BSA B44
The BSA B44 was a series of unit construction single-cylinder OHV four-stroke motorcycles made by the Birmingham Small Arms Company between 1966 and 1970. The machines were developed from the BSA World Championship Motocross machines, which were themselves based on the C15/B40.
Background
In 1963 BSA began competing a C15T fitted with the B40 engine in various classes. Works rider Jeff Smith won the Scottish Six Days 350 cc cup that year and finished 3rd in the 500 cc Motocross World Championship.Brian Martin, head of BSA's competition department, started a feasibility study to enlarge the B40 engine. The engine was enlarged to, which was considered the maximum reliable size. For the 1964 Motocross season, the engine was fitted in a lightweight frame that carried the oil in the top tube. The machine weighed. Smith took this machine to 3 victories in the championship, and with 3 rounds to go, the displacement was increased to. Smith won the final three rounds and beat the winner of the two previous championships, Swede Rolf Tibblin, to the title by a narrow margin.
Smith was dominant in the 1965 season on the 441 and had the title sewn up half-way through the season. In the final race, the East German GP, Smith used a pre-production model of the soon-to-be-announced Victor GP and finished sixth.
Technical Details
The 441 cc engine, developed by the BSA Competitions Department, was based on the B40. The extra capacity was obtained by increasing the B40's 70 mm stroke to 90 mm, the 79 mm bore was retained. To strengthen the bottom end, the timing side main bearing was changed from a plain bush to a ball bearing, and the drive side main bearing was changed from a ball to a roller bearing. The cast iron barrel of the B40 was changed to an alloy item for the 441. Compression ratio of the GP model was 11.4:1, and was reduced to 9.5:1 on the Enduro by means of a plate below the barrel.In 1967, the Victor Roadster was introduced, which had a square-finned barrel and head and a compression ration of 9.4:1. The Enduro version was fitted with this configuration in 1968. Power output was for the GP models and ) for the other models.
The GP featured a frame derived from the works racers, other models used a frame developed from the C15 Trials bikes.
Models
B44 Victor GP
On the strength of Jeff Smith's two World Championship victories, BSA introduced a race replica at the 1965 Earls Court Motorcycle Show, the B44 Victor GP.The model was discontinued in 1967, around 500 GPs being produced in total.