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BSA A65 Piston Suggestons? #3787
08/03/05 2:38 am
08/03/05 2:38 am
Joined: Aug 2005
Posts: 2
Southern California
H
hoohoohoblin Offline OP
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hoohoohoblin  Offline OP
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Joined: Aug 2005
Posts: 2
Southern California
I am new to the board, having recently acquired a 1971 BSA Lightning basket case. The guy I bought it from told me it ran before he took the engine out of the frame. I pulled the heads and found that one of the pistons is pretty beat up from something metal bouncing around on it. You can see pictures of the cylinder at my website:

http://www.hoohoohoblin.com/BSALightning.htm

As you can see, the inside of the cylinder looks pretty good, and the groove in the side of it from the metal object is more of a scratch. I could probably hone it and go with stock pistons. I'm going to have a local expert look at it and see what they think to be sure, then go with oversize pistons if necessary.

So my question is what kind of pistons would you recommend? I don't want to hot-rod the engine. I'm more concerned with reliability, rideability and reduction of vibration. I know you can buy pistons for Harley Sportsters which are lighter than stock, resulting in less vibration. Is there anything like that for the BSA? As long as I'm replacing them, I might as well upgrade.

Any help is greatly appreciated.

Thanks.


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1982 Suzuki GS650G
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Re: BSA A65 Piston Suggestons? #3788
08/03/05 4:04 am
08/03/05 4:04 am
Joined: Aug 2001
Posts: 3,348
Michigan, USA
BONZO R.I.P. Offline
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HOO , I'm not sure aboutthe Harley lightweight piston idea (if youre talking about an 883, they make great boat anchors , they seem to be balanced for a 1200 kit from the factory, otherwise they are just miserable ) , but if you are looking to upgrade a Britbike engine , you may be opening a large can o' worms . Piston weight , as far as I know , isnt the determining factor in vibration , having your crankshaft assembly balanced to match your pistons is a step in the right direction , and by '71 BSA was making some good strides in that direction with their twins , so if you arent looking at having the crank balanced , you might wanna look into a set of pistons that are very close to the weight of the originals , otherwise you may be moving in the opposite direction .Personally , I think the '71 lightning engine was about as good as a unit twin engine gets , and the more you tweak on it , the better it will run for you and a complete overhaul , including crank balance , will be a good investment . Loads of other things like carb tuning , ignition upgrades , engine mounts and hardware , and even chains and tires can make a big difference in the overall vibration of a britbike .

These things can be made into a sweet running bike , but you have to pay attention to a lot of details .

Re: BSA A65 Piston Suggestons? #3789
08/03/05 10:59 am
08/03/05 10:59 am
Joined: Aug 2001
Posts: 3,884
Cape Carteret, NC
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Mr Mike Offline
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Hoo,
I would get the manuals and go thru the whole motor and transmission. There is not telling what you will find. There are not many of those stores like "It ran great before i tore it down" that prove to be true. Parts are readily available for these nice old bikes.

Mr Mike

Re: BSA A65 Piston Suggestons? #3790
08/04/05 3:32 am
08/04/05 3:32 am
Joined: Aug 2005
Posts: 2
Southern California
H
hoohoohoblin Offline OP
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hoohoohoblin  Offline OP
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H

Joined: Aug 2005
Posts: 2
Southern California
Thanks for the info. That's exactly what I needed to hear. I'll keep it stock. I had a Triumph Bonneville 650 hardtail chopper 15 years ago, and I remember it vibrating a lot on the freeway. Fun to ride, though I often wished for rear suspension, a front brake, a speedometer, a tahchometer, etc.

I bought the BSA becuase it was one of the last BSA's, so it has some good features earlier models didn't have, like the big front brake and better oil pump. And I bought it because it was $800 and located 4 miles from my house. If I put another $1,000 into it, it should be a nice reliable machine.


Other bikes
1976 Moto-Guzzi V1000 Convert
1982 Suzuki GS650G
Re: BSA A65 Piston Suggestons? #3791
08/10/05 5:46 pm
08/10/05 5:46 pm
Joined: Apr 2002
Posts: 716
Out There!
N
Nick Offline
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Nick  Offline
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Joined: Apr 2002
Posts: 716
Out There!
If you're starting from scratch and want a trouble free, long running, low-vibe Beezer, here are my suggestions:

1. Send cylinder to Bore Tech in Ohio, and have them bore the cyl straight and round (very few places can do this correctly), then have them treat the cyl bores with their special carbide hardening process and plataeu hone it.

