| MODEL | AJS PORCUPINE 1947 - 1954 |
| Year | 1947 - 1954 |
| Engine Type | Parallel-twin, double overhead camshafts, light-alloy cylinders and heads, gear drive to camshafts |
| Displacement / Capacity | 500 cc |
| Bore X Stroke | — |
| Compression Ratio | — |
| Cooling System | — |
| Max Power | About 40 kW / 54 hp @ 7500 rpm (1954) |
| Max Torque | — |
| Ignition | Magneto |
| Induction | Weir-type carburettors with header tank (1954) |
| Start System | — |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4-speed, spur gears, in unit with engine |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | Duplex cradle |
| Front Suspension | AMC Teledraulic telescopic fork |
| Rear Suspension | Pivoting fork |
| Front Brakes | — |
| Rear Brakes | — |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | — |
| Rear Tyre | — |
| FUEL SYSTEM | |
| Fuel Capacity | About 6.5 UK gal (low-slung tank, 1954) |
| Fuel Consumption | — |
| Top Speed | — |
AJS's postwar 500 cc Grand Prix twin was nicknamed Porcupine for the spiked fins on the cylinder heads of the 1947 version. Les Graham won the 1949 world championship on it, but later development, including 45 degree cylinders and pannier tanks on the E95, could not match the Italian fours, and AJS left Grand Prix racing after 1954.
