Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65 bearings yet again...

Thanks for the pic, neat installation which avoids all the welding and drilling other people seem to do.

SR

Not to diverge from the A65 issue but the high wear rate of triple mains is likely from assembly. Assuming the crank mains have been measured and in line, the centre mains are aligned with the end roller and ball bearings with two dowels on each side. If these dowels were a precision fit it would be difficult to mount the cases together since they would have to be dead square to go together. The mains clearance is 0.0005" - 0.002" which is probably the clearance of the dowels in the case. The only way to get close to alignment is to mount a flat plate across the cylinder joint and tighten it along with the case bolts. That only aligns the vertical misalignment. There is nothing to correct the horizontal except the crank.

Yes I think you're right. It's definitely not the best design possible, and easy to screw up. It requires fitting skills rather than assembly skills, which is doomed to fail on an assembly line.
I have my thoughts on thermal expansion as well, the center section may possibly grow faster as it heats up, pushing the mains up and out of center. But that's purely speculation.
I always take care to warm the engine up good before gunning it. As I do with any engine, but some engines are more sensitive, like the A65 for example.

SR

DS ball bearing was used with success by one of Marcs on this forum, now is used by Allan Gill ( if my memory serves me right ) and I'm building another one. My former A65 was used with stock arrangement of bearing for 10 years and perhaps 25000 km with not a hiccup and is used by the new owner in Calgary, who called me last summer to tell me how happy he is with the bike working still like it should.
So even with stock configuration, but regularly maintained these bikes are reliable as regular street bikes.
Only improvements made to this engine were iron oil pump, charging system with solid state reg/rec, oil filter in return line and Boyer ignition. Timing side bush was solid bronze and I believe installed without line boring, but giving good pressure ( no flickering light on idle on hot engine ).
And because of changing its cylinder head to small port version I was able to take it above 7k revs on lower gears more than couple times, closing a tacho ones on third for a second. So yes this bike was ridden quite hard and survived it.
I write all this to say - don't overthink it, I found a Trident much more difficult and fragile bike comparing to old trusty A65.

I'm only having a laugh, same with Stein Roger.

It's just that over the years i've heard so much stuff about how crap the A65 bottom end is and how they all fail.
I raced a standard 650 and 750 converted bog standard bottom end sidecar for 2 years without touching the bottom end
on an A65. In fact i sold the engine to another bloke who raced it too. That was in a sidecar outfit and was used to 8000rpm
regularly. (I won't mention the transmission and other problems though) Incidentally, we used standard gtx 20/50 oil in that motor.
Yes, when i went to a big motor i end fed it etc but the standard setup on a road bike is adequate. (I feel i've proved that!)
It's interesting also that in the 2 years i raced the bike as a morgo triumph, i broke 3 cranks. It made me feel the A65 was
a far stronger motor overall. (and leaked a lot less oil.)
What sort of mileage do you blokes expect from an engine used normally on the road as a classic? I don't expect more than
30k before a rebuild is required. If you cannot put an A65 bottom end together in standard form that will last 30k, i suggest you
either take it to someone who can or buy a triumph. My road A65T is certainly ridden as hard as my T120 is.
Arnstein's hot-rod is a different case, more engineering effort needs to be put into motors like that, and he certainly has done that.

NickL OK, an A65 put together right will stand up to racing use and abuse. At least yours did, but it does come down to skilled assembly doesn't it.
The crank held together better than on a Triumph, well with the bigger big ends and shorter stroke, perhaps it should.

Conclusion after this discussion, other forums and articles, talking to people, is that if I were to build an A65 for myself, I'd let the Chief do the bushing, and consider a ball bearing on the DS.
I'd use a tested and certified oil pump and OPRV and perhaps have the crank dynamically balanced. I'd keep the engine otherwise standard.
An OIF A65 won the Classic Cup in Scandinavia years ago, not by being the fastest, but fast enough and always finish.
When I him asked about "the secret" the guy grinned: "it's completely standard, I'm just in it to have a bit of fun".

I have no desire to super tune or big bore an A65, I'll leave that to others. The likes of Mark Parker and Arnstein have proved what's possible, kudos to them.

Thanks again to all.

SR

NickL, you missed the wink on the end of my comment, I was adding on a twist.

i was serious about the oil dippers .
the a65 was so close to being a viable engine .
being only sixteen when BSA went out of business
they no doubt had there own reasons
for not answering my emails

Question: Why did BSA change the d s ballbearing to a much more expensive set up with a roller bearing? Because of the roller bearings better load capacity or did they want to spend more money on the A65 without reason?

The roller is better but only you and a handful of others need the extra load capacity. The rest are taken to a rally or two in mid summer by riders who never see the north side of 4000 rpm...

SR

I'm doing mine with a roller for both of those reasons. But seriously, I needed a new bearing and the roller just looked so much better.

