruining a mandrel by modifying it, or give up on this idea? If it worked it would be a lot easier to make a one-time modification of a mandrel than to individually machine each fork leg.


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Posted By: George Kaplan

Re: 1957 BSA Spitfire Scrambler - 01/17/19 7:46 pm

Originally Posted by Magnetoman
So, what to do? Risk ruining a mandrel by modifying it, or give up on this idea? If it worked it would be a lot easier to make a one-time modification of a mandrel than to individually machine each fork leg.


Only you can decide on what you want to do.

However.

If it were me and I had one fork to do then I would be tempted to machine the bottom off one fork. However if I had more to do or more that I were likely to do then I would not hesitate to modify a mandrel. And if I ruined one mandrel I would probably buy another and refine my modification.

John
Posted By: gavin eisler

Re: 1957 BSA Spitfire Scrambler - 01/18/19 12:10 am

If it was me I would leave the mandrel alone, you want max rigidity at the cutting face , I like Gunners plan. Maybe use some soft copper between the chuck jaws and the job too.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 01/18/19 11:54 am

The compression bump stop cone is pressed into the bottom of the slider leg, you can remove it by drilling in from the bottom of the leg with a 5/16" drill.

[Linked Image]

If you use a stepped drill you can reattach the cone using a allen bolt up from below but you need to add a slot to the cone and then use the later damper valve drain screws with the extended nose, The nose engages with the slot so the cone does not revolve allowing the allen to be tightened.

Bottom end of cone with drilled hole.

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Inside of leg showing where the cone sat before removal

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Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/18/19 3:08 pm

Originally Posted by George Kaplan
if I had more to do or more that I were likely to do then I would not hesitate to modify a mandrel. And if I ruined one mandrel I would probably buy another and refine my modification.
Originally Posted by gavin eisler
If it was me I would leave the mandrel alone,
One vote for, one vote against.

I have no idea how many forks I'll rebuild in the years to come, but having a tool to do a job correctly, rather than a pursuing a work-around, is how I like to do things. So, the day before my previous post rhetorically asking "what to do?" I already had found a used 1.5" mandrel on eBay and bought it. Ebay's tracking shows it's en route with an estimated delivery date of tomorrow.

Meanwhile, the plot has thickened.
Originally Posted by kommando
The compression bump stop cone is pressed into the bottom of the slider leg,
The first photograph is from the Gold Star Owner's Handbook, showing what looks suspiciously like a pin that is a press fit, as kommando says. I looked again under the microscope and I couldn't tell for sure one way or the other so I machined some more to try to expose the pin. It's steel against steel so I haven't yet seen an interface, and since both are made of the same material I can't etch it to expose the interface (I know, because tried anyway), consistent with it not being pressed in. But, I very clearly see a 1/8"-dia. pin, parallel with the axle that pins the 5/8" tapered pin in place, very much consistent with it being pressed in. This opens up another way of attacking the problem, with a flanking maneuver side rather than from the bottom.

As you might be able to tell from the second photograph, the ends of that 1/8" pin would be in the weld so can't be seen. However, it shouldn't take much grinding or milling to expose both ends on a good set of forks so it could be knocked out. Once it's out an extractor should be able to pull the 5/8" tapered pin out. When done honing the slider the undamaged tapered pin could be reinstalled, a 1/8" pin reinserted, and a minor amount of welding done to restore the original look. The third photograph shows the end of the 1/8" pin more clearly.

I'll be exploring this further over the next few days. Once I remove the 1/8" pin from this already-suffering slider, even if the 5/8" tapered pin is a press fit I should be able to rotate it. All it would take would be a trivial amount of movement to expose the press-fit part of the pin in order to confirm its existence and measure its diameter. I already have the materials in hand to make an extractor tool.


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Posted By: franko

Re: 1957 BSA Spitfire Scrambler - 01/18/19 3:39 pm

" It's steel against steel so I haven't yet seen an interface, and since both are made of the same material I can't etch it to expose the interface (I know, because tried anyway), consistent with it not being pressed in."
With the use of a ACT/OXY torch, play the flame in the area you think the interface is. The edge of the parts will turn blue and the line will show up.
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 01/18/19 4:02 pm

Seems strange that you can see evidence of the pin but nothing of the tapered plug press fit interface. Perhaps the pin had an alternative purpose such as holding the lower and upper fork tube together before welding?

Will be interesting to see what happens when disassembly starts.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 01/18/19 4:12 pm

On the 4 cones I have removed none show evidence of a horizontal 1/8" pin going through them, the pin looks to be just lower than the bottom of the small diameter section pressed into the fork bottom. Of the four 7" Single Sided brake legs I have done this operation on, 2 were B31 legs of Gold Star vintage and 2 were B40 legs of 62 to 65 vintage. I will try and find one of the cones but only found the photo, not an actual cone. Off to the workshop to carry on looking for a cone.

When I was drilling in from below I only went in as far as needed for an allen head to clear the axle, the cones were loose in the legs as I took the legs out of the lathe, I did not need to force them in, the removal of the metal in the drilled hole and the force applied by the drilling operation was enough to release the cone from the grip of the leg. You can see the rust on the level surface that was closest to the top of the bottom insert showing it was not in direct contact with the insert.

Legs for the 8" single sided brake could be different of course, the 2 lugs for the top mudguard stay and the brakeplate torque arm are more substantial.

Found a pic of the B31 cones after removal, these look to be longer on the pressed in section.

[Linked Image]
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/19/19 2:18 pm

It is 0.750" from the center of the axle to the center of the 1/8" pin. After determining that, I flipped the slider over and used a 1/4"-dia. end mill to remove enough material that it "should" have revealed the other end of the pin, but without success. This is shown in the first photograph. Realizing that it wouldn't have been necessary to use a pin running through the entire diameter of the slider in order to stake the tapered pin, I turned the slider back over and started milling into the slider centered on the 1/8" pin.

At some point the sound of the end mill changed so I withdrew the mill and found the remaining portion of the pin was loose enough in the hole that I could pick it out, as shown in the second photograph The depth of the hole measured from the OD of the 5/8" (0.625") tapered pin was 0.54" so it doesn't go all the way through.

Originally Posted by kommando
On the 4 cones I have removed none show evidence of a horizontal 1/8" pin going through them, the pin looks to be just lower than the bottom of the small diameter section pressed into the fork bottom.
Very interesting information. Thanks for posting it. To minimize parallax error, in the third photograph I have the lens centered over the bottom of the cavity in the slider. As can be seen the edge of the hole for the 1/8" dia. pin is just below the bottom of the cavity. I wonder if this means we might be dealing with more than one way BSA used to retain the tapered pin.

With the 1/8" pin out I tried to move the tapered pin, eventually with a Vise Grip clamped as tight as I could make it, but the pin wouldn't budge. As an aside, the red line in this photograph is at approximately the end of the slider tube so the pin wasn't involved in pinning the two pieces together for welding.

