AJS Model 31: history, specs, pictures

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AJS Model 31 650
Also called 650 Swift
Production 1957
Class Classic
air-cooled, four-stroke, parallel twin cylinder, OHV, 2 valves per cylinder
Bore / Stroke 71.1mm x 71.1mm
Compression ratio 7.5:1
Horsepower 43.05 HP (32.1 KW) @ 6000RPM
Ignition magneto
Transmission Gear box: 4-speed, manual

Final Drive: chain

Clutch: wet multi-disc, manual
Suspension Front: telescopic fork
Rear: dual shocks
Brakes Front: drum
Rear: drum
Front Tire 3.25 -19
Rear Tire 3.50 -19
Fuel Capacity 4.23 Gallon (16.00 Liters)
Manuals Service Manual

The AJS Model 31 650 Swift was a air-cooled, four-stroke, parallel twin cylinder, OHV, 2 valves per cylinder Classic motorcycle produced by AJS in 1957. Claimed horsepower was 43.05 HP (32.1 KW) @ 6000 RPM.

Engine[edit | edit source]

A 71.1mm bore x 71.1mm stroke result in a displacement of just 646.0 cubic centimeters.

Drive[edit | edit source]

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

Chassis[edit | edit source]

It came with a 3.25 -19 front tire and a 3.50 -19 rear tire. Stopping was achieved via drum in the front and a drum in the rear. The front suspension was a telescopic fork while the rear was equiped with a dual shocks.

1957 - 1966 AJS Model 31 650[edit | edit source]

1957 - 1966 AJS Model 31 650

The 1957 AJS Model 31 650 has, at its heart, an air-cooled, four-stroke, 646cc, parallel twin powerhouse paired to a four-speed manual transmission, and can reach a maximum power output of 43 horsepower at 6000 rpm.

It comes standard with features such as a blacked-out frame, a suspension package composed of a front telescopic fork and dual shocks as a rear suspension, a dual seat, a chromed, dual exhaust system, laced wheels, full fenders, and a dual tone paint scheme.

In Media[edit | edit source]