AA (1937-61)

The AA (M20 & M21) was a motorcycle model produced from 1937 to 1961 with a four-stroke, single cylinder, side valve engine with a capacity of 591cc. In earlier models, the engine had a bore x stroke of 85 x 105 mm, which was changed to 82 x 112 mm after 1938. It was air-cooled and had a compression ratio of 5.0:1. The carburetor used was Amal 76 until 1938, Amal 276 from 1939-1945, and Amal monobloc from 1945 onwards. The motorcycle had a single, chrome exhaust, a magdyno ignition system, and a kick start. It had a max power output of 11 kW / 15 hp @ 4200 rpm, a multi-plate, dry clutch, and a 4-speed transmission with final drive chain. The twin cradle frame had a front suspension of girder up to 1947 and a telefork after 1947, while the rear suspension was spring loaded saddle until 1947 and plunger type after 1947. The front brakes were drum, 7 in up until 1955, and drum, 8 in after 1956, while the rear brakes were drum, 7 in. The motorcycle had steel, laced spokes wheels and 3.25 x 19 in and 3.50 x 19 in front and rear tires, respectively. Its dimensions were 2180 mm / 85.8 m in length, 740 mm / 29.1 in in width, and had a dry weight of 167 kg / 369 lbs. The fuel capacity of the AA (M20 & M21) was 11.4 L / 3 US gal. This information is sourced from Wikipedia.

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Technical specifications:

Make Model: AA (M20 & M21) (M21 specifications recorded. Click here for M20 specifications)

Year: 1937 – 61

Engine: Four stroke, single cylinder, side valve

Capacity: 591 cc / 36.1 in

Bore x Stroke: Up to 1938: 85 x 105 mm After 1938: 82 x 112 mm

Cooling System: Air cooled

Compression Ratio: 5.0:1

Oil Capacity: 2.4 L / 5 US pints

Carburetor: 1937-38: Amal 76, 1939-45: Amal 276, 1945 onward: Amal monobloc

Exhaust: Single, chrome

Induction: Aspirated

Ignition: Magdyno

Battery: 12 V

Starting: Kick

Max Power: 11 kW / 15 hp @ 4200 rpm

Clutch: Multi-plate, dry

Transmission: 4-Speed

Final Drive: Chain

Frame: Twin cradle

Front Suspension: Up to 1947: Girder After 1947: Telefork

Rear Suspension: Up to 1947: None, spring loaded saddle After 1947: Plunger type

Front Brakes: Up to 1955: Drum, 7 in After 1956: Drum, 8 in

Rear Brakes: Drum, 7 in

Wheels: Steel, laced spokes

Front Tyre: 3.25 x 19 in

Rear Tyre: 3.50 x 19 in

Dimensions: Length: 2180 mm / 85.8 m Width: 740 mm / 29.1 in

Dry Weight: 167 kg / 369 lbs

Fuel Capacity: 11.4 L / 3 US gal

Source: Wikipedia