Jackson-Rotrax was a motorcycle produced from 1946 to approximately 1976.
This was a speedway machine that appeared after the end of the Second World War. Fitted with a 500cc JAP engine running on alcohol fuel, and a countershaft carrying the clutch mounted in a rigid frame, the machine was well finished and well made.
It was most successful in its task for many years, and although various engines were used, it was the JAP that predominated for many years.
Sources of Information
The British Motorcycle Directory - Over 1,100 Marques from 1888 - by Roy Bacon and Ken Hallworth. Pub: The Crowood Press