| MODEL | MATCHLESS G-12 1959 |
| Year | 1959 |
| Engine Type | Twin, four-stroke |
| Displacement / Capacity | 646 cc / 39.42 cu in |
| Bore X Stroke | — |
| Compression Ratio | — |
| Cooling System | Air |
| Max Power | 25.5 kW / 35 hp @ 6500 rpm |
| Max Torque | — |
| Ignition | — |
| Induction | Amal carburettor |
| Start System | — |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | — |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Telescopic |
| Rear Suspension | Swingarm with coil-over shocks |
| Front Brakes | Drum (expanding) |
| Rear Brakes | Drum (expanding) |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | — |
| Wheelbase | — |
| Ground Clearance | — |
| Dry Weight | 180 kg / 396.8 lb |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | — |
| Rear Tyre | — |
| FUEL SYSTEM | |
| Fuel Capacity | — |
| Fuel Consumption | — |
| Top Speed | — |
The G-12 was the large parallel-twin road model in the Matchless range from the late 1950s into the mid 1960s, a sporty 650 with an Amal carburettor, telescopic forks and a swingarm frame with twin shocks. The database credits Phil Walker as designer. The page notes it was also sold as the AJS 31 by the same company.