2. Once the cyl is done, call up Venolia or one of the other piston suppliers and have them make a pair of modern pistons with lower than stock compression (I used 8.5:1). Modern pistons come with modern chrome rings and 3-pc oil rings. In other words, you put the engine together with modern rings and a good cyl. it will run oil tight for as long as modern cars do.

3. Lower than stock compression means easier starting, less vibration, less crank wear and an altogether sweeter running bike with very little drop in performance.

4. Fit at least a 1-tooth larger than stock countershaft sprocket. If most of your riding will be on the highway, go 2 teeth larger. This will drop the revs at highway speeds, reduced vibration, improve fuel mileage and make for a relaxing and fast mile eater.

5. Get the crank balanced

6. If you're using the bronze timing side bush, have Bore Tech or other motorcycle machine shop align ream the bush and grind/plate the crank to fit (.0015).

I did the above to my A65 ten years ago and the bike runs perfectly, doesn't leak, hauls a$% and has had the same spark plugs in it for the past four years (starts first kick).
Use a Boyer ignition, as well.

If all this sounds rather expensive and troublesome, do a cheap rebuild and see what happens.

Good luck, read the manual carefully and stay tuned to this site.

Nick


When people who should have known better cautioned me about the dangers of motorcycle racing, I always told them that a fear of death is nothing more than a fear of life in disguise.
Re: BSA A65 Piston Suggestons? #3792
08/10/05 11:54 pm
08/10/05 11:54 pm
Joined: Mar 2005
Posts: 10,219
Boston, Massachusetts
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John Healy Offline
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Boston, Massachusetts
Modern pistons come with modern chrome rings and 3-pc oil rings. In other words, you put the engine together with modern rings and a good cyl. it will run oil tight for as long as modern cars do
-------------------------------
Modern chrome rings are not without their problems, and because the the face of the ring is not as wide as the old grey cast iron ring you will have less heat flowing out of the piston. These rings are looking for a water cooled cylinder bore, not a limited area air cooled cast iron cylinder. Also you have to be sure the top ring isn't moved higher on the piston typical to modern pistons design. Air cooled engine pistons run hotter than their water cooled cousins. With the less of the heat being removed by the thin top compression ring, the thin top edge of the piston above the top ring can over heat, turn "plastic" leading to the top of the piston failing or coming off.

The area just above the top compression ring is subject to extreme loading as the piston goes over top dead center. Piston engineers in these old bikes didn't just place the top ring just anywhere. There is a lot of thought that goes into this and the extremes of thermal overload, due to the nature of air cooled engines, had a lot to do with the width of the ring and where they placed it relative to the top of the piston.

Also to use these rings, and the cylinder finish they require, both the crankshaft and the crankcase mouth has to be square to the cylinder and I am here to tell you they don't come from the Triumph or BSA factory that way!

There is a lot more to this, but it is the end of a long day, I am hungry, it seems I am a bit grumpy smile and I am going home and eat some Cheerios and bananas.
john beerchug


Re: BSA A65 Piston Suggestons? #3793
08/11/05 12:15 am
08/11/05 12:15 am
Joined: Apr 2002
Posts: 716
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Nick Offline
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Great post, thanks for the info. Still, my A65 runs great--perhaps Venolia and the other piston makers know enough about the old bikes to locate the rings lower? Or, perhaps I'm not riding the bike hard enough for this to be an issue (hard to believe). Perhaps old style compression rings with modern oil rings would be the ideal solution......


When people who should have known better cautioned me about the dangers of motorcycle racing, I always told them that a fear of death is nothing more than a fear of life in disguise.
Re: BSA A65 Piston Suggestons? #3794
08/11/05 12:27 am
08/11/05 12:27 am
Joined: Aug 2001
Posts: 3,348
Michigan, USA
BONZO R.I.P. Offline
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Thanks for posting that info John , makes sense the way you put it , definitely on for the archives .

Any thoughts on ceramic coated pistons an nickasil(or simialr ) bores ?? I hear lots about the subject , but never from anyone who has tried it , and I am interested in this for a reliable long distance engine application rather than performance .

