The AJS 31 is a motorcycle from the British manufacturer Associated Motor Cycles (AMC).
The AJS 31 is the further development of a four-stroke parallel twin with 500 cm³ that has been built since 1949. To secure sales in the United States, a version drilled to 600 cc appeared in 1956. Because a 650 cc machine was desired, AMC decided to design an engine with a new crankshaft. The motorcycle appeared in model year 1959 under the name AJS 31. Matchless , which is also part of the group , released the model as the G 12.
Model 31 had a compression ratio of 7.5: 1 and an AC system including an ignition distributor.
Model 31 De Luxe
The motorcycle had magneto ignition and manual ignition adjustment as well as a quick-release axle in the rear wheel and was characterized by more ornaments.
Model 31 CS
The machine was intended for off-road sports and was delivered with studded tires. It also had a higher compression and was lighter.
The model corresponded to the 31 CS, but was designed for the road, with correspondingly different tires. The motorcycle reached a top speed of 177 km / h. Strong vibrations, which extended over the entire speed range, were disadvantageous.
Due to the large stroke and heavy pistons, all models tended to break the crankshaft.
|Parameter||Data of the AJS 31 De Luxe|
|Bore × stroke||72 x 79.3 mm|
|power||40 hp at 6000 rpm|
|compression||7.5: 1 (optionally 8.5: 1)|
|Carburetor||an Amal type 389, opening 28.5 mm|
|lubrication||Dry sump lubrication|
|landing gear||lugged single-tube frame with double girders, telescopic fork at the front, strut swing arm at the rear|
|brake||Drum brake front and rear|
|tires||from 3.25 S 19 TT, rear 3.50 S 19 TT|
|Empty weight||195 kg|
|consumption||5 l per 100 km|
|Top speed||155 km / h|
- Oldtimer Markt December 2010 issue, pp. 190–195