1948 BSA M21 600cc Motorcycle

The Birmingham Small Arms Company began producing motorcycles in 1910 and went on to become one of the world's largest motorcycle manufacturers.  Chief Designer Vale Page reworked the existing range in 1936 and the following year saw the introduction of the M20 (500cc) and M21 (600cc) side-valve singles, the latter essentially a long stroke version of the M20 rated at 13 horsepower.  With its solid frame, torquey 600cc motor and heavier flywheel, the M21 was ideally suited for sidecar use and sold well in the years leading up to the war.  With the outbreak of hostilities, the War Department had a virtual monopoly on BSA’s motorcycle production, including the M21, but it was the smaller M20 that became the mainstay of the British Army, Royal Navy and Royal Air Force.  Production of the M21 resumed in 1946 virtually unchanged from its pre-war form, but a number of developments took place in 1948, including telescopic front forks and a fresh front down-tube frame design, followed by a revised gearbox in 1949.  The M21 ultimately remained in production until 1963, by which time the largely antiquated design was a relic of a bygone era.