BSA B25 Gold Star

23 Apr 2015 | Author: | Comments Off on BSA B25 Gold Star
BSA B 25 Star

The story of the BSA Gold Star goes way back to I937 when the Small Health company introduced a new 500cc single cylinder model called the Empire Star. At that time a gold star was awarded at the Brooklands circuit to any rider who managed to lap at over I00 mph during a race.

The staff at BSA wondered if their new sporty single could be tuned up in order to win one of the prizes, although they had not entered into competition since I92I when all six of their sloper models failed to finish in the Senior T.T. But they decided to try, and recruited the retired Wal Handley for the purpose. On 30 June I937 the scene was set.

Handley was entered in a three-lap outer circuit event and by the second lap he had fought his way to the front of the field, finally finishing several hundred yards ahead. His average speed was I02-27 mph with one amazing lap of l07-57mph! The public were impressed, Handley went home with his gold star, and BSA got more publicity than they could have imagined.

At the Earls Court Show the following year a replica of that famous machine was on show and, of course, it was called the Gold Star.

The Gold Star received the model number M24 but the production model was certainly quite different to Handley’s mount. Instead of an iron cylinder head and barrel the 496 cc single was fitted with aluminium equivalents with an austenitic iron liner and valve seat inserts. The valve gear was enclosed and lubricated by a pressure-feed dry sump system with the oil tank situated beneath the saddle.

Drive to the rear wheel was by chain and this came via a four speed Elektron gearbox and a multi-plate clutch. The mixture was drawn into the engine by an Amal TT type carburettor, with the exception of a track model which came fitted with a twin-float carburettor and various other performance parts. Nevertheless, each proud owner had the satisfaction of knowing that his engine was individually built and bench-tested by BSA.

Each power unit fitted neatly into a triangular cradle type frame that was made from high tensile steel tubing. At the front there were tubular forks with an adjustable damper unit, while the rear end remained solid as on most machines of the period. Considering the weight of some present-day machines the Gold Star was light, tipping the scales at a mere 3I5 lbs including lights and accessories.

Starting the big single was easy —as long as you knew how! First, it was necessary to flood the carburettor, secondly retard the ignition and finally find the compression stroke while in gear. Once neutral had again been located a quick prod in the kickstarter usually brought the beast to life.

The performance of the Gold Star was commendable. Acceleration from standstill was very brisk and when the four-speed gearbox was used to the full a top speed of around 90 mph could be achieved. For normal cruising, though, the engine felt best at a speed of around 70 mph.

Fuel consumption was generally in the region of 64mpg, thus giving a potential tank range of almost 200 miles.

With its superb handling whatever hazard lay ahead, the bike would keep on line and was never deflected off course even in adverse road conditions. Brakes consisted of 7 in by I-3/8 in drums at both front and rear with smooth but powerful action. From 30 mph the stopping distance was 28 feet, a figure on par with its modern counterparts.

In I940 the war prevented further production of the big single and the factory concentrated on building its khaki cousin, the M20. Nevertheless, the model returned in I948, appearing first as a 350 and later as a 500, each with telescopic front forks. A few years later the design was again revised and many performance parts were offered that could transform the basic roadster into a clubman’s racer.

Consequently the Clubman’s TT was inundated with Gold Stars but it was not only at road racing that the model excelled. In trials and scrambling the bike took many awards and over the years it was again substantially redesigned, but in I963 the machine saw its last year of production and the Gold Star faded forever.


BSA B 25 Star
BSA B 25 Star

Specification

(1938 model) engine

Air-cooled, four-stroke, single-cylinder. 82 mm (3-46 in) bore x 94 mm (3-70 in) stroke = 496 cc (30-26 cu in). Maximum power 30 bhp at 5800 rpm. Two valves each operated via push-rods.

Single Amal TT carburettor transmission Four-speed gearbox. Chain drive to rear wheel frame

Triangulated cradle suspension

Front – Tubular forks with adjustable damper unit Rear – Solid rear end brakes

Front – Single drum Rear – Single drum

BSA B 25 Star
BSA B 25 Star
BSA B 25 Star
BSA B 25 Star
BSA B 25 Star

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