Matchless G12 (all models)
Matchless G12 (all models)
.Developed in 1958specifically to capture the potentially lucrative US market, the last G12 wasproduced in 1966.The Matchless G12 was one of the last motorcycles under the Matchless name andwas also produced as the AJS Model 31 by the same company. Designer by PhilWalker, AMC knew that it had to be a 650 cc (39.7 cu in) but wanted to use asmany parts from the Model 11 as possible. The cylinders could not be bored outfurther so the stroke was lengthened from 72.8 to 79.3 mm (2.87 to 3.12 in),resulting in a capacity of 646 cc (39.4 cu in). This meant developing a newcrankshaft and primary chaincase, which also provided the opportunity to add aLucas alternator. Volume production began in September 1958.Matchless G12 De LuxeIn 1959 the G12 was redesigned and modernised as the De Luxe with a new fullcradle tubular duplex frame and a new cylinder head. Vibration had always been aproblem, so the crankshaft was upgraded to nodular iron. Capable of 100 mph (160km/h) performance, the G12 became popular with the American market.Matchless G12 CSThe Matchless G12 CS (sometimes referred to as the CS X) was an off-road versionof the Matchless G12 with improved ground clearance and a slightly upsweptexhaust and an 8.5:1 compression ratio. It was not a trials competition machinebut instead aimed at the 'desert racer' market in the US. While never as popularas rivals Triumph and BSA 650's in Open Class desert competition, the Matchlesswas powered by a torquey and reliable motor and was suspended with the superiorTeledraulic front fork.Matchless G12 CSRThe Matchless G12 CSR designation officially stood for"Competition/Sprung/Roadster," the same nomenclature used with the G80 and G50models. It is mistakenly referenced as Competition/Sport/Road. It was dubbed theCoffee Shop Racer by its rivals. With its distinctive two-into-one 'siamese'exhaust system and upgraded camshafts the CSR was a high performance motorcyclewith what was, at the time, a high compression ratio of 8.5:1, distinguishing itand the G12 CS from the other G12 models, having a 7.5:1 compression ratio. Thefactory diverted Chief Engineer Jack Williams from AJS 7R development to addressthe problems with leaks and vibration and modify the bikes for racing - with theresult that Ron Langston and Don Chapman won the prestigious Thruxton 500 longdistance endurance race on the AJS Model 31 counterpart to the G12. Encouragedby this victory in 1963 the G12 CSR gained the name Monarch and twincarburetors (the AJS version was renamed the Hurricane).