Hello! I would like to know if this speedo drive 'PATENT APPLIED FOR' was usually fitted on early 1939 M20 with speedo s433m or it isn't original. thanks.

email (option): aleaja79@hotmail.com

Hi Alex..I guess you are referring to the circular drive box fitted on the nearside of the front hub. This was introduced for the 1940 model year. However, you have to remember BSAs model year ran from August to August so '1940' actually ran from Aug.39 - Aug. 40.
I think I am correct in saying all models with a 39 'K' prefix on the frame number would have had the speedo drive gearbox mounted on the front brake plate and all 40 onwards 'W' prefixed models had the later style drive box on the opposite side....Ian

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

I am not sure if that is correct Ian, according to the tank numbers these bikes should be KM20's.

Henk

email (option): ahum@quicknet.nl

C3931142 should be a C5110 number Henk so definitely WM series.

I wasn't absolutely sure on this point Henk..the 'new' drivebox was definitely introduced for 1940 but bikes from that year still shared most specifications with the earlier types, so generally look the same.It is entirely possible though with the wartime situation affecting production and planning things might not always have gone exactly to the plan!.Wasn't the rear light on the bikes in your photo also a 1940 introduction?..or was it 39?..Ian

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

Hello! my M20 is like the photo that Henk shows. It was modified with a plunger rear frame. this year I bought a complete frame XM20 and I am fiting it step by step.
My frame is WM20 18100 ¿could it be changed or could be original?¿which is the source of this bike? ¿what number put in the new XM20?
My M20 have early spares as Baloon deposit, big rear mudguard, inspection timing cover, olds handlebar levers, rubber mounted handlebar yoke assembly, smaller round plate in the front down tube
http://www.birminghamtoberlin.com/id10.html
old footrest, the oil pressure indicator.

I think my bsa could be this model:
http://www.birminghamtoberlin.com/id12.html

Mi documentation is from september 1939.

I have a video in you tube:
http://www.youtube.com/watch?v=M93fnzJN_E8

email (option): aleaja79@hotmail.com

You are right Rik, I think I need new spectacles I thought I saw a 6 digit C number.

Alex, that seems to be an easy job to get that bike all original again. I have lots more pictures of this model M20, let me know if you want more of them.

Henk

email (option): ahum@quicknet.nl

Yes, of course!! thank you very much Henk!
I would like to know more about this model.
Could the engine number get us the correct year of the moto?
In my documentation, the frame number don't appears, only the engine motor and it is 19450.
Thanks.

email (option): aleaja79@hotmail.com

Alex, your frame and engine, whilst being from the same contract, didn't start life together.

Contract C6126 was for 3000 machines numbered WM20 18001 - WM20 21000.

The final machine was delivered on 25/6/1940 so both components are likely to be from May / June 1940.

Your frame's census number would have been C4170314.