The Birmingham Small Arms company did not produce motorcycles until the 1920's, although they had been supplying motorcycle parts to many other manufacturers before then. In the 20's and 30's they produced a wide range of motorcycles, including 770cc and 998cc V-twins, 249cc and 349cc singles, and even a 174cc two-stroke.
Although BSA never competed officially in races, their 348cc Gold Star, introduced in 1938 and produced on and off until the company ceased production in 1971, was wildly popular amongst racers because if its simplicity, speed, and reliability.