Britbike forum Forums Thread Like Summary - The acceptable quality of mechanical work

Maybe it's not even reasonable to discuss the following on Britbike (or anywhere else, for that matter), since the posts of relatively few people here deal with issues beyond swapping broken items with replacement ones, or sending components to specialists to repair for them. As an indication, out of the ~60k threads, only a dozen (~0.2%) that weren't started by me mention the word 'Sunnen'.

After watching several hours of automotive machining videos on Youtube (typically not all the way through; just until I saw an example of advice that made me cringe) on installing and cutting valve seats, installing valve guides, honing cylinders, etc., I didn't find a single one that didn't have at least one significant error. By that, I mean an error that would have an effect on the function or lifetime. For example, someone deliberately bending the cutter sideways against the pilot to cut a portion of the seat that the cutter hadn't hit (because it wasn't concentric with the guide), making a new seat from relatively soft steel, using an incorrect interference fit for a new seat, determining the "clearance" of the valve in the guide based on how much it rocked back and forth, etc.

Turning to books, most motorcycle "restoration" books basically just describe taking parts off a bike, cleaning or replacing them, and bolting them back on. Unfortunately, even a 250-page book is severely limited in the level of detail possible. Despite the 247-page length of Radco's 'The Vintage Motorcyclists' Workshop', its Chapter 3 "Engine Work: The Top Half" is only 34 pages long. Contrast this with a book from the automobile world, John Edwards' 494-page 'Sunnen's Complete Cylinder Head and Engine Rebuilding Handbook', which covers the same subject matter, but at a depth requiring over fourteen times more pages.

In an offline discussion with Shane in Oz about this I mentioned it was impossible to know if my observation about Youtube means many automotive machinists don't even know proper procedures, or if only "bad" machinists make Youtube videos. Shane responded that I was looking at those videos from the point of view of a precision machinist not a motorcycle mechanic. Hmm, perhaps so.

Finally getting to the point, the acceptable quality of restorations in 1976 when Jeff Clew wrote his restoration book was considerably lower than when Radco wrote his just ten years later, and since then another 35 years have passed. Certainly, the acceptable level of cosmetic restorations has continued to increase over that time, but what about the mechanical aspects of restorations and rebuilds? Given that internal combustion engines are very tolerant of wear and abuse, so that rebuilders can "get away with" being quite sloppy when working on them, how should someone working on old bikes look at this? An aftermarket bush pressed into place might work OK as-is, but the only way to know if the resulting clearance meets the original published specs and it won't fail prematurely is with a precision measurement instrument. And the only way to deal with it if it doesn't is with a hone. However, are such things, out of sight, out of mind? Is time spent on the mechanical internals, beyond getting them "good enough," time wasted?

Beyond the pleasure that doing such precision mechanical work might bring, in monetary terms are you (me) wasting your (our) time? Are people who buy restored old British motorcycles today unlikely to put enough miles on them to reveal shortcomings in the mechanical work? Would someone pay any sort of premium at all to buy a bike with documentation showing details of the mechanical work, or is chrome and powder paint all that really matters? Does the average buyer of an old British motorcycle (as opposed to the average Youtube video maker) know enough, or care enough, about the mechanical aspects to even judge the quality of, say, someone else's work to install new guides and seats?

Basically, I'm hoping for an informed discussion of questions like these with people who do more than bolt parts together, which would mean people who at least own a lathe and mill. However, as I said at the start, it doesn't seem very many people on Britbike fall into that category so this could be a very short thread.

Motorcyclists, mechanics, machinists and precision machinists seem to form a Venn diagram with diminishing degree of overlap. A lot of motorcyclists are mechanics (trained or otherwise), far fewer are machinists, and very few machinists are precision machinists, so that's going to be a rather small subgroup.

That's always a tricky on. Later BSA and Triumph workshop manuals were quite good at providing torques, tolerances and wear limits, and I think most people will work to those figures. The rules of thumb for fits and tolerances for different materials are available, though not so readily.
Material selection and heat treatment is a rather more esoteric area, and often involves cross-referencing between not entirely compatible standards.

The question of "good enough" is another vermiform container. Production pressures meant that the motorcycle factories worked to the "good enough" level, which is really what the figures in the workshop manuals show. Competition shops blueprinted to some extent, but even then practical factors of time and staffing came into play.
When all is said and done, even the designs were compromises, often working to greater safety margins than necessary to allow for production line and maintenance realities.

After many years in the "mechanic" category, I finally have the time and space to put together a half-decent machine shop, and try to learn how to use it. As such, the machining discussions are quite invaluable, as are some of the Youtube channels (kommando, I quite agree about Joe). As magneto man said above, winnowing the wheat from the chaff online can be quite a challenge. Even the better examples on Youtube have blind spots which may not be immediately obvious without sufficient experience to know when they're wrong.
In other cases, it's obvious BS.

I spent a few too many afternoons at Doc's workshop as well, and felt it the next morning. It was all very exciting to somebody in his early 20s, but in hindsight Doc was a butcher. It's easy enough to make something go fast (for a while) with clearances on the loose side, and they obviously wore out quicker because they were thrashed, not because they were already halfway to their wear limits when assembled.
It's certainly possible to get within the fairly broad tolerances of the period by feel. In fact, the BSA Service Sheets used to be worded that way. If I have a choice, I like to have the numbers in front of me, though.

