B.D. 500

The BD 500 was a highly advanced four-stroke, single-cylinder, unit-construction motorcycle designed in 1926 by Jaroslav F Koch for the Czech company, Breitfeld-Danek of Prague. The 500cc engine had double-overhead camshafts, a bore of 84mm and a 90mm stroke and was rated at 15hp at 4,400rpm. 

Mounted in a robust and up-to-date chassis with thoughtful features such as a magnesium chain guard, it made for an absolutely superb machine that had great success in most branches of motorcycle sport, despite being produced in the relatively small numbers associated with such high-end engines.

Although Breitfeld-Danek was taken over by CKD in 1927 and then by Praga in 1929 (one of Czechoslovakia’s leading car makers), the BD 500 retained its identity and continued to be made until 1933.