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

[2] The C11 frame was improved in 1951 when BSA added plunger rear suspension.

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.