Hi,

3 years ago my friend bought an M21 in Belgium for complete restauration.
We think the bike was imported from Indonesie or Indie. There were no papers for registration.
Now he started the restauration and he has some questions:

-The framenumber is: XM213654
The enginenumber is: XM21795
In my opinion the numbers look correct,aren't they?
Can someone tell me what year the bike is made? We think it's after the war?

-The frame has got sidecar lugs. Does it means it is a civil frame?

-And is this correct: The difference between an M20 and an M21 are only the flywheels and the piston. Is the connecting rod different??????

-Is it difficult to find an M21 crankshaft (or flywheels)in England?

Regards from Belgium,

Eric Van Gils

email (option): ericvangils@skynet.be

Yes Eric that number is from after the war. By then I think they all had side car lugs. The only difference between the M20 and M21 is the flywheels which give a longer stroke and the piston. Everything else is the same. Also the carb is slightly bigger on the bore. Ron

email (option): ronpier@talk21.com

Hello,

I too have an M21 that was imported from Indonesia (to Sweden) in the early 90:s. By a strange coincidence I actually met the guy who imported it here and he told me it used to be a "military/army-police bike".

This being my first bike of this kind (previously Triumph and Vespa and some others) I am only beginning to learn things about these bikes but from what I've gathered this far both M20 and 21 have frame numbers starting with 20, only the engine is numbered 21.
Mine has XM20 on the frame and XM21 on the engine.

But hey! Be sure to wait for people on this forum much more knowledgable than me to have their say before taking this to be the whole truth, or even part of the truth.

/simon

That is correct Simon. M21's have M20 stamped as a prefix to the frame number. It's a BSA thing. Likewise BSA C10-C11-C12 all have C10 as a frame prefix.

Ron

email (option): ronpier@talk21.com

Hi,here's a list of all the BSA frame and engine number sequences,hope you find
what you need here
cheers Rick

http://www.britbike.com/bsapitstop/dating/1941-50.html

email (option): richardholt@rocketmail.com

Thanks all for your replies.(especially Rick)
By reinspecting the frame number I saw it was XM20 3654.
According the list the bike was made in 1947.

The engine is XM21....and the cylinderhead is alloy. But the stroke is 94 mm.
So the crankshaft is M20. Is it difficult to find an M21 crankshaft (or flywheels) in England?

Regards from Belgium,
Eric

email (option): ericvangils@skynet.be