Next, I'm going to turn my attention from trying to find ways of removing (and replacing) the tapered pin, to trying to find ways to modify a Sunnen mandrel to work with the pin still in place. Tracking shows the sacrificial 1.5" mandrel arrived in town early this morning and is due to be delivered this afternoon.


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Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/20/19 3:28 pm

For the next couple of days I'll be modifying a 1.5" Sunnen mandrel in a way that I hope will work, but that may turn into a disaster. Don't try this without adult supervision.

As shown in the first photograph, it's no problem to center the round end of the mandrel in the chuck to ~0.0001". Unfortunately, the problem is I need to drill the uneven opposite end that's 10" away from the chuck. I can't use a tailstock center for support because I need to drill exactly where the center would be. But, doing a machining operation on something hanging that far out from the chuck would to lead to tears. Further, the mandrel is self-centering in whatever hole it is used to hone so even if I could determine the geometric center of the uneven end, the center of that rotation isn't necessarily the geometric center. So, what to do?

Assume for simplicity of typing that the ID of a slider is exactly 1.5", although I'll mention what I do to take account of the exact dimensions. I need a support at the far end of the mandrel, and I need a faux 1.5" bore to force the hone to self-center. One piece of 2" OD x 1.5" ID Al tubing can serve both purposes.

As the second photograph indicates, if I center a piece of off-the-shelf Al tube to better than 00005" near the chuck jaws, it has a TIR of ~0.0015" a few inches away. This seems to be the production tolerance of the tube. I could skim the OD to eliminate this TIR but I don't think it will be necessary for my purposes.

As the third photograph indicates, the ID of the tube is concentric with the OD to ~0.006" TIR (in the previous photograph I set the indicator to show the total deviation but in this one it shows the swing on one side of zero -- sorry for the inconsistency). Again, I could skim the OD and re-center on it, then skim the ID based on the now-skimmed OD, but I don't think that will be necessary. However, I might change my mind before machining the mandrel.

I then tapped two 12-24 holes in the Al tube and the fourth and fifth photographs show how this piece functions. Pressing the shoes of the mandrel against the ID of the tube with the 12-24 screws "self-centers" the mandrel in the same way it will be done by the honing stones in operation. Here, shims between the Al tube and the shoes will take care of the difference in actual IDs of the Al tube and the slider. This places the rotational center of the mandrel when adjusted for a 1.5" hole directly in line with the tailstock of the lathe. As an aside, your eyes aren't deceiving you. The slot for the stones isn't perpendicular to the mandrel.

The fingers on the steady rest are adjusted to give minimum runout on the OD of the tube, which in turn gives minimum runout on the ID (within manufacturing tolerances). The tube then both supports the mandrel as well as ensures its rotational center is where it needs to be for the measured ID of the slider. Note that this particular mandrel operates over the range 1.480"-1.625", so the rotational center moves by half this difference, i.e. 0.073" depending on where in the range it is operating. In my case I am modifying the mandrel to operate only for the specific ID of a BSA fork slider so this setup will (or should...) let me drill a hole in the end of the mandrel at the rotational center appropriate for that diameter.

Assuming there are no issues drilling/cutting the mandrel for the 5/8" tapered plug (plus whatever clearance I decide it needs to have), it remains to be seen if the resulting hole is too close to the "top" of the mandrel to allow a stone to operate. My preliminary measurements with the1.5" mandrel I already have seem to show I might be OK. At least, they give me the (over)confidence to proceed.

The sacrificial 1.5" mandrel was delivered by the post office yesterday just as my granddaughters were delivered by my daughter for an overnight stay so work is on a temporary hold.


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Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 01/20/19 6:28 pm

Very interesting MM, great to see work with such precision an detail.

To my untrained eye perhaps one option might be to use the tapered plug to help centre the mandrel. The tapered plug appears to have a straight section near the base, so if you could determine the exact OD of this area you could drill a corresponding hole in the mandrel of equal diameter. When the mandrel is bottomed in the fork tube the tapered plug should then fit exactly inside the mandrel ensuring its concentric. This assumes the tapered plug is concentric to start with and that all the other sliders have the same diameter tapered plug.

Anyway just my ramblings on a Sunday evening after taking my 8 year old daughter to various birthday parties & activities.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/21/19 8:46 pm

Originally Posted by gunner
great to see work with such precision an detail.
If worse comes to worse, I'll have turned the mandrel into precision junk.

Originally Posted by gunner
if you could determine the exact OD of this area you could drill a corresponding hole in the mandrel of equal diameter.
That's the essence of my plan, and it's the reason I'm going to so much trouble to get the offset of the end of the mandrel correct. I need to make the hole as small as possible in the hopes that doesn't screw up the ramp mechanism for adjusting the stones, but large enough to accommodate variations in OD and location of the tapered pins.

As the first photograph shows, after thinking about it I couldn't accept the production runout/concentricity of the stock tube so I skimmed a few thou. off the OD where it will be held by the fingers of the steady rest, then skimmed the ID. This resulted in two surfaces concentric to better than 0.0001", with the final ID 1.519". That's the good news. The bad news comes later.

I then measured the bores of eight sliders. After initial tests of several of the sliders I set the bore gauge zero to 1.4750" and recorded the wear with respect to that figure. I'd ask for bets on where people think the wear would be maximum, but I won't keep you in suspense. The second image shows the results. I measured the diameter with respect to 1.4750" every 2" starting at the top of each slider. The bore gauge hit the top of the pin at 6Âľ", and the bottom of the tube at 8Âľ" in the one slider where the pin had been removed.

Aside from proving I own a lot of colored pencils, all but one of the sliders start between +0.002" and +0.004" (with respect to 1.4750') with one slider showing a constant +0.003" the entire depth. I think there are enough data here to conclude that BSA aimed for a diameter of 1.478". I infer from the values on the graph near the top of the sliders, where the upper bush protected the bore, that BSA's production tolerance was ~+/-0.001". Two sliders (red and orange curves) have wear values significantly greater than the starting diameter at greatest depth, implying most wear for these two was when the forks were almost fully compressed.

Knowing the radius of the sliders, 1.478"/2=0.7390", and of the Al tube that I made, 1.519"/2=0.7595", tells me I need a shim under the shoes of thickness 0.0205" to center a hole in the mandrel in the center of the slider. Two 0.010" pieces of brass shim stock take care of this, as shown in the third photograph.

Another bit of good news is I tested the hardness of the mandrel and it's only RocC 20-25. The mount for the shoes is the same. Had it been hardened the job of drilling it would have been a lot more difficult. I decided to make an Al piece to fill the gap in the mandrel where the stones go to minimize the tendency of the cutting tool to wander, which can be seen in the fourth photograph. This piece has two holes in it for bolting to the mandrel and two holes for the 8-32 screws to pass through to bolt the Al cylinder directly to the mandrel.

Now we come to the bad news part of today's story. I incorrectly thought that the wall thickness of the Al tube would be sufficient to avoid distortion, but the 0.007" runout shown in the fourth photograph is a maximum where the screws that hold it in place (snug, but not too tight) indicate it wasn't. I'll have to make another such cylinder from steel.