There's a continuum from "but it runs", through "mechanics" like Doc and Barry who largely worked by feel and the factories which at least had go-no go gages to precision engineering such as that done by RPM or Magnetoman.
When it's all said and done, "acceptable" is going to be quite sensitive to the intended use and individual sensibilities. Design limitations come into play as well. Having a pre-1930 motorcycle cover 3,000+ miles in 2 weeks is an achievement, just as it was when they were new. Doing the same with a late 1930s machine is much less challenging, and one would be rather disappointed not to do that with a 1950s machine, even a "grey porridge" commuter.
Having the occasional 100 mile weekend ride is different, and riding a 10 mile return trip to work every day is different again.

I’m logged in here after browsing Sunnen honing machines on eBay…

I’m a machinist…

I own John Edwards textbook, and have had him do work for me (RIP)…

YouTube is spilling over with people needing attention and affirmation. My opinion is that the folks that know how like to guard their knowledge, or are too busy to make online tutorials.

Finally, it’s frustrating to participate when sound advice is drowned out by the peanut gallery regurgitating something they read elsewhere on the internet (really bad on the Facebook groups) or the same peanut gallery sharing pictures of their bike even though it has zero relevance to the discussion (also really bad on Facebook).

It can be horribly time consuming or expensive to make certain repairs correctly. It’s far easier to refinish something to look nice and leave the finer points of the mechanicals out of sight, out of mind.

Chris

Magnetoman,

First post ever here,

I finally felt compelled to respond to your thread, having read and enjoyed your articles as an unregistered reader over the last decade or so, and which in my mind are the highlight of these pages.

As a toolmaker, enthusiast, and professional engine builder, your articles are an absolute delight to read and an education for anyone who wants to do a job right. Your magneto article for example is an essential read for anyone who has any interest or need for a mag which is going to make sparks every time and for a long time.

Frustratingly, I find it very difficult to sub contract any personal or professional work out, as it seems on a high proportion of occasions the result is less than satisfactory and does not meet the standard agreed and discussed with the provider, and this extends beyond engineering and motor vehicle parts..

The ultimate fact is an engineering product or service you provide and especially one for remuneration carries your name, and in my mind not only has it to do the job as intended and agreed with the buyer, but also has to be able to stand the scrutiny of others, who may for whatever reason may find the time or reason to unpick your work, and subject it to the scrutiny and tests to see if meets an acceptable engineering standard.

Clearly the use of precision tools and equipment is the only true and sure way to achieve the acceptable standard each and every time, and the work of the production Engineer depends on this approach. However there can be no doubt too that there are also many examples of outstanding work which has been produced with only the most basic tools and circumstances and is a complete credit to the skill of the Artisan.

It’s very hard to see any reasoned argument against your approach to your projects, and I appreciate your devotion to document and record it for others to enjoy. How anyone attends to the maintenance and repairs of their own machinery is their business of course, but really there is no need to knock your approach, even if theirs is different..

Roland

First, thank you very much for your kind words. However, for anyone who hasn't noticed, this certainly isn't the first of my threads that Rohan has trolled.

Offline someone wrote yesterday to say my posts have shamed him into doing a far more thorough job on his rebuilds than he used to. Hey, anytime I can bamboozle someone into squandering more of their time and money than they otherwise would have I count it as a success.

I don't think everyone understands that it can be horribly expensive just to return many things to as-original specification. Also, people who buy into the urban myth about the Bronze Age quality of the original machining don't realize how much improvement to lifetime and functionality can be made by simply blueprinting the the engine and gearbox, i.e. making sure they have the specifications the designers gave them. I suspect Alp Sungurtekin didn't go 175.6 mph on a pre-unit Triumph without having done more than just bolt the engine together.

To go one step further I have difficulties with people who don't know how to ride the bikes they have anyway.
No matter how carefully put together if the person doesn't know how to operate it as the factory intended then you have an unhappy marriage with everything being blamed except the riders lack of knowledge. Woe betide the person who tells a fellow motorcyclist he doesn't know how to ride
.
Modern motorcycles have more or less standardised controls. You can move from one to another expecting to find the basic controls, brakes, clutch, throttle, etc in the same place and working in the same manner.

Not so with earlier machinery, Not only can the controls be wildly different they often doesn't respond well to a new rider trying to modify these controls to suit their riding style rather than them changing to suit the bike. The classic case in point is the modern self closing twistgrip throttle. This is not a happy combination with either a hand gear change or the need to give hand signals (not that many other road users appreciate them anyway) and certainly not with an elderly two-stroke lacking an ignition key where the engine is intended to stop when the throttle is closed. I have an ongoing role explaining the reasons behind the adjustable friction screw on Amal twistgrips and that twisting the throttle off as well as twisting it on can make for a much more relaxed riding experience.

All in all I think a high proportion of older bikes aren't ridden that much because the owners don't know how to.

"Beyond the pleasure that doing such precision mechanical work might bring, in monetary terms are you (me) wasting your (our) time? "

No, personally it gives me great pleasure to assemble mechanical stuff with the correct fits, I like to think that it will make the bike better to use.Usually this involves refining poorly made parts so that they will operate correctly.


"Are people who buy restored old British motorcycles today unlikely to put enough miles on them to reveal shortcomings in the mechanical work?"

Sadly , yes, in my LBS I have seen several examples of old bikes which were only fit for gazing at in the garage, new chrome and paint, dreadful mechanicals.



"Would someone pay any sort of premium at all to buy a bike with documentation showing details of the mechanical work, or is chrome and powder paint all that really matters? "

If i was in the market for an old bike , yes , definitely to documentation, I would be put off by shiny chrome , particularly exhaust pipes.


"Does the average buyer of an old British motorcycle (as opposed to the average Youtube video maker) know enough, or care enough, about the mechanical aspects to even judge the quality of, say, someone else's work to install new guides and seats?"

