Matchless G9
This 1953 Matchless G9 shows what handsome machines they were. Note the 'Jampot' shocks on the back. These were replaced with Girling units in 1953.
Matchless G9 Background & History
The Matchless G9 was AMC’s (Associated Motor Cycles) first foray into the hotly-contested world of vertical twins in the late 1940s. Life as a motorcycle manufacturer in the 1930s was fairly predictable, everyone had a big OHV single-cylinder bike, or several that were at the heart of their marketing strategy. As World War 2 ended and the world began to return to normal, that was all about to change.
During the 1920s and 30s, motorcycles developed and improved dramatically. One basic engine layout ruled the era: single-cylinder machines. They started out as side-valve (flathead) designs, but soon graduated on to overhead valves (OHV) as performance steadily improved. By the mid-1930s, displacement and power output had nearly reached their practical limits at around 500cc and 25 horsepower. Adding more displacement, or extracting more power by revving the engines faster only led to horrible engine vibrations that were hard on engines and riders alike. Many solutions were attempted but nothing seemed to work.
AMC put a lot of focus on the looks of the Matchless G9. Lots of chrome, a sharp paint job on the chrome tank, even rims trimmed in red.
Vertical Twin is Born
Shortly after Jack Sangster bought Ariel Motorcycles he brought over a promising new designer named Edward Turner, who promptly designed the first Ariel Square Four. When Ariel bought Triumph, Turner was put onto the task of solving the vibration problems the company, and the entire industry, was experiencing. After all Turner had taken a bold approach with the Square Four and it was one of the smoothest bikes in existence.
Like his Square Four design, Turner’s solution took a whole new direction. He split that 500cc of displacement into two parallel cylinders rising and falling together on a 360-degree crankshaft, but firing alternately. The new ‘vertical twin’ as it was dubbed was lighter, made more power, loved to rev, and didn’t have nearly the vibration penalty of the big singles. In 1937 Triumph launched the new engine in a new bike, the 500cc 1938 Triumph 5T Speed Twin. It was an instant hit and changed the entire motorcycle landscape. Suddenly, all the big singles had been outclassed. Most of the British motorcycle industry rushed to bring their own vertical twins to market.
1959 Matchless G9B.
The Race is On!
During this era, and beginning with the Speed Twin, Triumph ruled the roost, always setting the pace of innovation, always leading the way with newer, bigger, faster bikes. As quickly as the rest would catch up, Triumph would launch another bike that left them all in the dust. The Speed Twin did it first in 1938. Then, higher compression, hotter cams and a bigger carburetor were added, boosting horsepower, creating the ‘hot rod-version’ of the new twin, with the 1949 Triumph T110 Tiger. World War 2 broke out in 1939 and all civilian production ended until 1946, but when it did, Triumph was back with a vengeance.
In 1946 Triumph was back with their 500cc Speed Twin and the T100 Tiger. BSA was the first of Triumph’s rivals to hit the market with their own vertical twin, the 1946 BSA A7 Golden Flash. By 1948 Ariel had completed its entry into the fray, the 1948 Ariel KH. Then in 1949 Norton, Royal Enfield and Matchless/AJS all came out with their 500cc vertical twins, and the race was on, to build the best, the fastest, the most powerful, and of course the best-selling vertical twin on the market.
The Matchless G9 engine was as strong as it was good looking, and it had a center main bearing.
Matchless G9 has a Sister!?
Matchless was owned by AMC who also owned AJS and the parent company always treated them as ‘sisters’. When one got a new model the other one did also, virtually identical mechanically, but styled differently and given a different name, or rather a different alphanumeric designation. The new Matchless 500cc vertical twin was dubbed the G9 while the nearly identical AJS bike was called the Model 20. Both were displayed for the first time at the 1948 Earls Court Motorcycle Show (the first after the war), but it took until late summer of 1949 for the bikes to actually show up at dealerships. Both bikes were handsomely styled with lots of chrome and paint. Most of the cycle parts were from the Matchless/AJS parts bin.
Note the Amal Monobloc carburetor, the Lucas magneto behind the cylinders and the dynamo in front. 1955 Matchless G9B.
Matchless G9 gets a Center Main Bearing
This page is dedicated to the Matchless G9, but all the information here also applies to the AJS Model 20, however we will refer only to the Matchless G9 from here on. The G9 launched with a swing arm frame that was years ahead of the rest of the industry. Triumph and BSA wouldn’t get a swing arm until 1953. Another key innovation that set the Matchless G9 apart from every other British vertical twin on the market was a center main bearing. All the others carried their big crankshafts on just two main bearings, just like their big twins. All mounted a heavy flywheel on the center of the crankshaft between the rod journals. At high revs this arrangement was subject to all sorts of negative forces that induced vibration. Engineers call it ‘deflection’, which actually means that the crank was bending as it spun. Very bad on engine parts. Matchless trumped them all with a center main bearing. This provided tremendous support and stability that the others simply didn’t have. And because of this, Matchless was able to cast their cranks out of iron rather than forge them out of steel like everyone else. It was much less costly and worked great. Of all the British vertical twins from this era, the Matchless G9 and AJS Model 20 were by far the smoothest.
Did all this innovation help? Did they outsell, or at least keep pace with the big boys in the game (Triumph and BSA)? Not really. AMCs pair of vertical twins never sold that well, and by the early 1960s AMC and all the brands under their empire (Norton, Matchless, AJS, James and Francis-Barnett) are all struggling just to survive. Norton was the only one making a profit, and the Matchless and AJS singles were the only other bikes that were actually selling fairly well, so the decision was made to shutter every other model and make only Norton twins and Matchless/AJS singles. The Matchless G9 was in production from 1948 through the 1958 model year. It was superseded however by the 650cc Matchless G12 which lasted until 1966.
Matchless G9 Motorcycle Books
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By Brookland Books, Ltd., 172 pagesIllustrated Road Tests, History, Tech Analysis & more. |
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By W C Haycraft, 196 pagesIllustrated, covers every model Matchless built from 1931 thru 1939 with tech, repair & maintenance info. |
More Matchless Motorcycle Pages
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