AJS Model 20 500: review, history, specs

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1955 AJS Model 20.jpg
AJS Model 20
Also called Model 20 500, Model 20 500
Production 1948 - 1959
Class Classic
Successor AJS Model 31
498cc air-cooled twin, four-stroke
Bore / Stroke 66.0mm x 72.8mm
Compression ratio 7.3:1
Top Speed 85 mph (137 km/h)
Horsepower 19.58 HP (14.6 KW) @ 6800RPM
Ignition magneto
Transmission Gear box: 4-speed

Final Drive: chain

Clutch: wet multiplate
Suspension Front: 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
Length 86.22 inches (2190 mm)
Width 27.95 inches (710 mm)
Height 41.34 inches (1050 mm)
Weight 392.42 pounds (178.0 Kg) (dry), 178.0 kg (wet)
Fuel Capacity 3.57 Gallon (13.50 Liters)
Manuals Service Manual

The AJS Model 20 500 is a twin, four-stroke allround motorcycle produced between 1948 and 1959. It could reach a top speed of 85 mph (137 km/h). Claimed horsepower was 19.58 HP (14.6 KW) @ 6800 RPM. The Model 20 was finally discontinued when the 646 cc AJS Model 31 replaced it in the autumn of 1958.

Variants[edit | edit source]

The Model 20B was the model imported into the USA.

Engine[edit | edit source]

The engine was a air cooled twin, four-stroke. A 66.0mm bore x 72.8mm stroke result in a displacement of just 498.0 cubic centimeters. The engine features a 7.0:1 compression ratio.

Drive[edit | edit source]

The bike has a 4-speed transmission. The final drive was via chain. Power was moderated via the wet multi-plate.

Chassis[edit | edit source]

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 telescopic while the rear was equipped with a twin shock. The Model 20 500 is fitted with a 3.57 Gallon (13.50 Liters) fuel tank. The bike weighs just 392.42 pounds (178.0 Kg).

1948 - 1961 AJS Model 20 500[edit | edit source]

1948 - 1961 AJS Model 20 500

The 1948 AJS Model 20 500 has, at its heart, an air-cooled, four-stroke, 498cc, parallel twin cylinder powerplant mated to a four-speed manual transmission. It comes standard with features such as laced wheels, a suspension package composed of a front telescopic fork and dual rear shocks, a solo, sprung seat, wide handlebars, an analogue instrument cluster, a dual exhaust system, full-fenders, a blacked-out frame, and a large, 17-liter (4.5-gallon) fuel tank.