What I also need to do is to fabricate a 'go/no-go' gauge of sorts, of OD 1.473" (i.e. to fit down all but one of the sliders), and with initial ID 0.625" (5/8"). If that doesn't fit over all of the tapered pins I'll slowly enlarge the hole it until it does fit. The two reasons for not fitting would be that a pin might be slightly larger than 5/8", or that it might be offset from the center line. Either way, the hole in the hone has to be large enough to accommodate the largest such variation it will ever encounter, and I hope the eight sliders I have are enough to provide representative data.


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Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 01/21/19 10:24 pm

I have one fork leg with an issue that you may want to consider, if I leave the top bush out but put a bottom bush on the station it slides evenly all the way to the bottom. Add the top bush and the stanchion binds 2/3 to 3/4 of the way down . This is a 7" leg and the binding is very close to the brake plate lug so I assume the leg is bent from heat distortion. So a measure of straightness may be useful.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/22/19 6:57 pm

Originally Posted by kommando
So a measure of straightness may be useful.
Great, something else to do. Sigh...

The more I work on this tar baby the more I find there is more to do. As for straightness, I have several electronic indicator gauges so I'll see if the sending units are small enough to reach past the tapered pin. If so, I could mount a slider in the lathe and the head at the end of a long rod and then drag the stylus the length of the slider. Again, sigh...

However, finally, something good thing has come from all of the work on sliders I've done so far. I've repeatedly searched for a tap wrench that went missing months ago. This particular tap wrench is very useful in the lathe because it is long enough to give good leverage, but just short enough to clear the ways so it can be turned through the full 360°. My longer one just won't do so I finally broke down and bought a cheap Chinese substitute that works but is shorter than my missing one so is harder to use. Anyway, in making a go/nogo gauge for the sliders yesterday I picked a length of rod from the scrap box for the handle and decided to use a 7/16"-14 thread on it and the gauge. It's obvious I don't use 7/16" taps very often, as evidenced by the fact I found the missing tap wrench in the 7/16" tap drawer(!). Note: in case anyone is wondering about the contents of that drawer, I have separate drawers for 4-40 up through 1/2"-13 holding the appropriate drill bits along with the taps, making it quick to grab what I need rather having to consult tables and track down taps in one place and drill bits in another. The smaller drawers have a divider for separating coarse and fine in each size, but starting with 7/16" the drill bits are too long to use a divider which is why in the first photograph you see them mixed together. It's also why the tap wrench fit in that drawer, whereas it wouldn't have in one with a divider.

For the go/nogo gauge I started with 1.4750" but after several test fittings I ended up making it with a 1.4710" OD. As an aside, a close-fitting gauge does a great job compressing the air in the slider. As the second photograph shows, I reamed it 5/8" (0.6250") knowing that if that ended up being too tight a 16 mm reamer (0.6299") would precisely enlarge it by 0.005". As shown in the third photograph, with the go/nogo gauge in this configuration it went the full length of five of the eight sliders (although, one is of the old style with the tapered pin having been removed). In retrospect, I suppose it shouldn't be too surprising that a pin in a part made on a lathe would be accurately located in the center of the part.

With three of the sliders the gauge stopped ~1.5" from the bottom. This could have been because the pin was fatter than 5/8", was offset in the bottom, or the ID of the tube was less than 1.471". After enlarging the hole in the gauge in increments without success, I then reduced the OD of the bottom 1.5" of the 2"-long gauge. When I got to 1.462" it went all the way into one of the three, and at 1.640" it went into the second one, and finally at 1.458" it went into all three.

What this means is in modifying the Sunnen mandrel I have to assume the ID of some tubes could be as much as 0.020" smaller than the 1.478" measured at the top. However, before I can declare final victory I have to make another gauge that is 1.458" OD at its lower 1.5", 1.471" above that, and with a 5/8" hole reamed in the center because the hole in this first gauge is now larger than 5/8".


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Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 01/22/19 7:36 pm

Looking at the fork slider wear graph previously posted there seems to be a fair amount of variation between wear at the top and bottom. Given the arrangement of the bushes I would have thought that all sliders would be more worn at the bottom since the lower bush slides against the fork slider whilst the upper bush slides against the stanchion. However I guess there may be other variables involved such as how often the fork oil was changed and how the bike was ridden.

This is all leading me to a question of what size will you ultimatley hone the sliders to? Will you choose the slider with the most wear and hone all the sliders using this size to an ID sufficiently large to remove the wear and make all the sliders have the same internal diameter?

This then leads on to replacement bushes for the forks, I'm assuming you will be making new bushes to exactly fit the newly honed sliders, but will you tailor each bushing for its slider or work to a standardised sized based on a standardised hone ID?

Anyway keep up the good work, it helps give some cheer to an otherwise dark and gloomy January smile
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/23/19 2:18 pm

Originally Posted by gunner
This then leads on to replacement bushes for the forks, I'm assuming you will be making new bushes to exactly fit the newly honed sliders, but will you tailor each bushing for its slider or work to a standardised sized based on a standardised hone ID?
Before modifying the mandrel I plan to take one of the old-style sliders with removable tapered pin, measure its bore vs. depth every 1", and then hone it to see how uniform I can make it, and how much material I have to remove to do so.

One could imagine working on a bike with one slider worn like the red curve in a previous post (+0.010") and the other like the purple (-0.001"). I would have to decide whether to try to make them both the same for standardization reasons, in which case a lot of material would have to be removed from the purple slider, or whether to independently make each as uniform as it could be made and then make bushes for each slider that were appropriate for it.

As for making the replacement bushes, first I'll have to figure out how much clearance is ideal, i.e. somewhere between sloppy and seizure.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 01/23/19 6:15 pm

Modern practice is to use PTFE lined bushes, the bush base is steel with a bronze powder sintered onto one surface in a mono-layer ie one powder particle thick. A PTFE mush is rolled over the sintered side and heated to bond to the sintered bronze. All this takes place on flat strip, after the material is made it is then cut to width and length before being formed into circular bushes with the PTFE on the inside or the outside depending on its use as a lower or upper bush.

[Linked Image]

The US maker of these bushes was Garlock but they look to have dropped out. Competition from China is fierce.

There are standard ranges in both metric and imperial sizes like there is in ball bearings, so if you can get one to fit they will be cost effective, bespoke sizes would be too expensive.

I would combine them with the new SKF low friction dedicated fork seals for the lowest stiction possible, one of the Mountain bike suspension seals may be small enough.



Posted By: koan58

Re: 1957 BSA Spitfire Scrambler - 01/23/19 8:04 pm

Over the decades of use, it would be surprising if at least some of the sliders haven't suffered front end impacts, which may result in minor distortion only evident with the precision measurement that you are conducting.

Kommando's post suggests this possibility, it is more likely for the injury to happen to the lower part of the slider (forks compressed).

