On the 3 November 1916 civilian production was suspended by the British Government's Ministry of Munitions. John Marston Ltd issued an over-stamped 1916 catalogue for 1917. 1916 machines were available from stock.
As a result of the Russian Government's decision in 1916 to mechanise its army, Marston's was contracted by the Ministry of Munitions to supply 850 v-twin 8 h.p. side-car machines and 500 solo machines. Despite the Tsar being deposed in April 1917 the contract continued until the summer of 1917.
The 3½ h.p. Sunbeam solo machine was considered too low a capacity for the Russian Government. Their specification resulted in Marston producing a v-twin solo machine using a 5 h.p. (654cc) JAP engine installed in a modified 3½ h.p. frame.
Similarly, the 8 h.p. MAG-engined model from 1916 was modified to take an 8 h.p. JAP engine of 996cc (85.5x85mm). A slightly altered frame, increasing the wheel-base from 60 inches to 61.5 inches, and larger 28 inch wheels provided the space and ground clearance for the JAP-engine.
The belt-driven French military model which had commenced production the previous year continued.
Sources:
* Robert Cordon Champ, 1980, 'The Sunbeam Motorcycle'. Haynes Publishing.
* The Motor Cycle, May 3rd 1917 (thanks to Juris Ramba, Latvia and Annice Collett, librarian at the Vintage Motor Cycle Club)
* Stephen J Mills, 1994, 'AJS of Wolverhampton'. Published by the Author (for details of the Russian Government contract).
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