Without seeing the oil slinger, it is hard to say why it is only .026" thick. MY guess it is was rubbing on the bearing. Would need to see it to know.
As for shims, my gearbox has none. Shimming it as perfectly as possible using advice on the forum resulted in a disaster as it would not go fully in to third or fourth gear. I took all the shims back out which left the clearances way too big but it shifts perfectly. Also are you using gaskets on the covers? If left out and just using a gasket compound you may not have enough clearance.
Often times poor shifting is caused by the clutch dragging. I am now running a Triumph four spring clutch and it is a big improvement over the BSA one.
I think when you built the gearbox, the mainshaft needs a litte play, sideways. Not much.
And the thickness of the gasket between the housing and the middle cover is very important.
Thanks for your message Bruce, I'm surely gonna try to keep this washer out. I have been told before that it is not always good to keep the rules too strict, so that's what I will do..
I am not ready to give up my single spring clutch becays it is working fine. It can take a while but I will come back with the results.