Thats a tough one, very few purchasers would be in the position to strip a motor prior to purchase. i would view any potential purchase as a potential grenade unless it came with receipts from Phil Pearson, or some other bona fide specialist marque machine shop.
My own interest is unit twins, i paid over the odds for my current bike because I knew the motor had been built by Devimead.

Random post to test the inline embedding function.

Will delete soon.

First bird-caged cable end this a.m..
Cheers to Cyborg for his tip on Laphroaig 25 Year as a quench.
Does give it a lovely nose.

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Given that most of these old crates were produced on machinery that would
be termed scrap by some people's standards my own feeling is that spending
inordinate time and money sending my machine work to the National Physical Laboratory
will never make these things much better than they can be by just applying general
good practice and accepting there faults. Blokes who remanufacture engines as a
facsimile of what they were are not ending up with the genuine artificial anyway.
For example, how many goldies did Phil Pearson build at BSA using genuine bits and
their machinery?

A ford Cortina rebuilt by Cosworth/Vandam Plas is still what it is,,,, a Ford Cortina.
Some people will obsess over stuff but others just don't worry about it.
Some people love to lecture and make youtube videos telling everyone how clever
they are, other people would just rather ride their bikes.

Back in the day BSA by & large used steel tooling that traversed a fixed distance between two stops or till the turret tripped the cam and rotated the tool holder . And most likely plain high carbon steel to boot as tool steel was expensive back then and carbide only justified for defense work .
As such, the tool movement was the same , hopefully , each & every time .However this tooling did not take into account things like heat build up in the job & tool nor tool wear nor tool pick up or even the ambient temperature and particularly in the UK stillages full of metal parts that have been sitting in the open courtyard all night so are at 2 deg when clamped into place.
Thus no two parts were ever identical which is why each & every part was gauged and usually stamped.( what does this funny star mean ? )
Now when assembling the bikes the parts could be blueprinted for want of a better term to match over sized shafts to over sized holes thus hopefully yielding a motorcycle with everything within reasonable levels of fit that today would have the bike sitting in the line at the mechanical rectification station. And I seriously doubt the go-nogo gauges would have been measured to an accuracy of +/- .001" let alone +/-.0001"
Also remember they were built to a price not to a quality standard , one of the contributing factors identified in the decline of the UK motorcycle industry.
And where they were built properly ( eg Some Gold Stars ) then they either costed substantially more or were sold at a reduced margin or even a loss as again more than one historian has pointed out .

While it can be beneficial to repair parts to a tollerance far tighter than BSA did , the burning question is of extra cost vs utility.
Now if I was considering to do the WA to NSW cannon ball run or I am a person such as Mark Parker who's thing is to push the envelope way past what BS A intended then it may be a worthwhile use of my time .
However as most of us do the odd rally & occasional Sunday ride with friends/club members then we have to justify weather cutting seats with a very expensive & time consuming Sunnen machine ( or similar ) that we use so infrequently that it takes a full day to do a 10 minute job against the surface finish from a set of Newey cutters that require very little skil and even less time would be just as good for our purposes ?

One only has a finite time on the planet so one has to choose weather spending a large chunk of it learning a new skill that will get very little use is justified againts being out there riding the bikes .

As for You Tube being populated with shaved monkeys with over active egos & under active brains , well yes I have to concur that the bulk of what is on there is trash which makes life difficult if you don't know any better and were actually trying to get proper instruction.
Mechanics ( in NSW at least ) used to get basic training in machining , heat treatment , metallurgy & surface finishing , for a few years I taught the odd class in some of those subjects and to be quie frank it was a waste of their time, my time & taxpayers money .
They used to get basic foundry practice & blacksmithing too but both had been dropped before I got there in the early 80's .
TAFE courses change to reflect what is the actual shop floor practices & by the 80's it was just measure & replace where needed .
Shane & I found his out when we were trying to find a maching skills course to enrol in.
Not any more it is water jets, plasmas , erosion & CCM

Then there is the question of precision tooling vs the calibrated wrist.
I can usually set mower engines to .004" valve lash +/- .001 by feel as it is a daily task and can tell if they need to be reset by the sound of the engine cranking & running . If you go back & look at the British Pathe' movie inside the BSA factory note the assembly production worker tightening the A 10 con rods. no tension wrench, pure feel & experience. Note also the book end piston ring compressors & the fact they cranked the pistons up into the cylinders as distinct from trying to drop a heavy cylinder on the pistons squarely as most people do. Which would you call the better praqctice ?

Then there is the difference between doing it for fun and doing it to eat
The old addage of " I can do it good , I can do it cheap , I can do it fast, - but only one at a time " is God's own truth when you are trying to make a living from mechanical repairs
I can remember spending hours polishiing microscope specimens down to 0,5 µ cleaning all the old diamond dust off the cloths, before starting & between samples suiting up in disposable PPE with hair caps in uni lab sessions to take perfectly focuses micrograps without a blemish, then I went into industry where it was 5 minues a hit . one 2 oz tube of paste per 100 samples and specimes like rail crossings , just so long as what we were looking for could be identified &/or measured as these had to be costed and some one had to justify that cost .

The trick as I have learned in being a mechanic ( well tech actually because I was not apprenticed ) is to know what the customer wants
Good, fast or cheap and in most cases it is cheap so cheap dictates that stuff I do not regularly do or can get done cheaper, like rebuild Hydro drives gets farmed out the person who does them all day every day & I get back a ready to instal tranxaxle for less than the wholesale price of the rebuild kit and 1/4 of e price of a replacement.

