Photo ou archives : D. Ganneau
1117
PRAGA
500 cc DOHC -1930
Czech innovation
]. F. Koch of Prague created his first motorcycle, the "JFK," in 1923. It was a 350cc single with a single overhead camshaft set longitudinally (though the crankshaft followed the normal transverse layout). In 1926, Koch was recruited by the BD (Breitfeld-Danek) firm and designed for them a touring with twin overhead camshafts, a layout not previously used on a mass production bike. Nor was that the sole originality of this machine, for the gearbox could be taken out sideways, as on modern Grand Prix machines.
Help from the Automobile Industry
BD was taken over in 1929 by the leading Czech automobile company, Praga, which continued the production of this 500 with some success: 2500 examples of this machine were built up to 1933, in five mildly different versions. A 350 SOHC whose crankshaft and overhead camshaft were both set longitudinally was built alongside the 500 from 1930, but its production was tiny.
Koch Goes Back to the Beginning
When Praga pulled out of motorcycles in 1933, Koch went back to zero by launching a 350 with a transverse overhead camshaft under his own name. Its career was shortlived and led Koch to join CZ in 1935. Praga's place in history is assured as the first series production DOHC machine. While such engines have strong racing overtones, in this case the end result was a tame machine well suited to the fitting of a sidecar.
SPECIFICATIONS
Engine: 499cc (84x90mm) air-cooled single cylinder four-stroke; pressure lubrication
Power Rating: 18 hp
Valves: Double overhead camshaft driven by shaft and gears
Fuel System: carburetor
Transmission: 3-speed hand change; chain
final drive
Suspension: girder forks (front); rigid (rear)
Brakes: drum (front & rear)
Wheels: wire
Weight: 276 lb
Maximum Speed: 109 mph
Though twin overhead camshafts normally impart a sporting image, the Praga was actually a touring bike with no pretensions to performance.