Hi bastiaan

I run my relatively low compression m20 on a 20tooth

It accelerates even slower than before but delivers in my opinion a cruising speed with less buzzing from the motor & vibes

It does however feel it on hills - not so much a problem where you live

The m21 motor I have in mind for my 1940 bike I will start with a 21 tooth - i think it will take it

Standard gearbox gearing retained

Br

Jo’b

email (option): jonnyob1@googlemail.com

Hi Jo'b (and others),

Thanx again for the advice.

I have found out that it was very specifically mentioned in the contract for the Dutch Army WM21's which sprockets should be fitted to the engine and gearbox (both 21 teeth). I will add a photo I have made from that contract and from the BSA partslist for comparison. The contract is in Dutch, but the gearbox ratio's are easily compared with the 1940 partslist.

Regards,
Bastiaan

https://imgbbb.com/image/p9KsJ


https://imgbbb.com/image/p9wwU

email (option): wdmotorcycles@gmail.com