Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65 End float with needle roller/ball conversion

Hi

+1 on that fix.

John

With respect to the timing side needle roller only bearing (i.e. no ball bearings) is the timing side thrust washer required? I presume so.

JJC

Yes, you still have to keep the crank from running against the case (which is what the timing side ball/needle or drive side ball would do).

https://swf-ignitionsystems.nl/wp-content/uploads/2021/08/P1050079.jpg

https://swf-ignitionsystems.nl/wp-content/uploads/2021/08/P1050081.jpg

https://swf-ignitionsystems.nl/wp-content/uploads/2021/08/BSA-Axiaal-lager-20170108-01641-1.jpg

works fine

JCC with a straight needle roller, a bearing outside the alternator locates it. That's what I do. It needs setting up central when putting it together while you can still see either the T/side or rods in the bores. Spacers position the crank. Other people may use a thrust washer but the bearing plate works for me as it also limits crank flex and chain misalignment, where a bit of flexing and the wide triplex can knock side plates off. So it's extra control to add to one behind the clutch.

You can see the G/box mainshaft flex without its support by feeling the primary and putting your foot on the rear chain and pushing. Big Laverdas use the same chain, the chain is strong but can come undone on a hot BSA pulling the sprocket out of line. Possibly some cheaper ones are more fragile or not well riveted. Regina seem good and originals.

Just looked, neat setup Lemans. No side load on the bearing.

That's a very good point Mark, we found when racing that a duplex primary
chain lasted about twice as long as a triplex. Due to the flex on the crank,
it would pull the chain out of shape in a strange way. BUT that was on an
outfit with a 900 engine and a lunatic riding it, i don't think it would be so
much of a problem on the road.

So is the duplex just the same size. Your bigger front sprocket changes that length a bit, but can you just run them on the std sprockets on the inner runs? I can see as you go wider the more critical alignment would be. You would think it would be 33% stronger but not like it is. I've seen them come apart and punch through the case.

I used an alloy basket for years, it's ok but breathing through that chaincase it was putting fine alloy and anodizing in the engine oil. It would be fine in the Firebird not breathing through that case. I couldn't tell a difference with the alloy basket.

I wonder if an outside support on a Triumph crank would preserve them, it wouldn't be flexing as much. I read the Triumph guys machined alternator rotors so they didn't chew up stators, a bearing could stop that, and maybe the drive is what snaps them.

I'm going to get technical. If you put a length of wood across two bricks with overhang one end and push in the middle it flexes down as the end of the overhang goes up, but if that overhang is held in line it reduces the flex in the middle as well. And pull on that unsupported overhang could add flex.

You could modify a BSA 68-729 stator mount to go inside a Triumph (! that would be a real mongrel) to stiffen the stator support. There is about 28mm from the stator holes in the Triumph case to the cover joint and 22mm from the joint to the 68-729 stator seat. With the stator in the primary cover there is about 15mm from the back of the stator to the cover joint so the stator mount has to be shortened.
I would make a custom mount, since the outrigger bearing mount should locate on the rim of the stator laminations rather than the through bolts which have clearance.
Aren't we all lunatics for riding these old crates?

Mark, the chain is/was the same pitch etc, just duplex 82 links rather than triplex.
I did have an outrigger on my outfit at one stage but when i machined the case
for the 33 tooth sprocket. i couldn't fit it back on. This is an early set of cases so
there are just 3 stud holes into which we've made up an outrigger setup for the
32t sprocket. We could run a triplex chain on here if we replaced the sprocket
but getting one may be awkward.

I like your technical analysis of the crank but you must remember that stiffening
things up too much makes them break like carrots. Shafts must flex around the
bearing areas if they are just made from EN16 etc. Maybe EN40B nitriding steel
can be totally rigid but that's not the case with this old gear.

Thanks, indeed no side load. and the solution is identical to the BSA-layout. this is the expensive one, used a brass-plate as a bearing material. Recently I modified a crankshaft to the same needle-roller and used an aluminium plate. The side load isn't a load at all and most japanese camshafts run directly on the cylinderhead-aluminium.

lemans, the brass plate takes the thrust to the timing side, how did you take the thrust to the drive side, a washer outside the needle bearing?

no it is just the std BSA setup. so the drive-side rollerbearing has the shimms for axial-clearance and the timing side thrust washer (brass or alu plate) positions the crankshaft in the middle of the cylinder bores.

as you can see from the second picture I've left a 3mm ridge (in the timingside casing) to prevent the needleroller from moving out. so the crankshaft is free to move in axial direction, limited by plate and shims. just like BSA did it with the timing-side bush

and the needleroller cage can't move outwards (ridge) and can't move inwards, thrustwasher and crankshaft
but there's no side load on the needles/cage, so the bearing has no reason to move. and a light interference does help.

I was reading about Nigel Rollason's A65 outfit. He said they were getting over 90hp. Running a 3 bearing crank and a 3 bearing G/box main shaft. They put a bearing where the alternator would go which also controlled end float, As with my set up except mine is outside the alternator. I'm rebuilding one at the moment, a 90degree 744 that the bottom end has not been apart since about 1998 when it was built. It was running fine with good oil pressure but the alloy rods though looking in good condition are getting old and without a remote filter we were wondering about sludge in the crank.

Before I had a plain spacer between bearing and threads on the crank and the threads under it were a bit worn. So I made this spacer to use a Norton spigot nut under the bearing. So it slides into the bearing so the hex section acts as a washer between it and the alternator rotor. Because a loose washer in there is very hard to assemble. Then the spigot nut threads under it.



Nigel said with these extra bearings primary chains gave no problem at all. As they would stay aligned. As late as 1986 the Hogg brothers on an A65 were taking wins in modern racing, causing headaches for Yamaha TZ700-750 outfits and 900 Z1s.

The outfits really tested drive lines and they showed just how potent A65s could be.

Hi Mark,I took a slightly different approach. I made the spacer with a step pocket. The pocket is deep enough so the end of the nut does not bottom on it and the spacer locates on the stud. The bearing is clamped between the hut flange and spacer.