BSA M21     BSA M21


My BSA M21


BSA of the Month in April 2009

I have for many years felt that old motorcycles are very exciting.
Especially the old English motorcycles with their bold sound I find more exciting than the Danish 4cyl Nimbus.

I wanted a big slow engine with great torque, like a 1 cylinder. So the choice fell on the largest single cylinder model BSA ever built. The M21!
I found a reasonably neat and running M21 on Sjślland (DK).
On closer examination I found the M21 was not original, built with a little of this and that from various bikes.

There was no cush drive and the clutch was from a much later model.
After some searching I discovered that what I have, is a BSA M21A, A = Alternators.

The BSA factory had changed the crank and clutch to make room for a 12 volt generator / alternator.

The Alternator model was only produced and sold to the AA roadside service in limited numbers from 1961-63.

It was delivered to military service without badges and knee rubbers.