Lot details Registration No: JVS 832 Frame No: S76407 Engine No: SB10438 cc: 500 MOT Expiry Date: None
The Sunbeam concern had been acquired by BSA during 1943 and a new machine bearing the Sunbeam name was described to the press in early 1946. The new model was intended as the "group flagship" and consequently, Erling Poppe, its chief architect, designed a machine that incorporated many innovative features. The short-stroke, overhead cam, in line twin cylinder engine was mated to a shaft final drive via a four speed gearbox with an under slung "worm" gear transmitting the drive to the rear wheel. The all alloy engine and gearbox were mounted in a duplex frame equipped with plunger rear suspension, telescopic forks, 16 inch balloon tyres and sprung saddle all contributed to providing a comfortable ride. However, harsh running, a peaky power delivery and rapid wear of the worm gear had been identified during pre production testing which resulted in the models release being delayed until 1947 whilst solutions were sought. The BSA design staff opted to detune the engine which rectified the worm gear wear and to rubber mount the engine and gearbox which addressed the harshness issue. Unfortunately the reduction in power output combined with the machines weight of 400lbs resulted in less than spectacular performance with the machine struggling to exceed 75mph when tested, consequently in a lot of cases potential buyers admired the technical specification but opted for the quicker and cheaper parallel twins then available. In response to the poor sales BSA introduced a revised model, adopting standard BSA forks housed in special yokes, during 1949 together with a lighter, more sporting model variant typed the S8. The S8 reverted to normal section tyres and employed standard BSA forks and front brake. The two machines continued to be offered until 1957, selling steadily to their target market of discerning enthusiasts a, trend that continues today.
This example dating from 1954 has formed part of a private collection for a number of years and is offered with a Swansea V5C. It is presented in the green livery synonymous with the model and is equipped with a rear carrier and sprung pillion seat and is offered with a number of old MOT certificates and a spares price list.
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