SO now I have the correct chain case, I realize that my WM20 has the wrong gearbox installed. I think its off an A10 or something similar...

Anyhow, time to get me another transmission. A bit hard here in the US, but was wondering whether any other tranmissions will fit? What about a C10? Any advice gladly accepted!

Cas

email (option): cas.vanderwoude@gmail.com

Hi Cas...If you have a rigid/girder fork M20 there are basically two gearboxes that will fit straight in without modification...

The correct one and the later version of it, that was fitted to rigid/telefork and plunger M20s/21s/B31s and B33s...

There is more than one type of C series gearbox and none of them are a straight fit. The only one that might be considered would require modifications to the gearbox itself and to the gearbox mounting plates (at least) if the chain cases were to be retained...

You might have a 4 speed C Series box fitted at the moment (as opposed to A10) and that may be the reason why the primary cases weren't fitted...

The 4 speed C Series box looks like an A10 box (it is a plunger A10 box with a modified main case) but its distinguishing feature is that it has two mountings underneath, similar to the M20 box...

However, it is considerably taller than the M20 box and that is why the original cases won't fit... Ian

email (option): ian@wright52.plus.com

thanks for the advice Ian. A B31, B33 box may be easier to find over here and it expands my search window. Rather frustrating but thats how it goes with older motorcycles sometimes - gotta sort out 70 years of someone else's handiwork...

email (option): cas.vanderwoude@gmail.com