A development of the 350cc B31, the 500cc B33 was manufactured from 1947 to 1960. BSA's rugged, workaday B31 was a new introduction for 1945, its overhead-valve engine providing the basis for the renowned Gold Star sports roadster. At the time of its introduction, the B31 was BSA's sole all-new model, joining the lightweight 'C' and heavyweight 'M' ranges carried over from pre-war days. Produced initially with rigid frame and telescopic forks, the B31 was available from 1949 with optional plunger rear suspension and switched to a swinging-arm frame, along with the rest of the range, in 1954. The B33 engine closely followed B31 lines but with larger (85mm) bore and heavier flywheels, while cycle parts were identical apart from a larger-section rear tyre. A good, solid, all-round performer by the standards of its day, the B33 could top 80mph, cruise comfortably all day at 70mph and return in excess of 70mpg.
This extensively modified B33 was imported from the USA and has not been used since its arrival in this country. Import duties have been paid and the machine comes with a US Certificate of Title. It should be noted that the engine dates from 1955 and that the frame, although numbered as a 1947 'rigid', has the plunger rear suspension first introduced for 1949.