Can you identify this motorcycle?

I don't know what year or make but the position of the carb and exhaust mean it is in my opinion a 4 stroke side valve. Noel

Regarding Tim Hammond's observation re. tappet chest covers, could it be that the OP's engine was an economy version where black painted pressed tin had been substituted for polished cast ali. ?

Well this thread has caused fun!

Just as Noel says, and Duncan, the position of the exhaust and carb makes it a four stroke and the shallow head says side valve. The poor image makes it impossible to see the side valve chest cover that should sit just below the barrel, presumably it has been painted black.

This first image is of a 1940 BSA M20, side vale single, but the cover for the magneto chain is not quite the right shape.

This second image is of a 1951 BSA C10, side valve single, and the chain cover is the right shape. Obviously this 1951 model has telescopic forks but a BSA marque expert would have to say whether this engine first came out in a rigid frame with girder forks a few years earlier.

Edit: yes, found C10s going back to 1939 link

Previous identification by Micheal and JohnF acknowledged.

Edited By norm norton on 25/01/2022 10:34:10

For my money also it's an early BSA C10. 1939ish or very immediate post war perhaps You can't see the oil tank or the tappet cover because the photo is horribly underexposed (as well as out of focus) so those areas are just black blobs. But you can see a very blurry image/blob of the points "distributor" housing sticking out of the cam timing chest at the 2 o'clock position, which is uniquely C10 AFAIK.

The big 'uns had magnetos up behind the cylinder and the two strokes had flywheel magnetos. The C10 had that unusual points housing.

I believe you can see the blur of the ignition coil above the cylinder head, under the petrol tank, in the OP picture, which matches the photo of the later model ignition coil Norm Norton posted above. Coil ignition was pretty unusual on Brit bikes in 1939, with most using magnetos, so the humble C10 was ahead of its time in one way at least. That's why the other bikes of the day did not have that points housing sticking out like that.

Edited By Hopper on 25/01/2022 11:07:50