MOTOBÉCANE

500 Injection - 1974

Too far ahead of its time

Faced with an onslaught from the Japanese factories in the Seventies, the only way for European manufacturers to survive seemed to be to produce technically-advanced, original machines. Following this reasoning, in 1973 Eric Jaulmes, technical director of the French Motobécane company (assisted by his son Christian) developed a system of semi-direct fuel injection for the firm's 350cc triple.

Injection Purge

At the time this was a unique installation on a two-stroke; today it represents the direction that this type of engine must take to assure its future – not only does fuel injection increase power, as on a four-stroke, but it reduces fuel consumption and pollution, thanks to a purge of clean air.

Photoelectric Cell

The originality of the Motobécane system lay in the use of a photoelectric cell with a disc of varying opacity in its field of vision to control the volume of fuel injected. The angular position of the disc and the radial position of the photoelectric cell were controlled by the speed and load demands of the engine; the fuel injectors were specially engineered by Bosch to minimize throttle lag. This revolutionary form of fuel injection never reached the market, however, since the poor sales of the 350 led to its withdrawal before this amazing system, 20 years ahead of its time, could be put into production.

SPECIFICATIONS

Engine: 500cc three-cylinder two-stroke

Power Rating: 40+ hp

Valves: two-stroke

Fuel System: Bosch "opto-electronic" fuel injection

Transmission: 5-speed

Suspension: (from) telescopic forks; (rear) swinging arm

Brakes: (front) disk; (rear) drum

Wheels: 18 in wire

Weight: 400 lb

Maximum Speed: 100 mph

Absolutely indistinguishable externally from the production 350, the 500 only existed in prototype form, and most of the tests were carried out on a 350.