Thanks again -BONZO

Re: BSA A65 Piston Suggestons? #3795
08/11/05 12:48 am
08/11/05 12:48 am
Joined: Aug 2001
Posts: 3,884
Cape Carteret, NC
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Mr Mike Offline
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Nick,
All sounds like good advice to me. How much do those custom pistons go for? One minor comment...I absolutely agree with the align ream or bore on the bushing. I don't like to grind anymore off the crank than is necessary. If it needs a grind I take the minimum and polish. Some day cranks will be hard to come by so I take off the very minimum. I do not grind it to the specs the manual says. I then have my bushing align bored on a labratory grade vertical jig boring machine which produces a near mirror finish. Same result as you described, but I try and save a few thousandths on the crank.
Mr Mike

Re: BSA A65 Piston Suggestons? #3796
08/11/05 1:43 am
08/11/05 1:43 am
Joined: Mar 2005
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Boston, Massachusetts
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John Healy Offline
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Nick: Given that the work was done in a workmanship like manner these motors, which develop relatively very little torque, would be better served if their owners hauled a bit more a$$. Although not the buzz one would expect from a Honda, but certainly not the put, put, put of a Harley. 3 to 6 thousand rpm is a operating range that should give these motor the best chance for a long happy life.

I wouldn't count on the modern piston experts having a full grasp on this. We have had to have Aries move the compression ring down on the 500 twin pistons they make for us. I would post a picture to the list, but my last couple of pictures sit in the Triumph folder in a sad state.

I don't think the last word has been said about coatings. Especially thermal barrier ones. I think the experts are split on this one. What seems to be coming to a consensus is that wrapping the exhaust pipes is not such a good idea. But I am sure their still is contradicting thought about this on this forum.

Some of this stuff is like women's hem lines... fashion.
john beerchug


Re: BSA A65 Piston Suggestons? #3797
08/11/05 4:36 am
08/11/05 4:36 am
Joined: Aug 2001
Posts: 3,348
Michigan, USA
BONZO R.I.P. Offline
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John , I am a firm believer that revving an A-65 engine is a good thing , keeps oil flowing etc,,, and the things seem to thrive on it .What are our thoughts on idle speed? I have always been of the mindset that 1K is a good target for idle speed on a street bike , but lately I have been seeeing Britbike owners adopting the Harley philosophy that low revs is a good thing ?? On an A-65 especialy , with the dreaded T.S. bushing I would expect to see people wnting to keep the dle up and oi;flowing ??

As far a the plated bores and pistons, I have been tod that MFG's like Guzzi and BMW have been using these coatings for decades and it contributes to their longevity ?? I just wanna get a few seasons out of a well ridden BSA twin , but I'm not looking to toss $$ at the latest smoke and mirrors exhibit I come across... a wise man once told me , "I am too poor to buy junk" and maybe I should have listened a bit closer way back when ,,,,

Re: BSA A65 Piston Suggestons? #3798
08/11/05 10:42 pm
08/11/05 10:42 pm
Joined: Mar 2005
Posts: 10,219
Boston, Massachusetts
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John Healy Offline
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Boston, Massachusetts
The plated bores used by BMW and Guzzi are a bit away from the "coatings" debate. What they use are aluminum cylinders with a "Nikasil" plating on the bore. The rings run directly on the nikasil. LF Harris fitted Nikasil barrels to the Triumphs he made in the mid-eighties. This is not the same as coating the piston to prevent heat absorbtion. One of the problems with these ceramic coatings is the heat and cooling cycles of the engine tend to crack the cermaic coating. It can have limited life if used hard. There are other issues which can easily be found by googling.

I wouldn't call harleys choice of engine design a philosophy, but a logical selection of the engineering available a the turn of the century. Heavy flywheel, relatively small bore and long stroke. Horse power came from low rpm and high torque. This engineering continues today, although the bores are getting bigger.

Metalurgy had come a long way when Edward Turner started developing his verticle twin. It was probably the aluminum connecting rod, developed by the aircraft industry, that was the center of his designs. Horsepower came from low torque and higher rpm.

By the time Honda came on the scene metalurgy had improved such that motors could be built with many cylinders, small bore, and short stroke high revving engines. Horse power came from very little torque and a lot of rpms. Honda carried teh rpms to a point where with the racing motors 20,000 rpm wasn't unheard of.

Harley can sustain the slow idle because of the inertia of the flywheel, the Triumph/Norton and BSA etc verticle twins uses some of the flywheel weight, but like the horsepower the engine devlops, it relies on some rpm to keep up an idle. Honda's little 6 cylinders, 20,000 rpm motors, had no flywheel and idle was 12,000 to 18,000 rpm depending on the model. Much below that and they stoped running in what seemed to be one or two revolutions of the engine. No flywheel effect and 10,000 rpm to stop in what seemed like an instant.

