[1] The BSA C11 was a pre-unit single-cylinder developed before the Second World War from the sidevalve C10.

Fitted with overhead valves and displacing 249cc, the C11 was launched in 1939 and continued to be developed into the 1950s.

Modifications for war use included a rear carrier over the mudguard, an additional air filter on the fuel tank and a mag dyno in place of the coil.

The C11G also had improved front brakes and became popular as a post war commuter motorcycle.

[1] From 1956 the C11 was replaced with the BSA C12 which had the same 249cc overhead valve engine in a modern frame with good suspension, more efficient brakes and a more comfortable seat.