I recently bought a 1950 BSA B31.Bought at auction and it seems ok,although the timing appears to habe been done in the fully retarded position. Its fitted with an 18 inch rear wheel and a 4.00 x 18 tyre.Am i correct in thinking both wheels should be 19 inch.
Hi,
The Roy Bacon singles restoration says B31, 1946-59, front 3.25 x 19", rear 3.25 x 19".
Rim part numbers for a 1950, front 65-5543 and rear 67-6263 swinging arm, or front 65-5543 rear 65-6005 for plunger.
Best wishes...