Back in 1952 it had become part of Associated Motor Cycles, which produced the Matchless and AJS marques, but the entities remained entirely separate. ![]() In 1963 major changes had been made in the Norton company. The Brits, disingenuously, gave them both 49. When Berliner gave test bikes to the magazines, he “estimated” the Atlas horsepower to be around 56, while he advertised the 650 Manxman as having 52 at 6,800 rpm. The biggest differences between the 650 Manxman-a name insisted on by Berliner, although Norton had never raced a twin at the Isle of Man-and the Atlas was that the latter had but one Amal Monobloc carburetor and a modest 7.6:1 compression ratio, while the Manxman had two carbs and an 8.9:1 ratio. These were all relatively long-stroke engines, the theory being that this would help keep the revs down, as high rpm was where all those vibratory problems really came about. Then came the 750 Atlas, based directly on the 650, with the bore enlarged to 73mm and the stroke retaining its 89mm. In 1960 the first 650 appeared, which was really an all-new engine from the crankcases on up, that kept the 68mm bore and increased the stroke to 89mm. In 1956 the 600 models (actually displacing 596cc) showed up, with the bore increased to 68mm, the stroke to 82mm. The 497cc Model 7 had a modestly undersquare engine, with a bore of 66mm, stroke, 72.6mm, and the 500 twins stayed true to that until the last 88SS rolled off the line in 1966. Here we will take a moment to look at enlargement technology. ![]() This particular design put the single camshaft up forward of the cylinders, spun by a chain driven via the right-side timing case later the chain would be replaced by gears. Following World War II Norton was one of the first to jump on Turner’s vertical-twin bandwagon, with the Model 7 Dominator in the popular half-liter class. Norton died in 1925, just as his singles were hitting their stride on the racing circuit. He began building motorized bicycles in 1902, followed by V-twin models, and then a series of exceptional side-valve, OHV and OHC singles.
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