Matchless G12
Encyclopedia
The Matchless G12 is a British motorcycle
made by Associated Motorcycles at the former Matchless
works in Plumstead
, London
. Developed in 1958 specifically to capture the potentially lucrative US market, the last G12 was produced in 1966.
by the same company.Designer by Phil Walker, AMC knew that it had to be a 650 cc but wanted to use as many cycle parts from the Model 11 as possible. The cylinders could not be bored out further so the stroke was lengthened from 72.8 to 79.3 mm (2.9 to 3.1 in), resulting in a capacity of 646 cc. This meant developing a new crankshaft and primary chaincase, which also provided the opportunity to add a Lucas alternator. Volume production began in September 1958.
development to address the problems and modify the bikes for racing - with the result that Ron Langston and Don Chapman won the prestigious Thruxton 500
long distance endurance race on the AJS version of the G12. Encouraged by this victory in 1963 the G12 CSR gained the name Monarch and twin carburettors (the AJS version was renamed the Hurricane).
750 cc engine replaced the trouble prone AMC unit. In 1962 and 1963, AMC had produced a limited run of 212 touring motorcycles of 738cc displacement using an enlarged version of the G12 AMC-designed engine, but these bikes - which were given the model designation "G15/45" - proved even less reliable than the 650 cc version when ridden hard. So AMC's original plans to develop a 750 cc desert racer version were abandoned. If successful, this could have saved the company as there was a huge unmet demand in the US for powerful desert racers to compete in endurance events. By this time the company were in financial trouble and production ended in 1966.
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
made by Associated Motorcycles at the former Matchless
Matchless
Matchless is one of the oldest marques of British motorcycles, manufactured in Plumstead, London, between 1899 and 1966. A wide range of models was produced under the Matchless name, ranging from small two-strokes to 750 cc four-stroke twins...
works in Plumstead
Plumstead
Plumstead is a district of south London, England, located in the London Borough of Greenwich. Plumstead is a multi cultural area with large Asian and Afro-Caribbean communities, in similarity to local areas such as Woolwich and Thamesmead...
, London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
. Developed in 1958 specifically to capture the potentially lucrative US market, the last G12 was produced in 1966.
Matchless G12
The Matchless G12 was one of the last motorcycles under the Matchless name and was also produced as the AJS Model 31AJS Model 31
The AJS Model 31 was a British motorcycle made by Associated Motorcycles at the former Matchless works in Plumstead, London. Developed in 1958 specifically to capture the potentially lucrative US market, the last Model 31 was produced in 1966.-AJS Model 31:...
by the same company.Designer by Phil Walker, AMC knew that it had to be a 650 cc but wanted to use as many cycle parts from the Model 11 as possible. The cylinders could not be bored out further so the stroke was lengthened from 72.8 to 79.3 mm (2.9 to 3.1 in), resulting in a capacity of 646 cc. This meant developing a new crankshaft and primary chaincase, which also provided the opportunity to add a Lucas alternator. Volume production began in September 1958.
Matchless G12 De Luxe
In 1959 the G12 was redesigned and modernised as the De Luxe with a new full cradle tubular duplex frame and a new cylinder head. Vibration had always been a problem, so the crankshaft was upgraded to nodular iron. (My 1960 G12CSR did not have a nodular crankshaft and broke to prove it, the factory did fit a replacement nodular iron crankshaft free of charge; if you tap the crankshaft and it rings it is not nodular iron, if it just goes 'thud' it is). Capable of 100 mph (160.9 km/h) performance, the G12 became popular with the American market.Matchless G12 CS
The Matchless G12 CS (sometimes referred to as the CS X) was an off-road version of the Matchless G12 with improved ground clearance and a slightly upswept exhaust. It was not a trials competition machine but instead aimed at the 'desert racer' market in the US.Matchless G12 CSR
The Matchless G12 CSR designation officially stood for Competition / Sport / Road but it was dubbed the Coffee Shop Racer by its rivals. With its distinctive 2 into 1 'siamese' exhaust system and upgraded camshafts the CSR was a high performance motorcycle but still prone to leaks and vibration. The factory diverted Chief Engineer Jack Williams from AJS 7RAJS 7R
The AJS 7R was a 350 cc racing motorcycle built from 1948 to 1963 by Associated Motor Cycles, also known as the ‘Boy Racer’, first won victories for the factory, and then went on to win races for privateers when made generally available from 1954....
development to address the problems and modify the bikes for racing - with the result that Ron Langston and Don Chapman won the prestigious Thruxton 500
Thruxton 500
The Thruxton 500 is a 500 mile motorcycle endurance race held at Thruxton Circuit, near Andover in Hampshire, United Kingdom, which is the fastest racetrack in the country...
long distance endurance race on the AJS version of the G12. Encouraged by this victory in 1963 the G12 CSR gained the name Monarch and twin carburettors (the AJS version was renamed the Hurricane).
Matchless G15/45
In 1964 the CSR gained Norton brakes and forks, and the following year a Norton AtlasNorton Atlas
The Norton Atlas was a Norton motorcycle made by between 1962 and 1968, until it was replaced by the Norton Commando.-Development:The Mark 1 Atlas was launched as the 750SS in the early 1960s. Designer Bert Hopwood’s 497cc Dominator engine was bored and stroked out to 745cc, via 600cc and then...
750 cc engine replaced the trouble prone AMC unit. In 1962 and 1963, AMC had produced a limited run of 212 touring motorcycles of 738cc displacement using an enlarged version of the G12 AMC-designed engine, but these bikes - which were given the model designation "G15/45" - proved even less reliable than the 650 cc version when ridden hard. So AMC's original plans to develop a 750 cc desert racer version were abandoned. If successful, this could have saved the company as there was a huge unmet demand in the US for powerful desert racers to compete in endurance events. By this time the company were in financial trouble and production ended in 1966.