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Matchless G9 Twin

Make Model	Matchless G9
Year	1948 - 58
Engine	Parallel twin cylinder
Capacity	498 cc / 30.4 cub in.
Bore x Stroke	66 x 72.8 mm
Cooling System	Air cooled
Compression Ratio	7.7:1
Lubrication	Dry sump
Engine Oil	Hot: SAE 50 Cold: SAE 30 Extremely Cold: SAE 20
Oil Capacity	2.5 L / 5.3 US pints
Exhaust	Twin, chrome, megaphone silencers
Fuel System	Amal 376/6
Ignition	Magneto, Lucas K2F
Starting	Kick
Battery	Lucas, 6V 12 Ah
Spark Plug	KLG FE80, 14mm thread
Maximum Power	24.3 kW / 33 hp @ 6800 rpm
Transmission	4-Speed
Final Drive	Chain
Gear Ratios	1st 2.67 / 2nd 1.77 / 3rd 1.35 / 4th 1.0:1
Frame	Single top and down pipe, double cradle
Wheelbase	1403 mm / 55.25 in.
Front Suspension	Teledraulic
Rear Suspension	Swingarm, twin shocks and coil springs, oil dampers
Front Brakes	Drum
Rear Brakes	Drum
Wheels	Steel, wire spokes
Front Tyre	3.25 x 19 in.
Rear Tyre	3.50 x 19 in.
Dry Weight	181 kg / 400 lbs
Fuel Capacity	17 L / 4.5 US gal
Top Speed	137 km/h / 85 mph

The Matchless G9 and corresponding AJS Model 20 were launched at the post war Earls Court motorcycle show in late 1948. Initially for export to the US, it was not until the late summer of 1949 that the first examples reached the home market. The styling was modern and the dual seat, megaphone silencers and bright chrome finish justified the name of Super Clubman for the matchless and Spring Twin for the AJS. The rest of the cycle parts were standard AMC, with the engine being housed in a pivoted fork frame with telescopic front forks. The basic design changed little over the course of the next few years, the most significant change being made in 1952 when a new Burman gearbox was adopted.
In 1951, the rear suspension was upgraded to the Jampot unit, derided for its shape in the 28 September issue of the Motor Cycle magazine. In the same year minor changes included a new Lucas horn-push on the handlebar and a medallion badge in place of the previously used transfer. Front fork shuttle damping was also replaced with rod and damper-type.
Progressively developed, the G9's twin-cylinder engine underwent a number of capacity increases, finally being discontinued when the 646cc Matchless G12 (and AJS Model 31 replaced it in the autumn of 1958.