Maximum front braking force also happens in this situation, which may lead to more wear in this area of the brakeplate slider. The other slider only experiences whatever the rigidity of the wheel spindle assembly transmits.

It's not clear from the colour pencils coding which side the sliders are. If they were paired for contrast it may be revealing.

When you measured the bores of the sliders, did you compare fore/aft to sideways? Ovality would not be surprising.

I wouldn't have the equipment or skill to do such a thing, but I do think establishing straightness of the slider bores would be important.

You could of course rebore a warped slider to a straight bore, centred on the taper pin and upper bush. The geometry should still be original, only the outside would be a few thou askew.

I am confident that you will find an interesting quality solution!
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/24/19 4:21 pm

Originally Posted by kommando
Modern practice is to use PTFE lined bushes,...
Thanks very much for that information. I'll be restoring the Spitfire's forks as-original, but everything is on the table for bikes other than it.

Originally Posted by koan58
When you measured the bores of the sliders, did you compare fore/aft to sideways?
The 5 images/post limitation means I often have to leave data out of a given post.

In its present configuration my BSA slider plug gauge has a stepped OD, with it 1.458" on the lower 1Âľ" and 1.466" on the ÂĽ" above that. With the ID reamed 5/8" (0.6250") the gauge went all the way to the bottom of 3 of 6 sliders. With the ID enlarged by ~0.005" with a 16 mm reamer (0.6299") the gauge went all the way to the bottom of 5 of the 6, and gentle tapping drove it to the bottom of the 6th. As the first photograph shows, machinist's bluing on the gauge showed just one side of the pin rubbed on the inside of the gauge so this pin is offset from the center by ~0.003" rather than oversize. The values from this go/nogo gauge will inform the modification needed to the Sunnen mandrel to allow it to reach the bottom of the sliders. Careful measurements will determine if this can be done while still leaving enough remaining of the wedge to operate stones.

As a test of how well honing works I picked one of the "old style" sliders that already had the tapered plug unbolted and removed from it. I found a 10-32 nylon screw threaded into the drain hole without problem so I cut the head off, drilled it with a ~0.07"-dia. bit, and used it to supply honing oil to one end of the slider. A short length of Tygon tubing connected the screw to the Sunnen's oil supply, as shown in the second photograph. I also used three stoppers to plug the holes in the end of the slider. Despite the small size of the hole in the screw it flowed nearly as much oil as the unrestricted line.

Before starting to hone I measured the bore parallel and perpendicular to the axis of the axle every 1" along the length, as shown in the red curves in the third photograph. As can be seen it was somewhat oval with a maximum difference between the two directions of 0.007".

Using a formula in the Sunnen catalog I calculated that it should take 31 sec. to remove 0.002" from the inside of a uniform 1.5"-dia. tube using a roughing stone. I stopped after ~30 sec. to make a set of measurements, then again after an additional ~1 min. or so. I only plotted the latter measurements on the graph. As can be seen, the honing preferentially "attacked" the locations where the bore was smaller, reducing the "ovalness" by over a factor of 2. A very rough visual average of the amount of material removed is consistent with the Sunnen formula.

The important point is that because of the way the hone preferentially removes material from locations with smaller ID, less than 2 min. with the hone made the ID significantly more cylindrical. And it did so while only increasing the "average ID" by a small amount. I'll spend a few more minutes in the hone with this slider this weekend to see how close I can get it to a perfect cylinder.

I used 150-grit stones for reasonably fast material removal which a Sunnen table says will give a finish of 20 µin. in "hard steel" or 35 µin. in "soft steel". There's no indication of what they consider "hard" and "soft" but I measured the roughness to be 19-22 µin. It appears that this is just about ideal, since smoother surfaces will have more stiction.

I also have made some progress on finding what clearances to use for the bushes in the 'General Data' section of service manuals

__________clearances _ top __________ bottom
'67 BSA B44 _______ 0.0005" ______ 0.002"-0.003"
'65 BSA A65 ____ 0.0005"-0.0015" __ 0.001"-0.004"
'69 BSA A65 ____ 0.0035"-0.005" ___ 0.0035"-0.0065"
'63 Tri 650 ______ 0.0035"-0.005" ___ 0.0035"-0.0065"
'68 Tri 650 ______ 0.0035"-0.005" ___ 0.0035"-0.0065"
'68 Tri 500 ______ 0.0035"-0.005" ___ 0.0035"-0.0065"
Trident _________ 0.0035"-0.005" ___ 0.0035"-0.0065"
'70 Commando ___ 0.0005"-0.003" ___ 0.0005"-0.003"

If anyone has BSA shop manuals from earlier than 1965 I would greatly appreciate it if you would look for the fork bush clearances in the 'General Data' section in the front of the manuals

As a reminder, the top bush works with the OD of the stanchion and the bottom with the ID of the slider. It's easier to accurately make a shaft round than it is a 7"-deep hole so I suspect the larger clearances for the bottom bush reflect production tolerances as much as they do required operating conditions. Given tolerances that can be as small as a half-thou., I have to wonder how much clearance exists with aftermarket bushes. I suspect in 98% of cases the owner/mechanic simply installs them without making any measurements.


Attached picture Mandrel09.jpg
Attached picture Mandrel10.jpg
Attached picture Mandrel11.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/26/19 6:26 pm

Thanks to yeoman work by Shane in Oz in scouring BSA parts books I now know to what extent A7/A10 forks survived unevolved into the Modern Era. For example, 1965 A50/A65 Cyclones and Spitfire Hornets used the same part numbers for the stanchions as 1960-63 A10 Spitfires, and 1962-65 A50/A65s used the same L and R sliders. Shane assembled enough information to be confident that pre-unit fork bushes should use the following clearances that are found in A50/A65 manuals:

Top: 0.0005"-0.0015"
Bottom: 0.001"-0.004"

The last figure in my previous post shows where I stopped after only a few minutes with the hone. In its current condition, if I made a bush with ID 1.4815" it would have a clearance of 0.001" perpendicular to the axle when the slider was 4" below the top and 0.0042" parallel to the axle at 7". Even though this would nearly meet BSA's specifications, today I'll see how much better I can do with a few more minutes of work on the Sunnen.

Although the top clearance is tighter than the bottom it will be easier to achieve since it is determined by the OD of the stanchion rather than the ID at the bottom of a 9"-long tube.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/27/19 5:41 pm

A Sunnen hone is a miracle tool, allowing a self-trained operator to make a 1.5"-dia. hole cylindrical over its entire 9" depth to better than 0.001" without much effort. Part of my self-training was learning from trial and error over the past few days that for this accuracy with long mandrels that take more than one guide shoe it's essential to have a matched set of shoes. This isn't the same as having used guide shoes that look the same and have identical part numbers on them. Obvious in retrospect is the shoes have to be worn by the same amount to have identical thicknesses in order to achieve the highest possible accuracy over the full length.

