Hi everyone,
My 1939 M20 gearbox shifts very poorly since the day I own it, twenty years ago. I took it apart several times, on Ian's advice (thank you) I checked all dimension of clutch- and box parts and placed new parts if necessary. Most parts already looked very good, except part 24-4235, the oil flinger washer Ø1,82"x Ø0,752"x 0,026". It is severely damaged and bend and according to the books it should be 0,04" thick instead of 0,026. It is #91 on the exploded view.
Other than this ring, there were no other rings/shims present, of course apart from the one which fits in the casing close to the bearing.
What I would like to ask is if anyone knows what could be the reason of the fact that ring #91 on the picture is so severely damaged.
Is this maybe the cause of the malfunctioning of the gearbox and has once experienced this?
And the main question - request; I have tried a lot but what I cannot find in all my books and manuals is how to exactly shim all the shafts of the gearbox. Does anyone have a manual other than that in the standard manual, or mr Genthner's very valuable document 'BSA M type gearbox'.
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.
