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BMW 500 Rennsport 1954
After supercharging was abolished on racing motorcycles, BMW
had no choice but to modify its fine two-cylinder opposed-piston engines. And in
1951 the German company introduced the Mustang, which was similar to the old
model that had won the 1938 world championship except for the absence of the
supercharger and the introduction of a front-fork telescopic suspension. The
supercharger was replaced by an air-feed with two carburetors.
The BMW Mustang, however, proved not to be on a par with
competing motorcycles. It could not stand up to the Italian multicylinder models
or to the British single- and double-cylinders. As a result the Mustang was soon
retired. It was replaced in
1953 by the 500 Rennsport model.
The BMW 500 Rennsport had an altogether new engine. The
dimensions of the cylinders were changed and the engine's power and weight were
different. The opposed-piston system was maintained, as were the double
single-shaft distribution and the carburetor feed. A great deal of work was done
on the chassis, the Achilles' heel of the vehicles produced by BMW.
The motorcycle was totally redesigned and looked very
up-to-date. It had a double cradle and a swinging fork enclosing the
transmission shaft. There were telescopic shock absorbers on the rear wheel,
while the front wheel had fork suspension of the Earles type. The motorcycle's
total weight came to barely 275
BMW Rennsport with carburetor engine, 1953 model
pounds, which shows how carefully the two-wheeler was designed. After testing
the prototype, BMW tried to introduce a new technical feature that same
year—injector feed. The BMW technicians settled on direct injection with a Bosch
pump.
The BMW 500 Rennsport was brand-new and proved to be highly
competitive. Racers liked the motorcycle for riding on very fast circuits, where
they could keep the throttle almost constantly open.
The Rennsport never became a great success, chiefly because of problems with
instability. The engine was certainly one of the most powerful around, but only
a few racers, one of them being the legendary Zel-ler, managed to win races with
it.
When the Rennsport engine was first mounted with a sidecar,
however, the results were excellent. All the problems of stability were
eliminated by the third wheel. In sidecar racing the BMW 500 knew no rivals.
Victories in sidecar racing gradually diverted BMW's attention from other races,
and in 1958 the company withdrew from racing two-wheelers altogether.
Motorcycle: BMW 500 Rennsport Manufacturer: BMW, Munich Type:
Racing Year: 1954
Engine: BMW two-cylinder, opposed-piston, 180°. Four-stroke cycle. Double
overhead single-shaft distribution, with bevel gear shaft. Direct injection with
Bosch pump. Displacement 493.9 cc. (68 mm. x 68 mm.)
Cooling: Air
Transmission: Four-speed block. Final transmission by cardanic shaft
Power: About 60 h.p. at 9,500 r.p.m.
Maximum speed: About 143 m.p.h.
Chassis: Continuous, double cradle. Front wheel, Earles suspension; rear,
telescopic shock absorbers
Brakes: Front and rear, central drum
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