Anji, et al, I spent some time on this issue and tried to figure this out. I am in the midst of sorting many parts that have not seen the light of day for well over a decade. I know I still have one more box of clutch bits and plates somewhere I have not located but I spent some time looking at various BSA parts books for twins and singles, swing arm, plunger and rigid. A-B-C & m series.
My experience is mostly on later Unit twins and more towards Norton & Triumph so, I am a little lost here.
I also read a number of postings here and on BritBike to gain some insights and confused as ever.
But...My project 52-3 A10 Golden Flash (Could be a HOTFLASH if someone was motivated) is missing its clutch so I am not able to measure a known entity. It ALSO appears there is some variations in some of these parts and dimensions based on numerous threads I looked at. Finally, its possible people have swapped around different parts so my point here is:
a 51-52 bike could be anyones guess what is fitted.
So, do you have the factory parts book? I can send you a copy digitally or a link to download one. But based on what the factory said they used, I have ONE basket I found so far that matches the factory description. I have a number of other baskets that clearly are BSA variants and years but I started sorting and cataloging what I have so I needed to do this anyway. (I am knee deep in the Norton and Preunit Triumph dept right now)
What I have found so far is I have a LOT of segmented clutch plates with the replaceable friction bits. You are correct that many are of a cork material. Did not notice anything rubbery but what the hell do I know??? Plus there is more storage areas and inventory to go thru.
I will be doing at some point a Clutch bits ID thread separately,, But hopefully these pictures are helpful in some fashion for you or anyone else sorting this issue out.
The friction and plain steel plates have an OD of Approx 140mm not counting the tabs. For reference, later type Unit single plates while small dont appear to interchange. The later Unit type BSA & Triumph plates are way too large.. But there is a number of different sized plates out there, as well as the tab spacing and sizing differs.
Interestingly I have some plates the same OD (140mm) but instead of male (Proud) tabs they have female notches. I dont know if this is a modified setup or there is some obscure application for these.
As a tangent, I have saved clutch baskets over the years and in a few cases when the notches for the male tabs get too far worn (notched and sloppy) we notched the clutch plates instead and tack welded in hardened steel pins into the basket. This worked well and extended the life of the baskets which are quite expensive to replace. It might be possible to find some asian bike application and ADAPT plates from that as a common sense adaption. Or.. ,more sensibly adapt a modern clutch unit similar to the Pearson-Suzuki mod.
Let me know if I can assist further....