It still remains to be seen if I can successfully modify a 1.5" mandrel to reach the end of sliders when the tapered plugs are still in place. The major uncertainty is with the wedge, and to give me the greatest chance of success with it I have on order a new set of guide shoes. They will lower the center of rotation of the mandrel slightly and thus it will require removal of the least amount of material from the bottom of the wedge. Every thou. counts.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/29/19 3:40 am

A week ago the friend who gave me my DocZ rollers asked if he could borrow them to get a Ducati running. Of course, I agreed. However, the high compression pistons in that bike, coupled with his need to run the rollers for more than a few seconds, revealed weaknesses in the present electrical system of the rollers. So, I brought the DocZ home and today I ran new wires and a heavy ground strap and it's now ready for a 200 Amp relay that I'll connect in parallel with the present one. The relay is due to be delivered tomorrow.

Although I'll use the rollers on the Spitfire someday, the more directly related work was disassembling a set of very rusty forks to use for additional measurements and experiments. I had used Kroil on them a week ago and with a mallet managed to get one leg to move. Today I got the other one to move by using the 30T hydraulic press.

Although I have the correct tool for removing seal holders, the springs on both sides were solidly held by them so I couldn't use the tool. But, what's the point in owning a huge pipe wrench if you don't use it once in a while? The first photograph shows how you should never (except under exceptionally rusty circumstances) remove seal holders.

The second photograph shows how rusty the stanchion is. Once I managed to pry the circlip out of the rust it still took a big hammer to remove the slider from the stanchion.


Attached picture Forks_rusted01.jpg
Attached picture Forks_rusted02.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 01/31/19 7:18 pm

Originally Posted by Magnetoman
I brought the DocZ home and today I ran new wires and a heavy ground strap and it's now ready for a 200 Amp relay that I'll connect in parallel with the present one.
The DocZ has been upgraded and is now back at my friend's shop. I didn't think to check when under load, but when not under load each motor draws ~130 A, which is 4 hp for the pair.[*] This is why a big battery with a high CCA rating is needed. An annoying problem with the DocZ since the beginning is the battery clamps. I keep intending to modify them to give a greater contact area with the terminals so they can handle the 300+ A under load without excess voltage drop.

[*] Under load they each draw 240 A, which is 7.7 h.p. of leg-saving, motorcycle-starting power for the pair.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/03/19 6:09 pm

Thanks to a post in another thread I discovered I had overlooked a BSA Parts Service Bulletin with information applicable to my Spitfire. I scanned that Bulletin and added it to an appropriate page early in this thread. Unfortunately, this means I'll now have to carefully go through all those Bulletins, BSA Service Sheets, and Hap Alzina literature to see if I overlooked anything else.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/05/19 3:39 am

To finish with the DocZ saga, I modified the existing battery clamps by adding segments of 1" ID Cu pipe to have much more surface area in contact with the 1" OD brass terminals I attached to the battery. They work great.

To complete the rusty stanchion saga, none of my BSF/BSW sockets fit the cap at the bottom end of the stanchion so I measured the distance across the flats to be 1.203", making it an 11/16 BSW. However, my socket of that size was significantly too large. However, I have a deep-drive 1-3/16" (1.188") A/F that substitutes for a proper 11/16" W socket that was a snug fit on the cap. It then took the 200+ ft.lbs. of my battery-powered impact wrench for nearly 5 sec. before the cap moved. But, after that it spun off without problem.

I then took time off from the Spitfire to change the oil and filter on one of my Ducatis and then perform a shell game to reposition the bikes, leaving my Competition Gold Star on the lift. I need to disassemble the forks to replace the clip-ons with a set of flat bars I have to give the rider a more upright position. I'm planning for the Three-Gold-Star ride I'm organizing for later this Spring to spend a fair number of miles on dirt roads in the mountains and clip-ons are far from idea for that. Also, planning for the future -- the far, far future, I hope -- with bars in the "normal" mounting position it will be a relatively easy job to switch to ever-higher bars as dictated by creeping decrepitude.

I still need to finish modifying the Sunnen mandrel to reach past the tapered plug at the bottom of the slider but that will require a piece of steel pipe that I haven't started looking for yet. I discovered the thick-wall Al tubing I assumed would work distorted too much in the lateh.


Attached picture Forks_rusted03.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/06/19 3:40 am

I needed to hone a slider to wear in the stones so I could make accurate measurements of what needed to be removed from the mandrel, stone, and wedge to allow it to reach past the tapered plug. Unfortunately, having done so, the image shows my Plan A won't work. Shown in red are the portions of the stone and wedge that would have to be removed. I do have a more complex Plan B (and C) but it will take some time to explore it in detail to see if it can work. Meanwhile, this moves to the back burner.

Attached picture Mandrel_modification.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/07/19 1:07 am

Originally Posted by Magnetoman
Shane assembled enough information to be confident that pre-unit fork bushes should use the following clearances...:
Top: 0.0005"-0.0015"
Bottom: 0.001"-0.004"
Having recently gained way too much familiarity with the innards of pre-unit forks, I optimistically assumed rebuilding the ones on my Special Competition Gold Star would be simple. So today I took one step forward with them. I'm now at least three steps back although I've only removed and measured one leg so far.

It has been configured as a road racer since I bought it, with large Lyta tank, rear sets and clip-ons. However, as I mentioned in a recent post, I want to replace the clip-ons with bars that will be more appropriate for use on an upcoming ride with my Cannonball partner and another friend who I'll generously say has a 50/50 chance of not having another commitment arise at the last minute. Anyway, at a minimum the fork legs have to come off the bike to remove the clip-ons so I might as well use the opportunity to check the condition of the bushes and install new seals. I'm not sure who was more correct, whoever said "leave well enough alone," or "too much knowledge is a dangerous thing." Sigh...

What matters are the IDs of the top bush and slider, and the ODs of the bottom bush and stanchion. I have a complete set of measurements, but making a long story short, the clearances to be compared with the values given above are:

Top: 0.0055" - 0.0095"
Bottom: 0.0068" - 0.0115"

The range accounts for ovality and differential wear on the parts. But, hey, other than the clearances being ~5x too large, what could be a problem? Sigh...

The bottom of the stanchion is protected by the bottom bush so it should have the original OD. I did not keep track of the orientation of this stanchion when I removed it, but the ODs measured 90° apart are both 1.2480". This means that, assuming the top bushes were reamed to size by the factory (i.e. 1.2500"), the original clearance would have been 0.0020". The same measurement made 5" above the bottom of the stanchion found 0.001" wear in one orientation and 0.0002" in the other.

I don't have the same OCD desire to rebuild this bike to 100.0% originality as I do the Spitfire, but neither do I relish going down the rabbit hole of aftermarket parts with stanchions and bushes. I just want to get the forks properly rebuilt and the bike set aside to wait for spring so I can turn to other projects. What to do? What to do?
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 02/07/19 12:38 pm

Not much wrong there and the potential to make it worse not better with new parts made to the book clearances hence the quandrey.

