Ariel Owners Motorcycle Club

My VH engine has always been mechanically noisy and harsh so I have finally had the engine apart to investigate. I found nothing unusual until I removed the crankshaft and found it had three roller bearings rather than the outer driveside bearing being a deep groove ball bearing.
I was under the impression the ball bearing limited the crank end float. The timing side bearing was a lipped roller and I guess this restricted the endfloat on the crank. The two driveside rollers were in good condition but the timing side bearing was in a very poor state, possibly caused by the rollers hammering on the lip.

Any thoughts? - Pete

Not good to use the lips on rollers for end thrust they are not designed to do that, whereas ball races are. Apparently the lips are intended to act as a sort of safety net.

The datum for crankshaft end float on a 1936-59 single is the ball bearing on the drive side. I am surprised that the roller used in place of it doesn't show damage. Has the inside of the timing pinion worn away the timing case?

The Huntmaster (and BSA A10 for that matter) have a bush for the the timing side main and a lipped roller on the drive side. There's nothing 'positive' as such to locate the crankshaft and the lipped rollers don't seem mind about dealing with end-float.

SG

There's nothing 'positive' as such to locate the crankshaft and the lipped rollers don't seem mind about dealing with end-float

Simon, I seem to remember that the end-float on BSA twins is controlled by the timing side bush which is pulled onto the crankshaft by the timing pinion. The actual float is set by adding shims between the crankshaft and bush flange sufficient to keep the rollers on the drive side clear of the lip.

I might be wrong - it been 50 years since I dismantled a BSA twin.

Pete

I am surprised that the roller used in place of it doesn't show damage. Has the inside of the timing pinion worn away the timing case?

Paul,

Both the outer bearings are lipped and it appears to have been shimmed so as to get the desired end-float between the two lips. Hence the timing pinion is held clear of the crankcase which is undamaged. The drive-side bearing does show some contact with the rollers on the lip however the timing-side bearing seems to have got the worst of the deal.

Pete

Pete.Silson wrote: ↑Sat Mar 09, 2024 10:43 pm

There's nothing 'positive' as such to locate the crankshaft and the lipped rollers don't seem mind about dealing with end-float

Simon, I seem to remember that the end-float on BSA twins is controlled by the timing side bush which is pulled onto the crankshaft by the timing pinion. The actual float is set by adding shims between the crankshaft and bush flange sufficient to keep the rollers on the drive side clear of the lip.

I might be wrong - it been 50 years since I dismantled a BSA twin.

Pete

If I recall correctly, you put the shims under the inner race of the drive side bearing, so the shims can't move. The crank floats between the bush flange and the lip on the drive side main.

As Paul says the outer race (BALL bearing) kept in place by a circlip in the alloy does the locating of the crankshaft using the force of the spring in the cush drive. Nev

Pete.Silson wrote: ↑Sat Mar 09, 2024 10:43 pm ...I might be wrong - it been 50 years since I dismantled a BSA twin.
Pete

I've just spent a couple of days measuring and shimming a Huntmaster bottom end.

As has been noted the shims go between the roller bearing inner and the crank web, the timing pinion gets tightened against the crank journal on the other side.

There is no positive location of the crank, it's free to float between the timing side bush and the (outer race) lip of the drive-side roller bearing, which doesn't seem to have any problem dealing with any stresses from this type of setup.

SG

Duplicated and hopefully deleted this time Nev