BSA B "Round tank"


Make Model





Four stroke , single cylinder, side valve


249 cc / 15.2 cub in

Bore and Stroke

63 x 80 mm
Exhaust Single, stainless steel
Ignition Magneto
Battery 6V
Starting Slip on kick starter

Max Power

1.83 kW / 2.49 hp



Final Drive


Seat height

Upwards adjustable from 711 mm / 28 in. lowest setting
Front Suspension Single spring girder fork
Rear Suspension None, spring loaded saddle

Front Tyre

2.25 x 24

Rear Tyre

2.25 x 24

Front Brakes


Rear Brakes

Hand lever and foot pedal woking independently on rear wheel dummy rim


77 kg / 170 lbs

Average fuel consumption

2.35 L/100 km / 42.5 km/l / 100 US mpg

Top speed

72 km/h / 45 mph

BSA was justly proud and underlined their pride with a bold fuel tank finish. In keeping with period trends the tank served both fuel and oil needs, but its cylindrical shape bucked then current trends, looking as though it ought to grace a lawnmower.

Instead of hiding it, BSA painted the tank bright green and emblazoned it with panels, lines and logos.  And it is the tank which gave Model B its hindsight name.

As many British moped and two-stroke riders from the 1950s and 1960s know, riding a small low-powered machine makes you the lowest of the low in the eyes of some.  No different in the 1920s and along with the sarcastic comments Model B riders copped for a few including famously mower tank, marrow tank, cucumber tank and round tank.  Round tank stuck, BSA successfully banked this inverse praise and Round Tank owners are justly proud today.