Does any one know the make and model of the gearbox fitted to my 1937 B21, as I can find no ID on it. The gearbox is a 4 speed hand change, also, any ideas of where I might get a schematic drawing.
Thanks Kevin
The gearbox should be a BSA one.
There's a handbook and parts book for this model in the members area (if you're a member - if not, why not join?) ... extract showing the gearbox inners attached
As far as I know, unlike other manufacturers, Pre War BSA's never specified a gearbox model number. As Jabba states, they made their own gearboxes, so the make of gearbox is BSA. They never had model numbers. If it's of interest, the Part Number for the gearbox casing is 65-3006 and was fitted to the B20,21,22,23,24,25 and 26.
There may be a casting number on the bottom of the gearbox for identification, but I don't know what it is.
You may find 'BIRMAL' (Birmingham Aluminium Casting Company) cast into the underside, so I assume they made the casing for BSA.