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 BSA - 350 B 25 Empire Star
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Photo ou archives : F-M. Dumas

Capacity : 350
Model : B 25 Empire Star
Production : 1939 - 1939
Category : (Off-Road) Trial


350cc B25 / Empire Star - 1939

Star for a season

The new range of BSA sports singles debuted in late 1938, but production was halted in 1939 when the factory switched to military materiel such as its side-valve M20 500.

It's That Man Again ...

The top of the 1939 BSA sports range was the M24 Gold Star. It took its name from the exploits of Wal Handley (who was also a BSA dealer), who returned to the track by lapping Brooklands with the prototype at 107.6 mph, winning the "Gold Star," awarded by the British Racing Motorcycle Club to any rider making a lap at over 100 mph. The BSA Gold Star had an aluminum engine, but the more affordable Silver Star 250 B21, 350 B24 and 500 M23 had cast-iron cylinders and heads.

Ready to Compete

The B25 Empire Star trials 350 was sold ready to compete and was one of the most sought-after mounts for the popular one-day trials in Great Britain. The engine retained the bore and stroke measurements traditionally used by BSA, but the engine internals were polished and a healthy 18 hp resulted. The cast-iron cylinder and head underwent special treatment, and consequently, specific piston rings had to be used. The four-speed gearbox incorporated a high fourth for use in the zones between trials stages and an ultralow first so that the machine could haul itself out of the impossible quagmires that constituted one of the most recurrent trial hazards. The B25's frame was made of Reynolds 531 tubing, and the bike was sold with lighting (normally removed for trials) and high-level exhaust system.


Engine: 348cc (71x88mm) air-cooled single-cylinder four-stroke; magneto ignition

Power Rating: 18 hp @ 5500 rpm

Valves: overhead

Fuel System: Amal carburetor

Transmission: 4-speed, chain final drive

Suspension: girder forks (front); rigid (rear)

Brakes: 5.5 inch drum (front); 7 inch drum (rear)

Wheels: 2.75x21 inch (front); 4.00x19 inch (rear)

Weight: 320 lb

Maximum Speed: 80 mph

The B25 Empire Star 350 was only built during the 1939 season, and this superbly restored example is possibly the sole survivor.

Le fichier Moto Passion réalisé par François-Marie Dumas réunit près de deux mille photos accompagnées d'un historique très complet des machines présentées.
Il sera progressivement mis à jour ici et toute information complémentaire est la bienvenue sur info@moto-collection.org.

Cette documentation unique, qui constitue sans doute l'encyclopédie la plus exhaustive jamais écrite sur l'histoire de la moto, a été réalisée avec l'assistance de nombreux spécialistes dont principalement Didier Ganneau, Christophe Gaime, Mick Woollett, Jean Goyard, Bernard Salvat, Christian Rey, Yves Campion, Helmut Krackowizer, Michael Dregni, Michel Montange, etc. que je remercie ici.

Disponible sur demande :
- Les fiches originales sur papier
- Les photos et archives signées de mon nom en haute définition ou les documents originaux.
Me contacter sur info@moto-collection.org pour les conditions et droits d'utilisation.