Make Model

BSA M24 (1938 specifications)


1937 - 61


Four stroke single cylinder, OHV


498 cc / 30.4 in

Bore x Stroke

82 x 94 mm

Cooling System Air cooled
Lubrication Dry sump
Carburetor Amal 10TT
Exhaust Single, chrome


Lucas magdyno
Clutch Multi-plate cush drive


Final Drive Chain
Frame Triangulated cradle type
Wheelbase 1372 mm / 54 in.
Ground Clearance 121 mm / 4.75 in
Saddle Height 724 mm / 28.5 in.

Front Suspension

Quick adjustable shock absorbers with steering damper

Rear Suspension

None, spring loaded saddle

Front Brakes

Drum, 7.5 in


Rear Brakes

Drum, 7.5 in
Wheels Steel, laced spokes

Front Tyre

3.00 x 20 in, Dunlop Universal

Rear Tyre

3.25 x 19 in, Dunlop Universal

Fuel Capacity 

13.6 L / 3.6 US gal


Black/chrome, Chrome/matt silver

Following the arrival at BSA in 1936 of Val Page, the new range of motorcycles for 1937 revealed a significant redesign of the single cylinder engines, with the adoption of dry sump lubrication. The all new M20 500cc side-valve engine, and the M19, M22 & M23 OHV engines as pictured above, were to form the basis for all larger capacity BSA single cylinder engines until the final 500cc Gold Star in 1962.

Based very closely on the 500cc M23 Empire Star, first produced for 1937, the 1938 production model Gold Star shared most of the older model’s cycle parts, except the frame, which was constructed of lighter Reynolds 531 high-tensile tubing, the petrol tank, which was unique to the Gold Star in having an integral tool box in the top, in place of the instrument panel, and the rear brake drum which sported thin fins around its diameter. The ammeter and light switch were housed in a panel in the headlamp shell. The other main visible differences were the all-alloy engine with built-in pushrod tunnel, the TT carburettor, and the “Elektron” gearbox cases. The M24 also had a small tubular oil pressure indicator mounted above the timing case in place of an indicator button in the tank top instrument panel of the M23. The first production M24s , bearing Engine and Frame numbers starting at 101 and prefixed JM24, were built in November/December 1937, and the first batch of 10 were dispatched on 17th December.

Production of 1938 Gold Stars continued until the autumn of 1938, when the factory switched to production of the new 1939 model. The last one, engine JM24 365, in frame JM24 404, was dispatched on 6th July 1939 to the British Army for the 1939 ISDT.

A total of approximately 266 1938 JM24 bikes were built, and of these, 85 were despatched to destinations outside the UK.

"M24 competition model"