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The Marston Sunbeam Club & Register

The 59 x 90 OHV 250s, 1933 to 1938

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.

250 Longstroke/Model14

250 cc Longstroke  Model 14

Later in 1933 JML surprised the market with a super-sports version of the Model 14, which they called the Little 90. This really was a racer in miniature, looking very like the “big” Model 90, with a single-port head, downdraught TT carburettor, bum pad and the notorious Sunbeam positive-stop foot gearchange.

Little 90

250 cc Little 90

These 250cc Longstroke continued for 1934, but was replaced by a new model, the 248cc Model 16, for 1935. The Little 90 meanwhile was superseded for 1934 by the Little 95, looking very like a scaled-down version of the Model 95. It featured a much larger petrol tank, a downdraught flange mounted TT carburettor, and a compression ratio raised to 8.4:1.

Little 95

250 cc Little 95

The M16 having proved unsuccessful, for 1936 JML re-introduced the Model 14, albeit in a much modified form, with the “Longstroke” tag now dropped. The new 250, in common with the new Model 8, featured a duplex cradle frame, larger tank and, most importantly, a Burman four-speed gearbox. The engine was also tidied up significantly but retained the 59 x 90 bore and stroke, most parts being common to the Model 8.

Model 14

250cc Model 14

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.

Semi-Sports

250 cc Semi Sports

 

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 carburettor 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.

Sports

250cc Sports

These were among the models taken over by AMC who continued to manufacture from Wolverhampton stock, with the 1938 models virtually identical to 1937. Some changes were made over the course of the 1938 model year, mainly to incorporate AMC-designed parts where the Wolverhampton stock was used up. This does cause considerable head-scratching for restorers of these machines, but the AMC spares book is very comprehensive, and the changes are well tracked.

This was the last year of the 59 x 90 250, with the new B-series machines coming on stream for the 1939 model year.

 

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The Marston Sunbeam Club & Register Ltd is a company limited by guarantee registered in England and Wales Registration No. 7230550 - Registered office: Lewis Onions Solicitors, Allium House, 36 Water Street, Birmingham B3 1HP

 

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