I recall reading John Healy say something about the switch being due to factory reorganizing and roller bearings being available on the shelf. Something like that.
In other words, I think he implied that it was a practical or economic reason rather than a quality one.
If that is so, they sure went to a lot of trouble remachining the case and changing the crankshaft size to accomodate it.
I'l search for it if John doesn't happen to post on it again.

Hardly, Ive had RHP rollers that are loose on the drive shaft after 3000 miles, the RHP ball bearing I have fitted currently is so far is outlasting that. Not saying that the ball is better than the roller but more likely the bearing not made to suitable specification.

I strongly agree that they didn't change to a roller for no reason, however this came at a point where they were also drilling holes in conrods to fix a different problem. As the A10 had roller bearings fitted albeit of a different size (the ID of the A10 roller is much larger than the A65) Im not sure of the OD of that bearing compared though. They knew the A10's didn't have these problems so likely switched back to what they knew worked.


....Just as assumption, I've known several people who use a ball bearing drive side on a 650 without problems. It probably wouldn't hold up to 750cc+ and probably wouldn't last for those people lugging their motor in a high gear.

The bearing for ball and roller has the same ID/OD and width of the inner and outer race's as each other, changing bearing type isn't a problem in this instance.

True but at the time of the bearing change a thrust washer was added, and changes to the crankcase, timing bush, crankshaft counterweight, to account for the roller end float. There is that problem.

It depends on the full question or the follow up question. If your using a late set of cases then either bearing will fit with no modification.

If your using it on a early set of cases then your story is different. I haven’t dealt with an early set of cases so I’m not qualified to give opinion, but from what I have seen of the TS Bush, the “thrust face” is steel? You would probably have to make an all bronze Bush thus having a bronze thrust face.... Maybe....

But as I say the bearing size wise isn’t a problem.

It is not a good idea to control end float with a roller bearing, the ends of the rollers will be trying to drill themselves into the lip

Information given by INA says that their roller bearings series SL and SL01 are made for to take axial loadings as well as radial.

Ahhh,, you got me there.....................................

(Quote) "Hardly, Ive had RHP rollers that are loose on the drive shaft after 3000 miles, the RHP ball bearing I have fitted currently is so far is outlasting that. Not saying that the ball is better than the roller but more likely the bearing not made to suitable specification."[/quote]



Mr. Gill, are you saying that the rollerbearing came loose on the shaft because it is a roller...and that a ballbearing will not?! To be sure any bearing, roller or ball, not getting loose on a shaft an interference fit is needed, and sometimes a torqued nut, as on A65,

And, as fa as I know the early ballbearing motors did no have any thrust washer. because of the ballbearing it is of course not needed.

A good point is also that they were using the same roller bearing in large numbers in the triumph factory as well.
The simple way would have been to have just converted to a double lipped roller that size, if they thought just the
higher load capacity was needed, they changed several things at that time including the crank dimensions and
case castings. It's likely there were other factors behind it as well.

Hey Stein, as for the skilled assembly of an a65 being so critical, i have no mechanical engineering qualifications at all,
the a65 motor we built in 1991 for the outfit was the first a65 engine i had ever seen inside. I bought a set of brand new
unstamped cases complete with main bush and started there. It just went downhill ever since.....................

That’s not what I said, I didn’t say the bearing id became slack because it’s a roller. What I said was it is probably the quality of the inner cage. What I was pointing out is that the ball bearing is perfectly fine, it probably wouldn’t last in your 800/850 motor and I wouldn’t use a ball bearing on my 823 either. There is also no chance the nut came loose on the end of my crank, but thank you for your suggestion.

I had seen a wrongly pictured item for the TS bush, it was probably off an A10 maybe? It appears to have the same cutaways as the later bushes do, looking at the parts books. Still a ball bearing can walk if there is too much end float. You set the end float of the crank against that Bush face and the ball bearing won’t walk. The oil film is probably just enough in this case, unlike the roller where it will constantly kiss the thrust washer or the lip of the outer cage.

Maybe one of the reasons for going away from the ball race and including a ts thrust was that
when the engine is hot, the tendency for the thrust from the oil pump was pulling the drive side
bearing from it's housing.and allowing the crank to move over to the timing side. The natural
thrust of these engines is definitely toward the worm driven oil pump.

"The natural thrust of these engines is definitely toward the worm driven oil pump" - maybe a case for a spur gear drive oil pump?
Metric roller bearings are available with a separate thrust collar which serves as a second lip on the inner race. Since the single lip on the inner race already provides for the thrust in the drive direction I do not see why the inner race cannot be reversed (lip toward crank) and a thrust collar used on the sprocket side to have the roller bearing take both thrust loads. Solve the whole problem of shimming the crank just as the ball bearing did.
I do not know of any manufacturer that makes them for imperial bearings but it would not be difficult.
One advantage of the Triumph wheeze pump on the camshaft is that it removes any loads on the crank or flex effects on the pump.

My drive side crank shaft wore where the bearing seats, SRM sleeved it back to size. it had a roller, still does.
my crank had run with a slack rotor nut, maybe that did it.