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1953 BSA M21 in Maroon
1953 BSA M21 in Maroon
1953 BSA M21 in Maroon
1953 BSA M21 in Maroon

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'BSA M21'
Also called M 21
Production 1937 - 1956
Class [[:Category:Classic motorcycles|Classic]] [[Category:Classic motorcycles]]
single cylinder, four-stroke
Bore / Stroke 82.0mm x 112.0mm
Compression ratio 5.0:1
Horsepower 14.62 HP (10.9 KW) @ 4000RPM
Ignition magneto
Transmission Gear box: 4-speed, manual

Final Drive: chain

Clutch: wet multiplate
Suspension Front: hydraulic telescopic
Rear: twin shock
Brakes Front: expanding brake (drum brake)
Rear: expanding brake (drum brake)
Front Tire 3.25-19
Rear Tire 3.25-19
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 396.83 pounds (180.0 Kg) (dry), 167.0 kg (wet)
Fuel Capacity 3.0 Gallon (11.36 Liters)
Manuals Service Manual

The BSA M21 was a single cylinder, four-stroke Classic motorcycle produced by BSA between 1937 and 1956. Claimed horsepower was 14.62 HP (10.9 KW) @ 4000 RPM.


A 82.0mm bore x 112.0mm stroke result in a displacement of just 591.0 cubic centimeters. Fuel was supplied via a sidevalves.


The bike has a 4-speed, manual transmission. Power was moderated via the wet multiplate.


It came with a 3.25-19 front tire and a 3.25-19 rear tire. Stopping was achieved via expanding brake (drum brake) in the front and a expanding brake (drum brake) in the rear. The front suspension was a hydraulic telescopic while the rear was equipped with a twin shock. The M21 was fitted with a 3.0 Gallon (11.36 Liters) fuel tank. The bike weighed just 396.83 pounds (180.0 Kg). The wheelbase was 54.02 inches (1372 mm) long.

1937 - 1961 BSA M21

1937 - 1961 BSA M21 1937 - 1961 BSA M21 1937 - 1961 BSA M21 1937 - 1961 BSA M21

The M21 from British manufacturer BSA sports an air-cooled, four-stroke, 591cc, single cylinder powerplant mated to a four-speed manual transmission that can reach a maximum power output of 15 horsepower at 4200 rpm. Standard fittings for this classic machine include laced wheels, drum brakes in the front and in the rear, a large headlight, a hard-tail rear suspension, a single spring girder fork in the front, a sprung single seat and a chromed exhaust system.

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