Yes 1,000 rpm is an acceptable idle speed for these engines. Some TR6s can idle reliably at 800, but much lower than that you are asking for it to stall.

The dreaded timing side bushing is not dreaded by me. It is a perfectly sensible engineering practice. A bit fussy to fit and get right, but treated to an oil filter and routine oil changes it will last a long time. Although offered in a split format, plain bearing engines are basis of most modern engine design. I have a friend that has developed an verticle twin engine that reliably runs at 10,000 rpm, delivers 125 horsepower and is kitted up with bearings not unlike your BSA.

The failing, as I see it, is very few people know how to offer it properly to the case and finish once fit. See Nick's post above, done right, and treated to clean oil, they will last as long, or longer than a roller or ball.
john
Its home time again, wife is asking me what I would like to eat...


Re: BSA A65 Piston Suggestons? #3799
08/11/05 11:56 pm
08/11/05 11:56 pm
Joined: Aug 2001
Posts: 3,913
Houston Texas
Britbodger R.I.P. Offline
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Houston Texas
Another great thread! Nice to see you stepping out of the Triumph section to help those BSA guys John.

I do have to concur that BSA seemed to have got their act together in 71 as far as the engine is concerned (unfortunately too late).

My opion is based upon a ride that I had on my neighbour's brand new 1971 BSA Thuderbolt back then. I was really impressed! Although very pleased with my Triumph TR6C(that I still ride)have to admit that the BSA was so much smoother (and quieter). I was really quite envious! Mind you my Triumph had quite a few miles on it by then so perhaps not a fair comparison.

P.S. Do you mind getting back to the Triumph section John where you belong :p . We need you there.

Re: BSA A65 Piston Suggestons? #3800
08/12/05 12:18 am
08/12/05 12:18 am
Joined: Mar 2005
Posts: 10,219
Boston, Massachusetts
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John Healy Offline
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P.S. Do you mind getting back to the Triumph section John where you belong . We need you there.

I think they threw me out :rolleyes:
john


Re: BSA A65 Piston Suggestons? #3801
08/12/05 10:42 am
08/12/05 10:42 am
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Stone Creek OH USA
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Rich B Offline
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THanks John for your comments about the plain bearing bottom ends. It is a point so many miss when discussing hte A65. It is mainstream engineering in terms of bearings. It is a bit fiddly to get the bottom end right, and it isn't just bearing fit and end play set up. Bore alignment, deck alignment are also important.

And oil pump assembly, pressure relief, and pressure relief cavity are also incredibly important to making the A65 work. Filters go with out saying. It is my opinion that no Brit motor should be run with out adequate filtration. Screens will stop stray nuts & bolts and little else.

Idle, I try for my twin carb bikes to get a reliable idle around 900 RPM. It can be done. Doesn't seem to hurt them a bit.


Life is too short to drink cheap, bad beer.
Re: BSA A65 Piston Suggestons? #3802
08/12/05 9:24 pm
08/12/05 9:24 pm
Joined: Mar 2005
Posts: 10,219
Boston, Massachusetts
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John Healy Offline
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On a recent visit to Don Hutchinson (the paint guy) for one of those chew and chat sessions BSA crank cases was the nights topic. We scattered a half a dozen around and did some exploring. One of the first things we noticed is the location of the by-pass hole in the pressure relief cavity in the early models. It seemed to us that one wouldn't have to be that clever (stupid) to block the by-pass return hole. It seemed like a thick sealing washer on the pressue relief valve would do the trick.

The by-pass hole into the oil pump return passage, being drilled from the by-pass cavity itself, is very near the bottom of the hole and the end of the threads. On later models the by-pass hole is drilled from a pilot hole and is located closer to the center of the threads. This seems like a more sensible approach.

I could see why they changed the way they drilled the hole. On the early style it wouldn't take much to cause a problem.

