Matchless G15

1962 Matchless G15 emblem

Matchless G15 Background & History

The Matchless G15 has an interesting story behind it.  It was AMC’s (Associated Motor Cycles) last foray into the hotly-contested world of vertical twins in the late 1950s.  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 air-cooled bikes.  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.

1962 Matchless G15

The 1962 Matchless G15 was a handsome machine.

Vibration is Always a Problem

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.
1962 Matchless G15

1962 Matchless G15 on display at the Barber Motorsports Museum, Leeds AL.

Matchless gets a Vertical Twin

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 1939 Triumph T100 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 T-100 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.
1962 Matchless G15 engine

The Mk1 (Mark 1) Matchless G15s (1962-63) used this engine which they bored out from a 650 to a 750.  Mk 11 G15s used the 750cc Norton Atlas engine.  This is from a 1962 Matchless G15.

Matchless G15 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.
1962 Matchless G15 engine

1962 Matchless G15 engine, primary side.

Matchless G15 Ups the Ante

But just as the rest of the market caught up with Triumph Triumph’s 500 twin, Triumph upped the ante again by boring and stroking its 500 out to 650cc with the 1950 Triumph 6T Thunderbird, and once again the industry scrambled to keep up. BSA brought out their 650cc A10, and all the rest did the same. Royal Enfield even went as far as offering a larger displacement than Triumph’s 650cc with the 700cc Royal Enfield Crusader twin. Matchless and AJS took until 1958 to come up with their own 650s, the Matchless G12 and the AJS Model 31. Even that number was soon eclipsed when Norton released the 750cc Atlas, the same year that Royal Enfield launched its new 750cc Interceptor. Matchless/AJS needed a 750 twin to parry with the big boys so in 1962, they stretched the already stretched 650 engine from the G12 to to 738cc (calling it a 750) and called it the Matchless G15, which later became known as the Mk I (Mark 1). This was accomplished by boring it from 72mm to 77mm, But this added displacement stressed the engine such that to avoid catastrophic engine failures and endless warranty claims, Matchless sold the G15 in a very mild state of tune. This meant that the new 750cc G15 was had about the same power as the 650cc G12. It didn’t sell well.
1967 Matchless G15

This 1967 Matchless G15 is a Mk II (Mark 2), meaning that it has a 750cc Norton Atlas engine instead of the Matchless engine of the earlier bikes.

Matchless G15 gets Badge Engineered

In 1964 AMC moved all of its various divisions under one roof in Plumstead, England. This put Norton and Matchless together and AMC management was obsessed with mining what it perceived as a rich resource. The1967-69 Norton P11 1967-69 Norton P11 (a750cc Norton Atlas engine in a Matchless G85 frame) was a product of this thinking, and while it never sold in large numbers, it happened to be a great machine. Long before the P11 though, AMC put a Norton engine in a Matchless frame to create a new bike, or rather the second generation of an existing bike. The Matchless G15 Mk I’s engine was a stretched G12 that was fragile at best. From 1964 on, the Matchless G15 Mk II would have the 750cc engine from the Norton Atlas. It was a logical solution. The Norton Atlas was a proven engine that made great power with good durability and it had an excellent reputation. It still didn’t help. The Matchless G15 never sold as well as hoped. Like the G12 that preceded it, The Matchless G15 came in several flavors. The G15CS (Competition Sport) was the off-road/desert racing version and the G15CS-R (Competition Sport, Road) was the roadster. Both were excellent bikes, but by this time, AMC was slipping into insolvency and none of this mattered. AMC closed in 1966, Manganese Bronze Holdings (who already owned Villiers) bought what was left of it, all to get Norton, formed a new company, Norton-Villiers, all to make one bike: the Norton Commando. But that’s another story. Either way, the Matchless G15, all of the Matchless twins and singles were done. Game over.
1967 Matchless G15

One of the very last Matchless's.  1967 Matchless G15 750.

Matchless G15 Motorcycle Books


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