Before it became illegal to straiten motorcycle frames down here I have had 5 SR 500's bent back into shape
3 by the Aldersons who did the whole thing by eye using long levers and 2 at a workshop using one of the Motoliner with jigs & rams
Dennis did the job same day for something like $ 100 while the motoliner was around 3 times the price & took over a week.
The proof was in the riding & the hand done frames rode a lot straiter than the jigged frame did.

If a workshop down here was to have done what you did to your Ariel then the bill would have been close to $ 50,000

When buying from an auction, or private party, one should always take into consideration the phrase: "as is, where is!"

When i was racing i competed against quite a few blokes that used to take their engines to
named engine builders/tuners and bore the huge costs incurred. Those motors would have
rods replaced every xx hours etc etc and were 'blueprinted etc etc. I don't remember any of
them actually winning championships against the many that did all their own work and used
their own practices to build engines and gearboxes. I've ridden a few bikes that were prepared
in that way and in all honesty, i could not tell the difference between a 10,000 quid engine and
a 3000 quid engine as far as how well it went and sounded. Like many here i don't expect these
old things to do huge mileage before requiring rebuilds, they were designed that way. i feel
happier knowing that i put it together rather than someone i don't know. Yes i check all the important
stuff but putting your own 'take' on assembly (which i like to do) is what it's all about, blueprinting
means building the thing as the factory would have, and with the old irons i own, that's not that
good. As for stuff like boring with torque plates fitted, i'v'e only ever done that when racing, the
possible 0.5 thou extra wear at 20,000 miles never concerned me. Things like trying to improve
valve geometry and compensating for poorly designed gearboxes does. Blueprinting would have
those assembled as per the design, not what i would want.
Finding shops that are interested in 'one off's' is harder these days as all the old boys are dying or
packing it up. It will become a lost art soon. There's little money in one or two cranks for old
beezers as opposed to hundreds of hondas.
But hey, each to his own.
Nick

Back to the top, I think.

I do have a lathe and mill. I did go to school for machining and did my time making injection molds and such. Then off to a better life in mechanical inspection and metrology. Back to school for mechanical engineering....


Would folks pay more for something well documented ?

Yes, I'm sure of it.

Would I document in great detail a 50 year old + bike rebuild with plans to turn it over to the new owner and maybe get compensated for my effort?

No way.

Perhaps the biggest reason would be liability. Something, someday, will go wrong no matter how much care is taken in assembly or what the new owner may have done, and my name will be on it. The new owner will then take it to some hack Britbike mechanic and flip to page 59 of the documentation package and say; "Look, right there is where he screwed up and that is what wrecked your engine"

I just don't think it is worth the hassle.

But surely the point is than very few want or need to go 175.6 mph on old British iron.
One of he reasons why old British Iron is so heavy is it was grossly over engineered in the first place.
The fact that so many are still rolling around 50 to 100 years after they were made is testiment to that fact.
Have a chat to any racer about just how much can be shaved off most of them with a reasonable certency that the bike will finish a race.
And as to bronze age quality , I have just gone back through Vanhouse which was just as well because my recollections were wrong.
The tollerances on parts, at least up until 1952 when BSA won a Maudes trophy were so wide that it was still considered a feat to be able to assemble a bike from spares bought over the counter and have it actually run and that speaks plenty about the general precision of availible parts when there bikes were new.
Back when I was a school & working part time in factories there was a trades qualification called the "fitter-Turner" and the "fitter -machinists"
The turner / machinist refers to the fact that parts were not expected to fit without modifications.
Indeed the pulleys we bought for our Victa powered mini bikes came with nothing more than small pilot hole for the shaft and a raised boss for the grub screws.
The customer was expected to drill the hole to suit the shaft of what ever the pulley was going onto.
Fifteen years latter on when I entered the workforce full time this trade had vanished as parts were now very much plug & play.
The old mechanical workshops would have a lathe against a wall some where that was never used unless a part was NLA.
As for measuring tools, I learned to use & read micrometers & verniers in high school but never saw one on a shop floor anywhere apart from the clutch & brake workshop who use verniers to measure the diameter of brake drums & micrometers to measure clutch plates .

Perhaps top end tuners churning out land speed record attempt motorcycles would use precision measuring for valve guide clearences but for most workshops , no rock is more than good enough.
I can remember spending a few too many afternoons in Doc Kellys Speed shop who specialty was making very fast Triumphs , all done by feel.
The only measuring tool remember seeing was what looked like a modified depth gauge that he used to measure bores with , a circumference band which he used to measure rings with and loose feeler strips
Places that had things like micrometers would keep them in locked cabinets only to be signed out by the supervisor or foreman.

As for things like valve guides the only "test" I can remember seeing been done was the thumb test where the valve would be oiled and dropped into the guide then raised up a second time and dropped in while the mechanic had his thumb blocking off the rocker end.
If the valve remained suspended by the air pocket but dropped strait down when the thumb was removed then the valve guide was clearance was fit for purpose.
Those who have to see numbers might be horrified by this type of approach but those who do the job day in & day out have the experience to know by look & feel , much like the calibrated thumb in the plug hole compression test.
Some where there would be a Vickers number ( Brinell would be better ) for dead soft copper so one would know if the head gasket was fully annealed or not, or you could roll your thumb over it and see if you thumbnail can leave a full crescent indentation .
While there is nothing wrong with fine precision, it costs time & money some have both in spades while others have neither.

Back to the question of pretty vs mechanically perfect, again just going on my recollections of what I see on these pages
I remember a lot of people requesting help to find the best spray painter or where they can get perfect plating .
Add to that endless posts about the merits of dipping vs spraying vs powder coating

Not quite as many looking for the best machinist so the obsessision would appear to be well & truely baised towards the pretty
People post pictures of their bikes & carry on about who painted them where the mufflers came from etc etc , rarely a world about internals

All I can add is......personally I would pay a premium for ANY bike you worked on. You wouldn't have to show me any proof of methods.....period.