I also wonder if using a later by-pass valve in the early case might cause a problem if the hole wasn't relocated (aligned)...
john


Re: BSA A65 Piston Suggestons? #3803
08/13/05 1:33 am
08/13/05 1:33 am
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Posts: 3,884
Cape Carteret, NC
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Mr Mike Offline
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John,
I put a later model relief assembly (71) in my early (66) cases which had the ball type pressure relief. After testing that I had good oil pressure, I carefully inspected and put the assemblies side by side to insure that the there wasn't a problem with the drilling lining up where it was supposed to. It looked to be just right.
Rich,
Your comments on bore allignment are well founded. I had several cases checked with a dial setup on a Jig boring machine. Two cases were about .001 to .002 out of alignment....not bad They can be corrected to near perfect by align boring the bushing true. Lannis's original case in particular was a whopping .020" off from the left hand bore to the right. If you bored it true, the center distance between the pinion gear and the cam idler was off so the gears bottomed putting the whole works in a bind. Once bolted together, the crank was not running true in the bush and wore it out quickly. You could see the non uniform wear on the old bush. His motor could never been right from day one. So,I guess before we lay out good money for some swap meet cases the bores and deck should be checked....not often possible. "Caveat Emptor" I don't know how common a problem this was, but there are often tell tale signs on these motors that there were quality control issues at Small Heath.
Mr Mike

Re: BSA A65 Piston Suggestons? #3804
08/13/05 12:24 pm
08/13/05 12:24 pm
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Posts: 10,219
Boston, Massachusetts
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John Healy Offline
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Mike:
Ether way you would have good oil pressure, but if the by-pass hole was partially blocked it would restrict the flow of oil out of the by-pass valve into the return side oil line.

In fact, with the output of the by-pass blocked (or partially blocked) you would have higher oil pressure.
It looked to us that if you used the late by-pass valve and a thick sealing washer we found in one gasket kit that you could possibly block or restrict the output of the by-pass valve. I would be interested after making this modification, not that I had oil pressure, but what the final oil pressure really was.

We have a similar problem with Triumphs when a rotary oil pump is fitted. The oil pressure by-pass valve passages (depending on model - there are two: one into the timing cover and another into the crankcase) are not large enough to carry the volume of oil the pump develops. Thus the motor runs with extremely high oil pressure and the pump working to move this oil somewhere adds additional heat to the oil.

Most of the rotary pumps are installed on running motors, and the changes required to make the pump work properly are overlooked. It requires increasing the oil way passages coming from the by-pass valve. Although essential for the pump to work properly, people don't want to start drilling in their case in fear some of the aluminum chips enter the crankcase. On a Triumph, along with other issues, this can raise the pressure to a point where it inverts the oil seal that delivers oil to the crankshaft and total loss of oil pressure.

There is another overlooked problem with grinding the timing side main bearing on BSA and early Triumph 500 wins. When the operator mounts the crankshaft in the cranksahft grinding machine he must center the timing side bearing to within a couple of tenths (.0002"). With the bearing worn he must use the mainshaft which also happens to be where he has to hold the crankshaft. It can be done so the run-out is .0000", but you need an experienced, patient operator.

It isn't hard for an inexperienced operator because of habit used on cars to center on the wear (on a car crankshaft you are grinding all of the main bearing journals so some misalignment is accepted) it is easy for the bearing surface not to be Concentric with the center line of the crankshaft.

Anyone who has worked on Tridents has had first hand experience with re-ground center mains that are not Concentric with the bearing journals on the end of the crank. It is just that it is not as obvious on the twin until you start having problems.
john beerchug


Re: BSA A65 Piston Suggestons? #3805
08/13/05 12:27 pm
08/13/05 12:27 pm
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Posts: 5,103
Stone Creek OH USA
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Rich B Offline
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John

Glad you concur on the oil pressure cavity. Found this several weeks ago helping Lannis and some others via email on A65 oil pressure issues. The early cases do indeed have very little to seal between the high pressure side and dump. Reports of 2 threads (confirmed by a set of cases I have) seems common. That is not enough. The quick and dirty fix seems to be sealant on the existing threads.

I have always installed piston type regulators regardless of vintage. The land in the regulator body does allow for alignment with the drilling.

The piston type regulators have a groove to use an o-ring seal under the hex. This allows deepest seating into the cavity. Any type of external washer seal will increase the chance of high pressure to low pressure leakage.

I have started to measure some of the bits I have laying around and hope to put an article together on this area. Wish I had some Small Heath drawings to compare to, but will just have to use bits.

The early cavities can be improved, just have not decided best way to do it yet. I have a set of very nice A65D cases that have a truly poor cavity I want to use. I suspect, without finding the regulator hole issue, I would have built an A65 that would have gone bang.

