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1939 B.S.A. M20

BSA's 400cc model M20 was introduced in 1938. With World War II imminent, the British government quickly ordered 8,000 M20's for military use. Heavy and cumbersome with low ground clearance, it wasn't the ideal battlefield machine, but above all it was supremely reliable and easy to build. Over 126,000 were built for the Allied forces and remained as the primary military motorcycle for 20 years. Sometimes the handgrips were made out of canvas when rubber was in very short supply.

1944[edit | edit source]

In Media[edit | edit source]

One was used in raiders of the lost ark by a villain

1939 B.S.A. M20.jpg
Production 1940
Class Classic
air-cooled, four-stroke, single cylinder, side valve
Bore / Stroke 81.3mm x 81.3mm
Compression ratio 4.9:1
Horsepower 13.01 HP (9.7 KW) @ 4200RPM
Transmission Gear box: 4-speed, manual

Final Drive: chain

Clutch: dry, multi-plate
Suspension Front: parallelogram fork
Rear: hard-tail, sprung seat
Brakes Front: drum
Rear: drum
Front Tire 3.25 x 19
Rear Tire 3.50 x 19
Wheelbase 54.02 inches (1372 mm)
Length 85.79 inches (2179 mm)
Width 29.09 inches (739 mm)
Seat Height 28.5 inches (724 mm)
Weight 167.0 kg (wet)
Manuals Service Manual

The BSA M20 was a air-cooled, four-stroke, single cylinder, side valve Classic motorcycle produced by BSA in 1940. Claimed horsepower was 13.01 HP (9.7 KW) @ 4200 RPM.

Engine[edit | edit source]

A 81.3mm bore x 81.3mm stroke result in a displacement of just 496.0 cubic centimeters.

Drive[edit | edit source]

The bike has a 4-speed, manual transmission. Power was moderated via the dry, multi-plate.

Chassis[edit | edit source]

It came with a 3.25 x 19 front tire and a 3.50 x 19 rear tire. Stopping was achieved via drum in the front and a drum in the rear. The front suspension was a parallelogram fork while the rear was equipped with a hard-tail, sprung seat. The wheelbase was 54.02 inches (1372 mm) long.

1940 - 1956 BSA M20[edit | edit source]

1940 - 1956 BSA M20 1940 - 1956 BSA M20 1940 - 1956 BSA M20 1940 - 1956 BSA M20

The BSA M20 was one of the most successful models produced by the British brand, being used also by the British Army throughout World War II. It had, at its heart, an air-cooled, four-stroke, 496cc, single cylinder powerplant mated to a four-speed manual transmission and can produce a claimed 13 horsepower at 4200 rpm. Standard fittings for this machine included a single, sprung seat, a hard-tail rear suspension, a parallelogram front fork, a large headlight, a steel exhaust system, pull-back handlebars, laced wheels and analogue instrumentation dials.

In Media[edit | edit source]