| MODEL | AJS MODEL 31650 CSR HURRICANE 1957 - 1966 |
| Year | 1957 - 1966 |
| Engine Type | Four stroke, pushrod parallel twin, OHV, 2 valves per cylinder |
| Displacement / Capacity | 646 cc / 39.4 cu in |
| Bore X Stroke | 72 x 79.3 mm |
| Compression Ratio | 7.5 : 1 |
| Cooling System | Air cooled |
| Max Power | 31.4 kW / 43 hp @ 6000 rpm |
| Max Torque | — |
| Ignition | 6 V (12 V after 1964) magneto (Lucas K2F) |
| Induction | Carburettor |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4 speed |
| Clutch | Multi plate (dry, Burman) |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | Single cradle |
| Front Suspension | Hydraulic telescopic fork |
| Rear Suspension | Twin shock absorbers |
| Front Brakes | Drum |
| Rear Brakes | Drum |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | 176 kg / 388 lbs |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 3.25-19 |
| Rear Tyre | 3.50-19 |
| FUEL SYSTEM | |
| Fuel Capacity | 16 Litres / 4.2 US gal |
| Fuel Consumption | — |
| Top Speed | — |
The Model 31 was AJS's 650 cc parallel twin, and the CSR (Competition/Sport/Road) was its sportier road variant, recognisable by a siamese 2-into-1 exhaust and hotter camshafts. It was named Hurricane after success in 1963, and shared its design with the Matchless G12 CSR.
