Retrospective: Matchless G15/45 750cc (AMC): 1962-1963

[This Retrospective: Matchless G15/45 750cc (AMC): 1962-1963 was originally published in the November 2011 issue of Rider magazine]

The old American adage goes, “There is no substitute for cubic inches.” And in the early ’60s there was definitely a battle for the biggest among the British exporters to the USA. Edward Turner, the man who created the successful vertical twin design, claimed that the ideal power came from that twin when it had 650cc and ran at 6,500 rpm. Maybe, maybe not. The Matchless company decided to exceed that late in 1961.

A bit of history, as always. The brand name was good, denoting a motorcycle without match, beyond compare, or Matchless. The trademarked name was first used on a bicycle in 1891, which evolved into a genuine motorcycle in 1902. A Matchless motorcycle took first place in the single-cylinder class at the Isle of Man in 1907, and won again in 1909 and 1910. In 1931, the beginning of the Great Depression, the company acquired the AJS line, and then in 1938 became Associated Motor Cycles, Ltd. AMC continued manufacturing similar machines with different badges on the gas tank, Matchless or AJS.

U.S. importer Frank Cooper was a businessman, based in Los Angeles, who got the distributorship in the early 1950s and pushed both badges equally. At that time the model range had 350 and 500 singles, in street or competition trim, and a 500 twin. The early Matchboxes were known for their readily identifiable short, stocky, “jampot” shock absorbers—which vanished in 1957 when the company went over to the longer, thinner Girlings.

The G in the G15 model designation came into being in 1935 and meant that this was a sporting mount, as opposed to being a utilitarian plodder. Following World War II vertical twins were all the rage, and Matchless introduced the 500cc G9 in 1948. Followed by the G45 racing version in 1952, with alloy cylinders and heads, hotter cams, higher compression and a splayed head for two Amal GP carburetors.

The G9 was a sophisticated machine, especially in the chassis, with a Teledraulic front fork and a swingarm rear suspension—as opposed to other marques which still had rigid frames, some with plunger rears, and even Triumph’s sprung hub. The engine, with a 66mm bore, 72.8mm stroke, had separate cylinder barrels and heads, and a three-bearing crankshaft—roller bearings at each end, and a plain one at the middle. It made good sense, as this reduced the flexing of the crankshaft. Gear-driven camshafts were at the front and rear of the cylinders, pushing rods up to the valves. Two oil pumps were bolted into the crankcase, in an effort to ensure good lubrication in this dry sump engine—though there were oiling problems in all the twins, mostly due to poor maintenance or abuse. The plugs were sparked by a Lucas magneto, lights lit by a Lucas dynamo. At 6,800 rpm the factory claimed an output of 29 horsepower, which was pretty standard for a half-liter engine of the ’50s.

In 1955 the G9’s cylinders were bored out to 72mm, retaining the 72.3mm stroke, the al­most square engine having a capacity of 592cc. That was close enough to call it a 600, and it became the G11; apparently a G10 model never existed. The G9 barrels had five cooling fins, the G11, six. Some say that this was the smoothest of all the Matchless twins, rated at 33 horses. Two years later the G11 series grew to include the CS scrambler and CSR road sports, with a good-looking two-into-one exhaust system—Siamesed, as the Brits called it. The CSR stood for Competition Sports Road, differentiating it from the off-roadish CS Com­petition Sports model, but the boys liked to refer to it as the Coffee Shop Racer.

But Cooper wanted to give those 650cc Triumph T110s and BSA Super Rockets a run for the customer’s money, and he asked the factory for more. Which he got. When the 1958 catalog came to be viewed, Matchless had no fewer than 17 models. The most popular among the Yanks was the G80 single, which was good for a variety of jobs, including the G80CS scrambler. And the new 650cc G12, with seven fins on the cylinders, as Cooper had gotten his way.

Since the cylinders on the 600 could not take anymore boring out, the engine was stroked to 79.3mm, or 646cc, which required a new crankshaft. The standard model ran a 7.5:1 compression ratio, while the Coffee Shop Racer, clocked at 108 mph, had an 8.5:1 compression ratio with a single Amal Mono­bloc. The standard G12 was now running coil ignition with a new alternator placed at the left end of the crankshaft, whereas the CSR kept the magneto and dynamo.

But something unpleasant was happening in the engine, and vibration had increased, resulting in crankshaft breakage, light bulb destruction and gas-tank fracturing. This was not a problem that affected all the G12s, but enough that the word was out. Thoughtful types pointed out that perhaps the separate cylinders and heads helped to create this vibratory problem, not being as stable as cylinders cast as one piece; same with the heads. And perhaps the stiffness of the crankshaft was actually at odds with the rest of the engine.

Times were troubled, and AMC needed a new distributor; Joe Berliner stepped in with the J.B. Matchless Corp. For 1962 Matchless dropped the 500 twin and the standard G12, leaving the CS and CSR in the 650 class. For the serious road racer a “speedkit” was available, with twin carbs, hotter cams and 10.25:1 pistons.

Berliner also got the new G15/45, as Matchless had bored out the G12 barrels to 77mm, or 738cc—close enough to call it a 750 or 45 cubic inches, and it was advertised in the United States as the Matchless “45.” The cylinders now had eight cooling fins. This was an export-only model, so none made it to the British market. It had the battery and coil ignition like the old 650 standard, a single Amal 389 carb and the 19-inch front wheel, 18 rear, like on the CSR models. The front drum was 7 inches in diameter, but had narrow shoes. With four gallons in the tank, the bike weighed close to 430 pounds. Reports said that the 750 was really not any better than the 650. In ’63 the suggested retail price of the G15 was $1,089, while the G12CSR was $31 more.

This “45” happened to coincide with Norton’s new 745cc Atlas 750, and Berliner was also the Norton importer. In 1962 both Norton and AMC were in dire financial straits, and joined forces. Which may have had something to do with the short life span of AMC’s G15. It was in the catalog for two years, and only 212 got built. The model designation reappeared in 1964 using the Norton engine and other Norton bits.

The end of Matchless was nigh, and the name disappeared in 1969.


  1. the matchbox g15/45 was almost bomb proof .as a crazy 16 year old i crashed that bike many times,only that big headlite got crushed thank GOD for Bob Stark {Indian restoration} who hammered it out for me many times.and with straight pipes i wound the guts out of it everyday,yes the push rods are thin in the center and it never failed ever.and even in the 1970’s Barney Tillman in Montabello ca. had new old stock parts to keep things right.from O.C. to long beach that bike was everyplace everyday like nothing else.ya its against the law but blasting down the wet sand in the afternoon at huntington beach thru the crowd was a hell of a lot of fun.hey it was the 70’s.

  2. Hello Mel, I’ve just read your post about riding your G15/45 along Huntington Beach through the crowd. Made me laugh mate! I’ve got a G12 with a G15/45 engine and it’s loud in an unfamiliar way. Modern bikes sound different and loud also but in a familiar way, if you know what in mean. I’d loved to have seen that. Was there many Brit bikes in California back then? All the best, Jamie.


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