Sparton
Sparton were motorcycles produced from 1975 to 1982, and resulted from a link between Barton Engineering and Spondon Engineering.
The former built racing two-stroke engines, the latter produced frames and the basis came from work carried out by Barry Hart, of Caernarfon, in Gwynned, North Wales, who tuned Suzuki triples.
In 1975 a machine was built that had a 500cc square-four engine modelled on the Suzuki RG500, but with very different detail. From this came the Phoenix 500cc and 750cc fours that became famous as the Silver Dream Racer in the film that starred David Essex.
The firm later became involved with CCM and Armstrong but eventually they were overtaken by the Japanese who had endless funding and continued development.
Sources of Information
The British Motorcycle Directory - Over 1,100 Marques from 1888 - by Roy Bacon and Ken Hallworth. Pub: The Crowood Press 2004 ISBN 1 86126 674 X