In our small circle.......you'd fit in that "famous owner" category.

Gordon Gray in NC, USA

Well thats a couple of hours I won't get back.

Magnetoman,

Just to pick up on this point. Back in the mid 1990’s we decided to setup a new business to remanufacture components for British 1950’s engines ( not motorcycle), and from the outset we went CNC and specified them with Renishaw probes etc, so we could reference datum’s on previously made parts.

We have never looked back, and we would have never survived, let alone thrived without going this route. Many people thought we were quite mad going into a declining market of engine rebuilding as it was, and the idea of automation, production techniques and tooling etc to do very low volume work dismissed as crazy.

Our secret of course was to stick to a limited catalogue of engines and components which we know well and of course this way, we could tool and jig up and of course we know all of this issues they have in service. For example as we can incorporate adjustment of tolerances, such as to deal with a known tendency for a particular piston / cylinder on a multi to seize first should the engine overheat, so set that one up on top clearance, and so on.

The Jobbing machinist / engine man has of course a much harder job all round, as every customer coming through to door brings a different problem. I would maintain CNC can and often is still a better tool for one off’s as the ability to generate cutter paths such as for valve seats with simple tooling saves on inventory. Swinging a rotary table etc old school can be done, but is an expensive lump of kit mostly found lucking under the bench doing nothing, and a workout to use too!

However, we will always have a place for our Adcock & Shipley license built Bridgeport, sometimes it is just the tool and really there is not much you cannot make on the simple screw cutting lathe should you need to set you mind on it. The Sunnen (Delapena in the UK) hone is worth its weight in gold, and a key element to any jobber’s tool room. This is of course if you care about 10’ths and the surface finishes of holes you finish.

You are not entirely alone in the quest!

Roland.

This is a good question. Maybe this helps, two jobs come to mind. Bear in mind I am not suggesting everyone should have CNC at home! But if you are trying to earn a crust as I am, this is my reason why CNC is good for us, and perhaps is of interest.

Firstly your valve seat pocket. On a 3 axis machines like we run, you would have to get your valve guide bore parallel with the spindle. Fixturing is always a time component no one enjoys having to pay for, and this element is the same for a manual operation or 3 axis setup (Though you may make the fixture in situ if possible). I suppose with a 5 axis, have the machine probe the guide at two depths if it’s something like near parallel with the spindle to start with and with a bit of trig let it work out and move to the correction, or if you felt less inclined to write the code to do this, just jog each of the sub axis and get square to the spindle manually.

However, from there, rather than bore with a manual head on your mill, with tool push off, risk of going over, and I recall you had a devil of a job on your project with hard spots, a simple stock diameter rigid carbide end mill say 16MM – 20MM dia will generate a sharp square pocket without taper, push off and of course the probe will find the diameter as you progress and adjust the last cut etc, all whist kettle can be on for a nice cup of tea.

I would argue this would be a winner for me on this job, as it would be a certain outcome. Programming time to make a counter bore is seconds using a canned cycle.

I have a job on right now making a set of custom designed flywheels for a short stroke single project. I would class this job tolerance as jig boring work if assigned to manual machinery. To make one set by hand would be tedious. To make 2 sets and a spare, the will to live would be lost. The time to machine - what is quite a complex balance cutout profile, crankpin detail, main shaft location detail, then turn the job over and rinse and repeat. With a CNC you can do this, turn the job over for second op, eye it up something like near, probe the main shaft hole, probe the crankpin hole and let the machine skew the second op program square, rather than fiddling around on a rotary table. I am sure the time saving here would extend to days rather than hours, and far, far less risk of mistakes.

Roland.

I could see that coming.

Not sure where I fit in on the original question as I have years of precision toolmaking experience and have been running my own business for 25+years with our work sent to different parts of the world. Having said that and despite having a fantastically equipped workshop at my disposal, I only make bike parts for myself, I've no commercial aspect with engineering and my old bikes. Despite all of this experience & equipment, I'm just as much at the mercy of "experts" as anyone else is here, for example, I had a B25 crank ruined by a bad machinist when it was re-ground with more than a thou taper along the width of the big end! I buy plenty of parts that I could make, if I really wanted to, but I don't see the point unless it's either unavailable or the quality is not as good as I think it should be. Why go to all of the bother making con-rods, for example, when there are some very well made ones readily available?
The main area I'm focused on these days is cylinder heads and in particular seats and guides, below is a picture of an experimental 74 T120V cylinder head that is nearly finished. The 74 T120V 9 stud heads are unusual in that they use the T140 10 stud casting (71-2863) that are machined with a 650 style chamber that is smaller volume (higher comp) because the 1.355" radius of the hemisphere was lower and there are two smaller hemispheres concentric to each valve seat. The T140 chamber was a single 1.355 radius that intersects at the same point of both valves, making it much easier to work on. The valve guide support is longer version with shrunk in valve seats, just the same as the T140 and to my mind they're probably the best 650 head because of this...if you can find one!
My T120V head below.

As far as removing the valve seat goes the problem on Triumph B series heads is the 45 degree guide angle means the heads tilted so much that access becomes an issue, although I've CNC machinery it's not a lot of use unless it's full 5-axis. I made a fixture very similar to the one John Healy has shown previously and even then it's tight. Serdi make seat removal cutters but as far as I know they are fixed to suit a particular size, anyway I've some Swiss made adjustable twin insert cutters and they will fit the tight gap and remove the seat in no time at all. The alternative is to use a single point 90 degree cutter although I only use them as a blank to make my own seat profiles.
The picture below shows two cutter types for seat removal tool and the lack of room available.

