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1957 Matchless G11

Matchless entered the vertical twin race in 1949 with the 500cc G9 and its sister-bike, the AJS Model 20. Both shared the same basic engine, which was unique among British vertical twins because it had a center main bearing. This made for a much stronger, smoother engine. In late 1955 they completed work on an enlarged version, now with 593cc (600) resulting from a near-square 72mm X 72.8mm bore and stroke. The resulting motorcycles were the Matchless G11 and the AJS Model 30. They were meant to be a stopgap between the 500cc G9 and the yet-to-be-introduced 650cc G12. Hence the Matchless G11 and AJS Model 30 were only produced from 1955 through 1959, overlapping production of the new 650 G12 which launched in 1958.

1957 Matchless G11 SPECIFICATIONS

Model designation

Engine type


Bore & Stroke

Compression ratio

Lubrication system

Oil capacity

Fuel system

Ignition system


Engine output

Primary drive



Gearbox ratios

Final drive

Frame type

Suspension, front

Suspension, rear

Brake, front

Brake, rear

Tire, front

Tire, rear


Fuel capacity


1957 Matchless G11

Air-cooled OHV vertical twin

593cc / 36.2 ci

72.0mm X 72.8mm


Dry sump

5.3 US pints / 2.5L

1- Amal 376 or 378

Lucas K2F magneto

Lucas 6-volt, 12 amp-hours

33 hp @ 6800 rpm

Chain, on left side

Multi-plate, wet

4-speed constant mesh, right-foot shift

1st 2.67 / 2nd 1.77 / 3rd 1.35 / 4th 1.01

Chain, on left side

Single top & down tube, double cradle

“Teledraulic” forks w/hydraulic damping

Swing arm w/2 shocks (dampers)

8-inch SLS drum

7-inch SLS drum

3.25″ X 19″

3.50″ X 19″

55.25″ / 1403mm

4.5 US gal / 17L

400 lbs / 181 kg