1937 Sunbeam Model 14 Sports 250cc

Sunbeam Cycles made by John Marston Limited of Wolverhampton was a British brand of bicycles[1] and, from 1912 to 1956 motorcycles.

John Marston Limited never produced a flat-tank 250, and it wasn’t until 1933 that they entered this particular sector of the market. They did so the easy way, by simply reducing the stroke of the existing 347cc Model 8 from 70 to 59mm, and retaining the Model 8’s rolling chassis. They called it, very aptly but confusingly for some, the 250 Longstroke, or Model 14. Complete with twin-port head, the machine looked very like a scaled-down Model 9, but it was inevitably rather over-weight.

As Found

Later in 1936, JML announced what they rather awkwardly called a Semi-Sports version of the 250, with upswept exhaust pipe, larger front wheel (3.00 x 21) and sports mudguards. The 250 continued for 1937, in standard form, and as a more sensibly-named Sports. In both cases the engine had been further tidied with an internal oil pump reducing the external pipework, and a flange-mounted downdraft carburetor was fitted. The Sports was graced by a very handsome chrome-plated petrol tank, with gold and blue lining. The magnificent 5” speedometer could also now be specified. The Sports was fitted with a high-compression piston giving 7.5:1 against 7:1 for the standard model.


The core engine was acquired in the UK. The parts needed to make it a complete engine came from Australia, Canada, Germany, the UK, and the USA. Other miscellaneous parts were sourced in countries not mentioned above.      

Sunbeam Motorcycle Manual
Sunbeam Spare Parts List