Whatever the reason for the excessive OEM clearance ie ease of assembly or loose fits that allow good fork action, your forks work with the tight clearance you have so why change it.

So to remove risk of new parts and increase the likelyhood of improving what you have is the objective.

My suggestion is.

You can get the current stanchions hard chromed back to size and if you pick the right supplier then ovality and straightness should be as good or better. You also gain better conditions for the seal and the top bush, eg lower stiction and higher surface finish than original. Cost will be higher than off the shelf but pick the right supplier and its worth it.

New seals, but the bushes may not need changing, the top bushes set the size of the rechomed stanchion so unless out of round size the stanchion to these, lower bush more likely to need to be custom if you use the Sunnen on the fork lower.
Posted By: GrandPaul

Re: 1957 BSA Spitfire Scrambler - 02/07/19 2:17 pm

Yep, love my DocZ kit. It has kept me from having a much larger right thigh than the left one... (also from hyper-extended or compression-injured right knee)
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/07/19 5:44 pm

Originally Posted by GrandPaul
Yep, love my DocZ kit.
I finally took the time to properly deal with the inadequate battery clamps mine was equipped with. I now have a pair of 500 A welding clamps on it that provide relatively large areas of Cu, rather than just the contact made by a few sharp teeth, to conduct the ~250 A from the battery terminals that the two motors draw under load.

Originally Posted by kommando
My suggestion is.
You can get the current stanchions hard chromed back to size...
...lower bush more likely to need to be custom if you use the Sunnen on the fork lower.
Thanks very much for your suggestions. I sent a request for quote to one hard chrome company whose web page makes it seem they might deal with small quantities of small parts (compared with massive rollers) and am waiting to hear back from them. Meanwhile, in the interests of exploring all options, I also sent a request to the well-known (in the U.S.) Franks Forks, but they replied they don't make those stanchions. Aftermarket stanchions from a dealer do remain an option (assuming the dealer has a tenth-reading micrometer).

Aside from hard chrome or actual replacements, I assume the asymmetric wear I found in the middle occurred primarily in the fore-aft direction. So, if I indexed the stanchion in its current condition when installing it to make the wear direction side-to-side the important fore-aft clearance would vary by a negligible 0.0002" over the entire length. So, as kommando said, it's not as bad as the present clearances indicate at first sight, and nothing that couldn't be corrected to almost as-new condition with a pair of bespoke bushes.

If the second slider turns out to be the same as the first I'll be inclined to leave the Sunnen on the shelf, so to speak. The ovality and wear of this first slider is such that if I size the bottom bush to give it the specified min. clearance of 0.001" at the tightest location, the clearance will be less than the max. spec of 0.004" at the widest location. Further, that wide clearance happens when it's near full compression, and over most of the travel the clearance would be less than 0.0025". Again, though, I may have to reconsider once I take the second leg off and examine it.

Posted By: gavin eisler

Re: 1957 BSA Spitfire Scrambler - 02/08/19 6:34 pm

Turning stanchions 90 degrees to change the wear spots never worked for me, fork legs take a set / slight bend usually around the bottom yoke area, if you turn them they stop being parallel . How straight are your stanchions?
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/08/19 10:13 pm

Originally Posted by gavin eisler
How straight are your stanchions?
I beg your pardon, sir... oh, the fork tubes on my motorcycle. I haven't measured that yet but will tomorrow, along with the straightness of the slider. Today I was abducted for a forced march up a rocky trail through a canyon into the mountains so work on the forks was on pause.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/10/19 12:30 am

Originally Posted by gavin eisler
How straight are your stanchions?
The answer is, it depends. If you want to know how straight the bottom ~9" is that fits in the slider, it's straight to better than 0.001". The rest, not so much. If I clamp the straight section in the lathe the TIR at the top is 0.28", i.e. it has been bent by ~1/8". However, I spent much of the afternoon making and refining a jig to clamp the straight section so it can't be distorted and removing the bend in the rest. Going back and forth between the 30T press and the lathe I got the TIR down to 0.030" before I had to call it a day. Tomorrow I'll remove the remaining 0.030"/2=0.015" bend and upload a photo of the jig that I fabricated after I finish the refinements (I ignored the small pointer when I arbitrarily adjusted the large pointer to read '0' at the low spot then turned the chuck 180-deg. and the photo displays the 0.030" reading at the high spot)


Attached picture BentStanchion.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/10/19 10:31 pm

I have my stanchion straightening jig in final form, but please be gentle in your criticism of the welds. I repurposed a heavy steel bracket that already had risers with 90-deg. bends welded on both ends, and it stretched my 200 A TIG machine to the limit to weld the 1/2"x2" steel bars to those risers as well as to the length of the steel pipe, although switching to my 50/50 He/Ar bottle definitely helped. The photograph is an "exploded diagram" so the individual pieces of the jig can be seen.

Anyway, the feet at the left end are rigidly clamped to the I beams of the 30T press which serves as the reference surface. The ~9" section of 2-1/8" ID steel pipe is centered in the press allowing pipes of any length to pass through both sides of the press to be unbent. Three 3/8" tapped holes in the steel (not cast iron) pipe are used to clamp a sectioned 1-1/2" ID Al tube against the stanchion to keep that portion straight and unmarred. The largest diameter on my Gold Star forks is 1-3/8", but by using tubing with a slightly larger diameter than that it will be possible to insert tubing that is somewhat bent as well. This is one of the ways I tried to design a jig that was as universal as possible.

It can't be seen but I cut a gentle taper in the end of the Al tube that I further rounded with a half-round file before sectioning it to avoid a sharp surface pressing against the stanchion. It also can't be seen from this photograph but the bottom of the steel tube presses tightly against the steel block under it so it's impossible for the jig itself to bend even slightly when pressure is applied, which would complicate the dial indicator readings if that happened. As (over)built, the jig does not deflect with respect to the surface of the press it's mounted to so 0.001" change in reading of the dial indicator is 0.001" change in bend of the stanchion.

A piece of Al square stock drilled 1-3/8" and then sectioned is what the press presses against, again to avoid marring of the stanchion. Thanks to having 30T at my disposal the press does not need the additional leverage of pushing against the end of the stanchion. This will be very helpful, if not essential, if straightening tubes that are kinked in several places.

The principle of operation for a one-kink bend is I put the straight end in the lathe and measure the TIR at the far end, marking the high point. I then clamp the straight end in my jig and adjust a 1"-travel dial indicator to be '0' close to its maximum travel (because pushing down on the stanchion reduces the reading on the indicator). I then sneak up on the bend by successively pressing ever larger deflections, removing the pressure, checking on the indicator how much the bend has decreased, and repeating until it has decreased by 1/2xTIR. In principle this only should take one attempt, but in practice a few trips back and forth between the press and the lathe are required.

So, this jig gives me yet another specialized BSA tool to put on the shelf and forget I have by the time I need it again...


