1977 JAWA 250 Grand Prix Twin
1977 JAWA 250 Grand Prix Twin
Last attempt at Grands Prix
After a 250 with rotary intake valve launched in 1965, Jawa tried to oppose the Japanese with the same sophistication and competed in the 1967 Grand Prix with this extraordinary 350 four-cylinder two-stroke, ridden initially by Bill Ivy and then by Silvio Grassetti.
No Funding
Lack of funds meant that this bike never fully realized its potential, and when new rules limited the 250 and 350 class to twins, in the early 1970s, Jawa used a 250 two-stroke twin with conventional intake porting that proved powerless against the Yamahas.
A Brave Attempt
Still lacking finances, Jawa obstinately developed a completely new 250 in late 1976, which returned to rotary intake valves and its original techniques. As the works could not guarantee its development into an internationally-competitive machine, it finally retired from Grands Prix at the end of 1977, to concentrate on off- road events. The concept of this 250 was based on experience gained with the four-cylinder racer. Jawa had worked hard to minimize the size of the rotary intake valves, the pistons had only a single ring and, as on the Jawa enduro bikes, the connecting rods ran on uncaged needle roller bearings. In the gearbox, the sliding cogs were mounted on roller bearings. The great originality of this bike was its one- piece crankcase with a floating baffle mounted on the central bearing housing supporting the primary drive gear, within which the two separate crankshafts were coupled. The crankshafts and gear cluster could be removed without taking the engine from the frame.
SPECIFICATIONS
Engine: 246cc (56×50mm) water-cooled twin- cylinder; Krobcr electronic ignition and water pomp driven by vertical shaft behind cylinders Power Rating: 44 hp @ 12,000 rpm
Valves: two-stroke; rotary intake valves
Fuel System: two Mikuni 34mm carburetors Transmission: 6-speed, dry multi-plate clutch; chain final drive
Suspension: telescopic forks (front); swing arm (rear)
Brakes: twin discs (front); disc (rear)
Wheels: 18 inch (front & rear)
The 250 Jawa, shown here in 1977, appeared for the last time in 1978 with a British-made Baxton frame with monoshock rear suspension replacing the molybdenum steel original.
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