Good morning all!

I purchased a S/H inner primary drive case a couple of months ago, a bit cruddy but in great condition. I finally decided to give it a clean and paint but noticed it was quite different to the case that came off the bike. The PCD of the front three holes and foot peg hole location are the main ones.
The original case has the part number 65-7587 (which doesnt appear to be correct either), the replacement has the number 65-7547. The thing is, I cannot seem to find what this case was fitted to originally, any ideas?
Thanks in advance,
Gino.

email (option): gino_kerekes@yahooooo.co.uk

There are multiple versions of these cases from the pre war and post war periods...Post war a C Series bike is the most likely candidate but I don't have a parts list... A picture would help....Ian

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

Hi all,

A photo of the two cases -



poems about passion



Thanks in advance,
Gino.

email (option): gino_kerekes@yahooooo.co.uk

Gino,
The part number you will find on any BSA part is never the same as the part number in the parts book .
IT is the number for the raw part before machining assembly & painting .
Usually it is one or two numbers higher or lower.
Post war B & M cases will interchange however a C or prewar B will not
So if you find a BSA number that is the same as the first 5 numbers , ie 65-754? that is what the chain case fits .

email (option): bsansw1@tpg.com.au

Gino, I can help with one of those numbers. 65-7587 was correct for the sprung frame M20/M21/M33.

It is almost identical to the correct rigid frame WM20 but has a slightly shorter rear chain guard bracket.
I have two original WM20 rear sections that are both stamped 66-7602 (parts book shows 66-7601),
That difference is shown in the comparison photos below - 66-7602 is the first one.




I have one of these 65-7587 parts NOS in olive drab so there must have been some post-war sprung frame machines somewhere.
I haven't had the heart to modify this with a longer chajn guard bracket but that wouldn't be that hard to do.



The closest I can come to your 65-7547 is the the 1937 inner listed as 65-7545 - someone else may have more detailed earlier records.

email (option): rays54@hotmail.com

Thanks for the reply’s all!
I’ve set about repairing the old one now, at least I know it fits!
Gino.

email (option): gino_kerekes@yahoooo.co.uk