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I use TouchDRO on a tablet, its an Android app and one of the parameters you set is machine type, set it to Lathe and you can select radius or diameter as the reading on the X cross slide. The glass readout slide on the Y axis reads to 5 microns and the display resolution can be set to this if needed. However DRO or not the issue of checking after each cuts does not go away, tool deflection differs with cut depth and also you have tool tip wear as well. Internal boring is the worst with large tool overhangs, just take a second cut with no tool movement and you will see metal being cut showing the tool deflection of the first cut.

My original post already was too long, but it was too short to properly qualify all statements. But, I don't see how anyone could believe I simply lump people into just those two categories.

No, you've made an incorrect inference. It's common practice for a mechanic to provide copies of receipts, or an itemized list of out-of-pocket expenses, along with their bill for labor. It's not patting themselves on the back to provide documentation for the $20 to buy a valve guide, so why would it be for providing documentation showing how they installed that guide?

That's certainly a fine approach, but it gets back to one of the questions I raised. How do most people know someone is a craftsman, and how do they know they will do it correctly? Just because someone has been doing a job for many years doesn't mean they might not be doing it the same obsolete or incorrect way they did it at the start of their career.

One example of the perils of sending things out to craftsmen happened to a friend of mine, whose magneto had 'packed up'. He sent it off, had it 'rewound', which is what the expert said it needed, only to have it pack up again within 300 miles. My friend was so trusting that he was about to send it back to the same guy until I, and a number of others, staged an intervention and persuaded him to send it to someone who really knew what he was doing.

I have a Phil Pearson crank that I am soon to install into two new John Cronshaw Gold Star crankcases. I know John Cronshaw's reputation from other friends, one of whom built a Gold Star trials bike around a Cronshaw engine. Before he retired, Phil Pearson was one of the best-known BSA engineer/machinists in the world. At the bottom of the engineering pile is me, who will be bolting it all together. If I don't screw up too badly, I'm hoping that the premium I paid for the work of these renowned experts will get me out on the road.

Oh boy oh boy, is this a problem. We are down to two machine shops in our town. Neither one is full service ie crank grinds, line honing or line boring or even hot tanking. I have to send some jobs 60 miles away and others even farther. A recent BSA A10 crank regrind cost me $350.00. I do almost all of my own work and know enough to recognize acceptable work. I have literally taken my mikes with me to pick up machine work from well known "specialists" only to find incorrect (undersize) journal dimensions on a reground crank.

So IMO, the only way you can know is by your own track record and relationship with the particular specialist. But even that is no guarantee. I've been taking stuff to some of the same guys for years and frankly, I have occasionally just eaten substandard work in order to preserve the relationship. And the fact is, even the best guy can have a day when something didn't go right.

If I want to know how to apply a new technique to repairing or making a part on my mill or lathe I use YouTube but only experts in lathe or mill. Never look at bike mechanics working with machinery as they are not experts.

So first go to guy

Joe Pieczynski

https://m.youtube.com/channel/UCpp6lgdc_XO_FZYJppaFa5w/featured

Maybe that's because I worked in automotive manufacturing for 35 years as a qualified engineer even though never as an engineer. I never applied my qualification directly but knew enough to know [***] at 100 paces.

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I suspect Alp Sungurtekin didn't go 175.6 mph on a pre-unit Triumph without having done more than just bolt the engine together.



Yes, i bet he just blueprinted it eh?

In the olden days of manual cameras and Kodachrome film it would have been difficult and expensive to document everything, but with today's digital auto-focus, auto-exposure cameras and phones, and inexpensive color printers, it would be easy and cheap. Yes, things could be faked, but that's an issue even for simple things (e.g. you could be charged for changing the oil and filter on your car, when the work was never done).

So little?...

At the Irish Rally people show up in the middle of nowhere (Killarney), ride their bikes for a total of ~500 miles over four days, do any necessary repairs at night on the wet asphalt (it's Ireland) of a car park using whatever tools and spares they have. Because of this, especially for a foreigner, lack of reliability is a real problem.

I once mentioned to a well-known dealer (who shall remain nameless) who is a regular attendee that there could be a market, at a premium, from foreigners for bikes guaranteed to be in good condition. He replied that his customers loved being able to fix things on the bikes they bought. Needless to say, I wouldn't let my worst enemy buy a bike from him… OK, that's not correct; I'd actually encourage my worst enemy to buy one of the guy's bikes.

These old things are all destined to be unmovable museum pieces in a few
years anyway thanks to the green brigade. Go and thrash the hell out of any you
own now as pretty soon they'll be either melted down or in glass boxes.

I own a 70 year old lathe but no milling machine....In the last 7 years or so I have built from the ground up aTriumph race bike, a double engine Triumph race bike, a 70 Triumph and 79 Triumph modified street bikes and a BSA A10. All these bikes were built in the American hot rod tradition,stripped of frills with increased engine performance and built from whatever parts suit the situation...You can see much of the work done right here on Brit Bike.Other than actual engine machine work, I did it much of it with hand held tools and blacksmith techniques...But I have cut piston valve clearance notches , honed cylinders and refaced tappets by hand..
So...What do you want to discuss? . Seriously, I have learned something from just about everyone who posts here...Even my wife had some good ideas...

My list of specifications says 0.002" for the inlet and 0.0025" for the exhaust. Although I subsequently improved my tooling significantly with a ball head cutter, with my Neway cutters I achieved a seat runout of just over 0.001".

Unfortunately, the breakdowns show me that my work was only almost good enough.