The very least that should be done, is add a chamfer to allow the piston type regulator to be used with an o-ring. Seal the threads at the base of the regulator cavity. I have recommended Permatex HyTack, which is what I believe Lannis used also. And BTW, I did this to my 68 Lightning also, even though it doesn't have low oil pressure issues.

The late cases with the regulator dump to the suction side of the return pump seems to have plenty of threads for a seal. It is a vastly improved arrangement.

There are a lot of myths about A65's and why some went bang. I don't believe any of the myths. There was a root cause of the problem. I believe the regulator cavity is the last piece of the puzzle in my mind. The early motors had a list of potential problems that any one could cause it to go bang. Add several together, and you had a rod hanging through the cases. All of those problems are repairable, though the regulator cavity may be a little tougher to resolve.

My project from h*ll is going ot use those cases I noted above. It will have a modified cavity. It will be the test bed for the fix.


Life is too short to drink cheap, bad beer.
Re: BSA A65 Piston Suggestons? #3806
08/14/05 3:27 am
08/14/05 3:27 am
Joined: Jan 2003
Posts: 523
San Diego, CA
Will S. Offline
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Rich B - I've been following your posts on the oil pressure regulators with great interest. I just had an idea while reading the above that maybe it would be possible to bypass the factory set up by blocking the dump hole, plumb up an external regulator, and have it dump back into the oil tank or oil return line?


Will S.
BSAs: '66 & '69 Lightning
Triumphs: '68 TR6R, '68 Bonneville, '73 TR7, '55 6T
'71 Norton Commando

www.britironsd.com
Re: BSA A65 Piston Suggestons? #3807
08/14/05 11:05 am
08/14/05 11:05 am
Joined: Aug 2001
Posts: 3,884
Cape Carteret, NC
M
Mr Mike Offline
BritBike Forum member
Mr Mike  Offline
BritBike Forum member
M

Joined: Aug 2001
Posts: 3,884
Cape Carteret, NC
Will,
I considered exactly what you described on my 66 which has no port for a guage. I had purchased a 1 1/2 inch gauge which would fit between the tach and speedo. McMaster Carr sells pressure reliefs that could be teed in by the gauge and run done the frame to the tank. You would have a truely dry sump then. I scrapped the idea when I saw that I had good pressure, and I made my ball type regulator a permanent test fixture by soldering up the holes and tapping the cap for a gauge. I replaced it with the piston type assembly. You add some risk with the external piping for an oil leak, but it should work. I had good oil pressure with the test setup, but can never be certain that I am still getting it with the new pressure relif. I am leaving that to "faith".
Mr Mike

Re: BSA A65 Piston Suggestons? #3808
08/14/05 12:09 pm
08/14/05 12:09 pm
Joined: Aug 2001
Posts: 5,103
Stone Creek OH USA
R
Rich B Offline
BritBike Forum member
Rich B  Offline
BritBike Forum member
R

Joined: Aug 2001
Posts: 5,103
Stone Creek OH USA
Will

I have an idea to modify the existing regulator cavity and dump directly to the suction side of the return pump. Just like the later engines. Will require some machining and an external line.

Or some modification of the existing cavity to use the o-ring sealed piston type regulator. That is fairly easy to do.

When comparing the pieces side by side, I can see how the piston type has a better chance of preventing bypass. It has more threads at the base, the land to dump is higher on the body. A better situation than the ball type. Plus the piston type doesn't have the inherent leakage at the seat as the ball type does.

If you have a pre o-ring type cases, you need a chamfer at the lead in threads to use the o-ring on the piston type. It will definitley seat the regulator deeper in the engine. This will allow more threads to seal the area between pump oil and dump. Use of a sealant *sparingly* applied to the lowermost threads in the case will increase the seal. A Q-tip with great care is required. Don't want sealant running everywhere!

There still may be better ways with minimal work to seal early cavities. I haven't found it yet.

The late type cases with the dump going to the suction side of the return pump are definitely the way to go. The constant rise & fall of crankcase pressure on early engines will affect the regulator performance as well as the leak path to dump at the threads. The later engines will only see a constant slight vacum on the dump side of the regulator from the pump. A better situation.

But being the Luddite I tend to be, I have every intention of making a set of early (A65D) cases work. They actually have the worst cavity of any set of cases in the garage. And it will not be a mild A65. Think it is the right thing to do. Keep watching.

But I will avoid any bizarre dual fuel expirements with this motor laughing


Life is too short to drink cheap, bad beer.

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