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BSA M24

Make Model	BSA M24 (1938 specifications)
Year	1937 - 61
Engine	Four stroke single cylinder, OHV
Capacity	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
Ignition	Lucas magdyno
Clutch	Multi-plate cush drive
Transmission	4-Speed
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
Colours	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"