- Manufacturer: BSA
- Model: BB 31
- Engine: 350 cc
- Year: 1953
- Decade: 1950s
- Machine Type: Custom/Special
The BSA B31, introduced in 1945, is the first new model introduced by the company after the Second World War. Based on the design before the war, it uses four-stroke single cylinder engine displaced 348 cc (21.2 cu in). Initially, the rigid frame and telescopic forks, the first such use of the BSA. It was developed around 17 bhp (13 kW), enough for the streets day and enough to give a top speed of about 70 mph (110 km / h). It was immediately popular and was soon joined by 500 cc (31 cu in) version, and equal competition BSA B33, BSA and BSA B32 B34, next version of the car, with stiffer suspension and different end demultiplication, known as BB31.
Plunger rear suspension offered later, with a frame suspension Rear suspension is available from 1954. This model continued in production until 1959, when Lucas magdyno which traditionally has been replaced by an alternator and ignition coil.
Series B extended through his life to enter the famous BSA Gold Star, and the bottom half of all engines have many similarities with the model of the valve series M. The M33, designed to work side by side, the M series combined a strong frame and perform better on the valve 500 cc B33.