Attached picture StanchionStraighteningJig.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/12/19 3:14 am

Although I got some other things done today, I didn't get much accomplished on the Spitfire. The only tangible result is shown in the photograph. The taper at the top of the stanchions makes it impossible to grip with the chuck on the Sunnen. So, to mount them I modified a chewed-up top cap by drilling it in the lathe and silver soldering a short 1/2"-dia. stub of stainless rod. It works well.

Attached picture Stanchion_nut_Sunnen.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/13/19 2:23 am

The only two things I accomplished today[*] were to paint the stanchion bending jig with etching primer, and open a box from McMaster-Carr containing the bronze I'll use to make bushes for the forks. A thinner-walled tube of bronze would have been cheaper but the tolerance on the OD was such that it might have been a few thou. too small and didn't want to take the chance.

[*] Many years ago when I lived in Illinois I learned the principle from another motorcyclist that even on days when you don't have time to do anything, it's important to do something. The progress on such days may be minor but it adds up.


Attached picture BronzeTube.jpg
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/14/19 3:43 am

Although the three images in this post are from work on my Competition Gold Star, they're applicable to this Spitfire restoration. I removed the second fork leg today and found something interesting/distressing, as discussed below. Before getting to that, the first photograph shows a socket I made that makes dealing with the weird top nut on the forks easy.

The second photograph shows the nut and washer that are at the bottom of stanchions dropped into my cutaway slider. Interestingly, as can be seen, at full travel the washer will make contact with the ID of the slider rather than the nut with the bottom of the slider.

The third photograph reveals a lot. Instead of the stanchion being smooth the surface has machining marks in it. The OD of the stanchion is correct so it hasn't been re-machined after leaving the factory, and the grooves are circumferential so they're not due to wear. To be accurate, the diameter in the middle region where the grooves are located is worn by ~0.0015". While a smooth region under the bottom bush has a roughness of ~30 µin, these machining marks are a huge ~175 µin. An apprentice machinist must have been in charge the day this one was made.


Attached picture ForkNutSocket.jpg
Attached picture SliderWasher.jpg
Attached picture Stanchion_roughness.jpg
Posted By: George Kaplan

Re: 1957 BSA Spitfire Scrambler - 02/14/19 8:13 am

Originally Posted by Magnetoman
An apprentice machinist must have been in charge the day this one was made.


And Quality Control had the day off!

John
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 02/15/19 5:45 pm

Quote
An apprentice machinist must have been in charge the day this one was made.


Having worked in Birmingham machine shops in the 80's its more likely the auto machine was running unattended and swarf was jammed into the tool-holder and was being dragged across the workpiece as the tool was returning to its start position.

Something like this

[Linked Image]

They were set up by a tool setter and then left to run with a labourer feeding the tubes with steel bar/tube and left running.
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 02/15/19 8:47 pm

Quote
The third photograph reveals a lot. Instead of the stanchion being smooth the surface has machining marks in it.


Would be interesting to see what kind of finish the fork sliders have internally, I wouldnt be suprised if some have a similar machining marks.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/16/19 3:11 am

Originally Posted by kommando
its more likely the auto machine was running unattended and swarf was jammed into the tool-holder
Thanks very much for posting that interesting photograph. So, if an apprentice is at fault it might have been one working in quality control that day.
Originally Posted by George Kaplan
And Quality Control had the day off!

Originally Posted by gunner
Would be interesting to see what kind of finish the fork sliders have internally,
Your wish is my command. The first photograph shows that the probe on my roughness tester isn't long enough to reach more than ~2" into the slider, which isn't past the region that was covered by the top bush. However, because it was protected by the bush this region should have the roughness with which it left the factory. Sighting down the slider with a flashlight doesn't reveal any obvious difference in roughness further down but maybe tomorrow I'll deploy the borescope to see what I can see. Anyway, as can be seen from the second photograph the roughness is ~ 20 µin. which is, ahem, roughly the same as the smooth regions on the stanchions.

With the wheel and stanchions off, and the steering damper fully disengaged, the yokes felt like they were turning in tar. In for a penny, in for a Euro, as the Brits say, so I disassembled the yokes to grease the bearings. The top of the second photograph shows what I found. The race is coated with what looks and feels like roofing tar. Well, that explains why it felt like it was turning in tar. My records of the rebuild ~25 years ago don't mention what grease I used, but what remains of it today is sticky like roofing tar, making it impossible to scrape off. Acetone didn't do a thing to it, but ten minutes in my bucket of Gunk+diesel, plus another minute or two with a brass brush, completely removed it.

I did the same with the tar on the race in the bottom yoke, but the two races in the frame required a little more work because, as indicated by the third photograph, there wasn't any easy way to let them soak in the mixture (I'd already scraped away quite a bit before taking this photograph). I used a paper towel to sort of soak them, alternating with a brass brush and some more of the mixture, and another paper towel to wipe away residue. After less than ten minutes each the races in the frame were as clean as the two that I was able to soak.

The balls are more problematic since there are a lot of them (40 total) and they're too small to easily hold to scrub with a brush. I soaked them in the mixture and wiped as much away as I could, but they're spending the night marinating in a witch's brew of MEK + toluene.

Note: I should mention that the above describes what I found on my Special Competition Gold Star, not my Spitfire. I'm posting the information here rather than in a new thread since the forks are the same.



Attached picture Slider_roughness01.jpg
Attached picture Slider_roughness02.jpg
Attached picture Race_tar01.jpg
Attached picture Race_tar02.jpg
Attached picture Balls_tar.jpg
Posted By: Tridentman

Re: 1957 BSA Spitfire Scrambler - 02/16/19 4:45 am

That color of the grease together with its consistency would indicate to me the use of a grease with molybdenum disulphide in it.
I have seen a similar effect ---a thick tar like appearance from use of that type of grease.
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 02/16/19 12:42 pm

Quote
So, if an apprentice is at fault it might have been one working in quality control that day.


In the 80's quality control was not high on the agenda, BS5750 (now the modern ISO9000) had been published in 79 and was being 'Looked at' during my apprenticeship, I very much doubt in the 60's a quality control bod of any description was checking parts at random and plotting dimension as the dept did not exist. An internal inspection dept maybe, more likely an incoming parts inspector as a favour, Quality Control no, at it would not have existed except in Rolls Royce maybe.

On the ID's of the stanchions OEM are rougher than the current replacements, as I doubt no one bothers with the insides except the threads top and bottom that must be a function of the feedstock not machining by the stanchion maker.


Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/16/19 8:16 pm

Originally Posted by Tridentman
That color of the grease together with its consistency would indicate to me the use of a grease with molybdenum disulphide in it.
The color is grey, not dark brown, so that would make sense. Apparently twenty-five years is long enough for the organic part of the grease to evaporate and/or turn into CO2. As of two years ago my new favorite grease for purposes like this is Mobil 1 Synthetic because it has a drop temperature of 550 °F, which is higher than the minimum of 500 °F that Michael Morse of Vintage Brake recommends for use on wheel bearings of racing bikes.