And the problem with this is the same one I have with the mythically perfect "machined from solid billet " CAD parts, is what ends up happening is the shop owner puts a $ 10/hr dullard on the end of the machine to recover the costs as quickly as possible because the machine can not make a mistake, till it does, but the operator who does not know any better keeps on feeding new parts into the machine & pressing the buttons turning good parts into scrap, some thing I have seen countless times in industry.
Or he puts a $ 50 /hr technican on the end so prices himself right out of the market because the number of customers who are willing to pay the same for a valve guide machining as a replacement heat ( remember we are talking about old British motorcycles not F1 race engines ) would be pretty close to zero.
And that is assuming that some one has programmed in the specifications for a 1943WM20, a 1973 B50MX or even a 1928 Ariel all of which would be very doubtful .

And of course we are now going in the endless circle.
Precision costs money and the cost rises exponentionaly with every order of magnitude
So then the costs have to be weighed against the benefit in one of those things accountants & political lobbyist love, a cost benefit analysis .
Do I want a bike that will go just fast enough to outrun the local police & occasionally win a drag against my circle of peers ?
Am I happy for it to self destruct just so long as I can be the fastest on the night ?
OR do I want it to run for long distances with a mean time between failures that could only be dreamed of when the motorcycle was new
Or do I want to ride a "Budget Brit" for the minimum outlay & maximum fun ?
Will the fine precision last long periods of storage or will cams. cam followers. bearing races & rolling members end up either corroding or Brinneling due to not being used , or valves sticking due to corrosion from lack of lubrication cause by lack of use, let alone things like stiction caused by oxide growth over time , and of course wear from actual use itself negate the fine precision used in the remanufacture ?
Right down to the question is turning an old production bike into something that would have cost 5 years wages back in the year it was made so would have never actually been made, is being true to the ideal of riding a historic vehicle or are you really just making a hot rod without the extensive body work changes.

All very personel questions that will have a different answer from each & every one of us so none will ever be universally applicable.

Then when talking about precision in the orders of 0.0001" or the implied +/-0.00005 just how accurate will that actually be be when the simple act of touching the part or even measuring the part can cause enough temperature change to affect the reading so of course those reading will need temperature compensation and at that level of precision the difference in the thermal properties of the actual different grades of steel come into play let alone the temperature of the workshop & the presence or absence of any breeze that may be in there and the temperature of said same breeze and of course the temperature rise caused by the maching process itself regardless of what type of cooling is used .

Does a valve seat that is 0.010 wider than it should be really affect the performance of the engine ?
Well to all effects & purposes the answer is no. There is probably a point where there will be insifficient clamping force to prevent leakage but at what seat area ?
In theory it will transfer more heat & cause the valve to run colder than it should and reduce the sealing pressure so make it more prone to leaking ,,, in theory
The burning question is does it make any difference in practice in the actual engine, so a 13:1 dope burner running at 10,000rpm probably but a 7:1 street bike, not likely and a 6:1 SV no way ?
A valve guide true to 0.00001" is fine, but the valve does not heat uniformly nor does it expand uniformly and of course we can all appreciate that the stem itself will become conical from the effect of thermal expansion so the cold assembly precision can quickly vanish at operating temperatures

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I own a small RANDA lathe and pillar drill and various other tools so I hope that gives me enough qualification to try and answer question. I don't use these tools for precision mechanical work as they aren't up to the job, they are however OK for making spacers, drilling out holes etc.

In order to answer the questions I've broken them down individually as shown below:-


Given the cost of farming out work to various machine shops, I would say you are not wasting your time and money especially when you consider that the work will have been done exactly to your own spec.


I think that would depend on how the bike is ridden and subsequently serviced. I imagine that most riders will ride less than 1000 miles annually and for most of the time the bike will be sitting in a warm garage and get an annual service. On the other hand, some riders will thrash their bikes relentlessly, pull wheelies and rev the bike past the red line and try cruising on the highway at 90mph. I guess that the former type of rider will not experience any mechanical failure for at least 15 years whilst the latter will probably blow the engine in a year or so.

The issue here is not so much the quality of the restoration but the fact that British bikes are fragile and don't respond well to mistreatment.


Yes I would pay a bit more if for example the bike has recently had new valve seats & guides inserted, aligned, diamond honed etc. by a renowned company such as the Cylinder Head Shop, and there is documentation to support this.


Some will and some won't but overall I think most will be happy enough just seeing an engine running with no apparent faults.

I have to say MM, you postings about the Ariel and other restorations have been extremely interesting and informative. I think you have raised peoples engineering knowledge and awareness considerably over the last few years, and who knows this may have helped to raise standards going forward. As Trevor said, I don't know how you find the time to do your machining, photograph each step and then post an almost daily update, I'm sure all the effort is appreciated by forum members.

I was hoping to read more about the Black Shadow restoration, but as you know, the VOC forum seems to be in turmoil as they try to migrate to another platform. Other than using this forum, I don't know if there is an interim alternative, but it seems like the restoration is stalled whilst you await clarity with the VOC.

In the days before mobile phones, the fact that you could quite happily ride a BSA twin for 100 miles or more on one cylinder provided you did not push it too hard was a big +. Try riding a Honda 4 on 3 cylinders and see how far you get .
So fragile they are definately not.
Coming from the age of log table & slide rule engineering, when proof could only be done in metal most British bikes are way over engineered for their invisioned use because the factory could not afford to engineer them to fail completely the second warranty expired like can be done now days . It is only in modern times of computer simulations where with a few key strokes on the right softwear work out the consequences of making the casting thinner in 0,001 incriments or sit at your desk and investigate timing variations measures in radians .
And when it comes to carburettors you will never get any modern carb to even start a bike if they were worn or mal adjusted to the level of a lot of concentrics I have seen on a lot of members bikes , running quite happily

Aw, you make me blush.

