Martinsyde 1921 6 HP 678 cc 2 cyl EOI 3507

Martinsyde 1921 6 HP 678 cc exhaust-over-inlet V-twin frame # NO933 engine # H933

The British firm of Martinsyde was founded in 1908 when Helmuth Paul Martin and George Harris Handasyde went into partnership to build aircraft. By the end of WWI Martinsyde was Britain’s third largest aircraft manufacturer, occupying sites at Brooklands and Maybury Hill in Woking. Faced with a sharp downturn in demand for its products, the firm turned to motorcycle production after the war’s end, having acquired the rights to an exhaust-over-inlet engine, provided by Howard Newman, whose family business produced the Ivy motorcycles. It appears Newman acquired the design from a draughtsman formerly employed by the Blackburne firm and sold it for £5,000 to Martinsyde.
The gearbox and clutch were AJS designed, and made under licence at the Martinsyde works, as were the Brampton Biflex forks.
Problems caused by unsatisfactory frame components having been overcome, Martinsyde motorcycle production got properly underway in 1920. The company’s first machines, powered by Newman’s 678 cc 50 degree V-twin engine, were marketed as Martinsyde-Newman, which was abbreviated to simply Martinsyde after Newman departed in the course of 1920.
The exhaust-over-inlet design was unique for a British-designed engine, although the theory behind it sounded quite logical. In the December 1, 1920 Olympia Report of “Motor Cycling” we read: “The chief mechanical feature of all Martinsyde models is the system of superimposing the exhaust valve over the inlet. This system ensures that the hottest part of the engine, which is invariable around the exhaust port, is away from the working bore of the cylinder, and distortion of piston and cylinder is thereby prevented. This claim is fully borne out in practice, for the Martinsyde is a remarkably cool running engine and one that will maintain a high speed without distress.”
Although Martinsyde got good publicity from competition successes at Brooklands and at the Scottish Six Days Trial, sales were modest and the introduction of 496 cc and 738 cc twins and a 347 cc single didn’t bring the hoped-for sales increase. In July 1922 the factory got damaged by fire and the financial problems this caused hastened the end; in 1923 the firm’s name and remaining stock being acquired by BAT. The last complete Martinsyde was sold in 1923 and, according to info from the Martinsyde Register, less than 40 of the around 2,000 produced are known to have survived.

The machine we present is an older restoration and is fitted with updated brakes of the internal-expanding type, which ensure better performance. She has been part of a static private collection for years and will benefit from a good check over before returning to the road.