Originally Posted by kommando
On the ID's of the stanchions OEM are rougher than the current replacements, ...
On the subject of replacement stanchions, not self-tied to the yoke of originality on this Gold Star, and wanting to get this maintenance job finished so I can move on to something else, last Sunday I ordered a set of replacement 40-5027 stanchions from MAP. They arrived yesterday, only five working days after I placed the order. I bought them through eBay because the price with free shipping was ~$10 less than the price on their web site where shipping was extra. In case anyone else is interested in replacing their knackered stanchions, the details I measured on these are given next.

MAP's description says they're for 1950-61 Golden Flashes but includes part number 42-5027 which is what DBD Clubman Gold Stars use. Although their description clearly states they come only with the top bushes, and that the bottom ones must be ordered separately, the photographs show the stanchions with both bushes. Anyway, although I expected to make those bottom bushes myself, they came with both (although, because of wear of my sliders, I'll end up making a set myself no matter what).

The stanchions are beautiful and have ~20 µin. roughness along the length that fits in the sliders. As shown in the first photograph they are 3/4" longer than the ones from my Gold Star. Although the fatter "collar" that is clamped by the lower yoke can't be easily seen on the MAP stanchion in this photograph, it is aligned with the collar on the BSA stanchion when the bottoms of the forks are aligned, which means the extra 3/4" length is above that point.

I was worried this extra length would be an issue, but the second photograph -- this time with the tops of the stanchions aligned -- shows the position of the lower yoke in red, with the collar on the MAP stanchion marked in blue to make it more visible. The collars are 2" high on both stanchions whereas the height of the yoke is only 1", allowing room for misalignment. However, as can be seen from the photograph, only half the BSA collar was clamped by the stanchion whereas full contact is made on the MAP. This is a case where an aftermarket part is better than original.

The other dimensions on the MAP also seem excellent. For example, the 9Âľ" length at the bottom end that operates inside the slider is 1/8" longer on the MAP than on the BSA one and the OD of that end is 0.0007" larger. The actual OD isn't critical as long as the ID of the mating bush matches, but having them the same dimension as standard BSA stanchions is convenient for interchangeability.

The clearance between the IDs of both upper bushes and the ODs of the stanchions is 0.0025"-0.0030", showing good quality control over both items. The clearances of the bottom bushes with the two sliders varies over the ranges 0.0057"-0.0062" and 0.0078"-0.0094" due to wear of the sliders, not variations in the bushes. If I machine bushes sized to the sliders with 0.001" clearance at the tight ends of these ranges the loose ends will be 0.0015" and 0.0026" respectively, both less than the 0.004" max. specification.

What I don't know about these replacements is the Yield strength of the steel used, which determines whether or not they will take on a permanent bend in use like the BSA ones all seem to. I could measure this myself, but it's a destructive test (or, at least, it leaves them with a bend that I'd then have to remove as best as possible) so I'm not going to do that test.

The third photograph shows the "diaper" I fitted over the bottom of the frame to catch any balls that dropped from the top race, shown in the fourth photograph, during assembly, but it wasn't necessary. However, it certainly was when I disassembled the yokes since otherwise a quarter of them would have fallen onto the lift and from there to who knows where. I attached the balls to the race in the bottom yoke with grease in the same way and held a towel under it as I inserted the steering tube into the frame in case any balls were jarred loose, but it wasn't necessary.

As the fourth photograph shows, I used Mobil 1 Synthetic grease. The gap at ~2:00 indicates it might be possible to cram 21 balls into the race but the correct number is 20. Operation now is so nearly friction-free that the bike risks going into a tank slapper just sitting on the lift at 0 mph.


Attached picture BSA_MAP_stanchions01.jpg
Attached picture BSA_MAP_stanchions02.jpg
Attached picture Yoke_installation01.jpg
Attached picture Yoke_installation02.jpg
Posted By: gunner

Re: 1957 BSA Spitfire Scrambler - 02/16/19 10:13 pm

Good to see you have some decent quality replacement stanchions and that the ball races have been refurbished using synthetic grease. Nice idea with the nappy arrangement, I'm forever loosing steering head ball bearings, clutch rollers etc. during rebuilds, so thats a useful tip.

One thing I don't quite understand is how the longer length stanchions will work without increasing the front ride height and compromising the fork spring loading? No doubt you've got this all under control but some further details would be interesting.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/17/19 12:11 am

Originally Posted by gunner
One thing I don't quite understand is how the longer length stanchions will work without increasing the front ride height and compromising the fork spring loading?
The spring loading easily could be taken care of with a pair of 3/4" spacers to return the preload on the springs to their original value, but that still would leave the extra 3/4" length. But, it's not quite so simple, as the attached photograph indicates.

On the left and right are the stanchion from my Special Competition and from MAP, respectively, and in the middle is another stanchion from my horde. I didn't check all of them because the first two I grabbed (with different rust so from different bikes) are the same length as the MAP.

So, why is my stanchion shorter? The answer is, because I didn't read BSA Parts Service Bulletin No. 9 carefully enough. Upon careful reading and cross-checking it turns out BSA calls these "fork shafts," not stanchions, and Bulletin No. 9 says the Special Competition takes 89-5061 which is the "shaft" for the scrambler. So, I learned from this that scrambler stanchions/shafts are 3/4" shorter than those for Clubmans. However, the Special Competition takes the same springs as the Clubman so with these stanchions/shafts I've simply converted the front end to Clubman specs. This means all is fine with both the ride height and spring loading. Clubman forks aren't even inappropriate since the bike came to me with a roadracing Lyta tank and rearset footpegs.

If I had it to do over again I'd order the scrambler stanchions,[*] just because, but these will do just fine. I've made a note of this so if I ever decided to return it to 100% original specifications I could easily do it with a simple change to the forks.

[*] I'd order the scrambler stanchions if I could find them. Where dimensions are given for the ones advertised under part number 89-5061 it says they are 'approximately 22½"', which is the length of the Clubman stanchions. The scramblers are approximately 21¾" (21-13/16" to be more precise).

p.s. the bottle of 20W "V-twin specific" fork oil I ordered arrived today. I bought it because I'm sure it will work twice as good in my Gold Star V-single.

Attached picture 2BSA_MAP_stanchions.jpg
Attached picture Oil.jpg
Posted By: kommando

Re: 1957 BSA Spitfire Scrambler - 02/17/19 3:06 pm

If you are going to the trouble of making a spacer then rather than just do 3/4" make one to give you a static sag of 1/6th of the fork movement with the usual rider seated. The rear static sag is 1/3rd of the shock movement if you have preload adjusters on the shocks, these with the right spring rates (we will just assume BSA got that right) will give a good balance between risks of bottoming and topping out.
Posted By: Magnetoman

Re: 1957 BSA Spitfire Scrambler - 02/17/19 3:47 pm

Originally Posted by kommando
If you are going to the trouble of making a spacer ...
Assuming the spring rates are correct (which I still have yet to measure), the present parts give me stock Clubman forks. To do it right, as you suggest, would