It sounds to me like you are looking for feedback from machinists, as you seem to group anyone who doesn't own a lathe or mill with those that simply "bolt parts together". I think there is a wide range of skills that span much more than those two groups. For example, I've taken motor parts to guys who have been doing this work professionally for longer than I've been alive (and I'm not that young) and most of them sent parts out to professionals. Not your typical "bolt parts together" type of guys, nonetheless

I think this plays a big part in it. At, say, 1000 miles ridden per year, my BSA engine could blow itself to pieces at 20k miles (rather than the expected 25k miles ) but that puts it at 20 years out.

I doubt it, and here's why:
this would then assume that anyone who doesn't provide this documentation is a hack. Or, any documentation you're not able to provide indicates you're trying to hide something. That's 100% not the case so anyone who's providing the documentation is patting themselves on the back but, unless they're linking some type of warranty to this documentation, it's going in the file without spending too long trying to understand what it means.

I personally think more important than knowing how to do your own work is knowing when not to do it and send the parts out to craftsmen who will do it correctly. It's too easy to watch Youtube and think yourself an expert. We all have our strong and weak points and we all make mistakes. What differentiates the true experts is that they realize they made a mistake where a novice won't.

Yes you are jumping the gun there, Indian didn't get recirculating oiling (in the twins) until the mid 1930s.
Constant loss before then.

The catchcry in advertising was 'fresh oil every mile'. (And there is some truth to this claim.)
Even if it was a few drops.
(To which the counter-reply was 'recirculating sludge' for the new fangled fad of recirculating oil.)

Indians had very solid engineering in the crankpin and bearings and lower end.
(And frame and clutch and brakes and cycleparts)
A lot of english stuff was quite skimpy down there in comparison.
I've a Scout engine, which I bought simply to have a look at ...
The late 1920s 101 Scout model has been proposed as the best all round riders motorcycle of the 20th Century.
And not eclipsed for many a decade.

I'd comment that better metallurgy was the hallmark of the 1930s over the 1920s.
Assisted by the British Army insisting that motorcycles they purchased had to able to go 10,000 miles without an overhaul.
This prompted much research, particularly by BSA, that improved stuff, muchly...

We diverge, a bit, in the interests of accuracy.

I wrote that "a fraction" did their own work. In my defense, 99/100 is a fraction...

Machine work is too precise . I really like doing fabrication ,frames , suspension etc..using simple tools. This can be a job built to acceptable quality...and some guesswork...

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Maybe my treatment of bikes i own and have owned makes me feel that
engine rebuilds every 25-30k miles are the right thing to do.
I like to measure rod end eyes and suchlike before returning to service.
Probably if i knew they were ridden gently, that interval could be extended.
But that's not the way i ride them so i'm happy to do rebuilds.

You can't beat manual-operated machine tools for "one-off" jobs.

Unfortunately, it's getting increasingly difficult to find machinists willing to do these jobs.

While the cutting portion of the job would be faster with CNC, my upgraded tooling (which would have helped had I bought it before, rather than after, I cut the pocket...) would have eliminated the issues I had to deal with. However, it still would have taken me longer than CNC because I would have had to stop several times to reset the cutter to ever-larger diameters, and I also would have taken the time to measure progress each time I stopped rather than having the confidence of a carbide end mill and CNC program.

I can imagine the cutting process for that pocket with CNC might take a minute, but with my new tooling, plus my abundance of caution, it easily could take me an hour. While an extra hour for such a one-off job would make no difference to me, it would be money down the drain for you. Of course, once the time for fixturing has been written off by doing the first job, CNC puts you several hours ahead if you have to do even just one more.

Now that you've mentioned this, it will be agony not having CNC if I have to put 4 new seats in my Spitfire's head. Damn you...

When Dan Macias was machining heads for valves seats he had cutters for each seat with replaceable inserts that were ground to size.

Almost any seat size is available but he often made custom seats for old Ferraris from Ampco45 for better heat dissipation.
All that is old hat now with CNC. Extended nose tool holders get into a Triumph head no problem. Set up time is the same on a 3 Axis but the tools are set up before rather than during machining.
Spring pass - just click on the box, tell it how many times. Setting interference? Just put in the offset on the machine or program, run it, check the dimension, change the offset and push the start button again. Far simpler than manual.
Some things are impossible on a manual and simple on a CNC. I had to rechamber my 911 heads for RSR pistons (RSR heads are unobtainium) to bring the compression down for pump fuel. Put the new chamber shape into the program, tell it to cut the surface, put the head in the CNC, push the button.

Or putting threaded inserts into an A65 to have SpinRing pipe retainers, use a thread mill cutter, tell it the diameter and pitch.

New CNCs are expensive but if you are willing to put up with used they are far less and ones that need work less than that.There is a cost for all the tooling and three phase rotary. How much time and money do you spend just looking for a shop to do the work?
On custom parts such as valves and guides, I find it far more cost effective to find an auto part that is close and rework it. 7mm stem valves and guides for and A65? BMW M20 guides - 13.25mm O.D. cost $5, intake valve -1.651" head, 4.035" long, $8 from Bummer sources.
Of course, then mistakes are on you but at least you know it is done right (or wrong).

ahh. yes, I'd forgotten about that comment.


p.s. Perhaps if you start a new thread on the physics and engineering of motorcycle dynamics it will get a good discussion going after MM completes his current tutorial on precision measurement. It's certainly an interesting topic.