Like the majority of their contemporaries, Norton relied on the sidevalve engine until the introduction of its first overhead-valve design in 1922, and the resulting Norton Model 18 was a big success on the road.

On the racetrack however, Velocette had shown the way forward when its overhead-camshaft KTT romped away from the field in the 1926 Junior TT, and Norton responded with its own similar engine the following year.

Designed by Walter Moore, the Norton motor retained the firm’s traditional 79x100mm bore and stroke dimensions, employing bevel gears and a vertical shaft to drive the cams in KTT fashion. The cycle parts too were new, a cradle frame and saddle tank appearing for the first time on the works CS1 racer, which scored a debut win in the 1927 Isle of Man Senior TT with Alec Bennett riding.

The production version of the new CS1 duly appeared at the Motor Cycle Show later that same year and continued as Norton’s top-of-the-range sports machine until the introduction of the International.

Today this rare landmark model is one of the most sought after of all Norton motorcycles.

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