Layshaft End Play Shim On Which End

As I'm now deep into the gearbox on the '74, the whole endplay for a roller bearing issue has now risen to the top.
First, I'm happy to report the Portuguese bronze-caged bearing is intact/not exploded!


So, here's my quandry; if the original gear set worked well with no shims under the kick shaft, why wouldn't we want to shim from the left side (layshaft bearing) rather than under the kickstart shaft? That would place the layshaft in its original position, rather than moving to the left. Shimming under the kickstart shaft appears to have the effect of moving first gear closer to its slide gear, and third gear further away from its slide gear. Or, am I just overthinking this whole thing? The bike shifts so well that I don't want to upset the balance.

My thinking is to shim between the inner race and layshaft input gear (04-0047).

Assuming shims are added to keep the distance between the arrows the same as was pulled from the gear box, no shimming should have to be done under the kickstart shaft.


Thoughts/ideas?

Nathan

I really think the need for shimming came with the superblend Layshaft roller bearing, due to the fact that the shaft would then float the inner within the outer.
With a good ball bearing fitted nicely, no shimming needed. IMO
Look out, other are about to argue.

Nater_Potater said:

As I'm now deep into the gearbox on the '74, the whole endplay for a roller bearing issue has now risen to the top.
First, I'm happy to report the Portuguese bronze-caged bearing is intact/not exploded!

So, here's my quandry; if the original gear set worked well with no shims under the kick shaft, why wouldn't we want to shim from the left side (layshaft bearing) rather than under the kickstart shaft? That would place the layshaft in its original position, rather than moving to the left. Shimming under the kickstart shaft appears to have the effect of moving first gear closer to its slide gear, and third gear further away from its slide gear. Or, am I just overthinking this whole thing? The bike shifts so well that I don't want to upset the balance.

My thinking is to shim between the inner race and layshaft input gear (04-0047).

Assuming shims are added to keep the distance between the arrows the same as was pulled from the gear box, no shimming should have to be done under the kickstart shaft.

Thoughts/ideas?

Nathan

Click to expand...

Shimming is not needed any more with a roller than is is with a ball bearing. The roller bearing has a shoulder that keeps the layshaft from moving any further towards the drive side than it would with a ball bearing.

Shimming is recommended with either bearing to provide adequate first gear engagement. Shim between the kickstart shaft and the inside of the inner cover. Jim

Nate, why is your layshaft sitting on end on a CMM table? Inquiring minds want to know... :mrgreen:

concours said:

Nate, why is your layshaft sitting on end on a CMM table? Inquiring minds want to know... :mrgreen:

Click to expand...

I wanted to know how far it was between the outside face of the bearing and the step of the shaft. It's this dimension that ultimately determines what the end play will be (vs the ID of the case + first gear + kickstart shaft). Assuming all things equal ( :mrgreen: ) I should be able to shim the bearing to match this dimension and have the assembled endplay come out the same as when I first pulled the gearbox apart. And then, I woke up...

Nathan

Hi All.
almost out of this topic; today i have had the gearbox a part for replace the "Portuguese bronze-caged bearing" with a 6203-TB-P63-FAG.
I have found the 4 th layshaft gear mounted with the shamfer side against the 3 th gear and not to the bearing side.
The gearbox worked fine the same.
Ciao.
Piero