1967 Jawa 350 V4 Type G73A
Engine: 345cc water-cooled 2-stroke rotary valve 30-degree V4, 48mm x 47.6mm (359cc, 49mm x 47.6mm as tested), 16:1 compression ratio, 68hp @ 13,200rpm
Top speed: 162mph
Carburetion: Four 27mm Amal GP
Transmission: 7-speed, chain final drive
Electrics: 12v, electronic CDI ignition
Frame/wheelbase: Open-cradle tubular steel frame with engine as semi-stressed member/53.1in (1,350mm)
Suspension: Telescopic fork front, dual Girling shocks w/adjustable preload rear
Brakes: 9in (230mm) 4LS magnesium drum front, 8.7in (220mm) SLS magnesium drum rear
Tires: 2.75 x 18in front, 3.5 x 18in rear
Weight (dry): 303.6lb (138kg)
During the 1950s-1960s classic era of road racing, Czechoslovakia was the only Iron Curtain country to mount a sustained challenge to Italian and Japanese supremacy in the prestigious large capacity classes. Sure, East Germany’s MZ revolutionized Grand Prix racing’s 125cc and 250cc technology, but only the state-owned Czech Jawa and its CZ sister marque flew the Eastern bloc flag in the 350cc and 500cc categories with any measure of success.
Founded in 1929 by Frantisek Janecek as a spinoff from his successful armaments business, Jawa embraced racing from the beginning. Its finest hour arguably came in 1961, when legendary rider Franta Stastny finished second in the 350cc World Championship to MV Agusta’s Gary Hocking aboard his double overhead cam Jawa 4-stroke parallel twin. As the 1960s unfolded, Jawa designer Zdenek Tichy was one of the first Europeans to recognize the future direction of road racing development, designing a series of 2-stroke GP racers that gradually replaced Jawa’s 4-stroke twins on the racetrack.
Jawa initially built 250cc and 350cc singles aimed at the Eastern Bloc privateer customer, but in 1966 Tichy and his men began working on air-cooled, rotary-valve 125/250/350cc V-twins. These provided the template for the technology incorporated in the water-cooled Jawa “Typ” (the Czech spelling of “type”) 673 350cc V4, which made its debut in the 1967 Dutch TT at Assen in the hands of Gustav Havel. It proved unreliable, seizing three times in practice and again in the race. A key issue was Jawa’s inability to obtain the quality raw materials that were available to teams in Western Europe and Japan. The sometimes extreme variations in rates of expansion between the various components comprising their engines meant seizure was a constant issue with the 2-stroke Jawas.
Nevertheless, the 350cc V4 Jawa 2-stroke engine was a leading-edge design that followed a similar format to the rotary-valve V4 Yamahas that dominated the 125cc/250cc World Championships in 1967-1968. But the Czech V4’s 35-degree angle was more compact than the Yamahas’, resulting in a lower and more aerodynamic frontal profile. It featured four separate crankshafts, each pair coupled via splines to a large central straight-cut gear pinion connected to an intermediate shaft. This transferred power to the clutch and also drove the ignition system, as well as the water pump and a separate oil pump introduced later.
Order the July/August 2016 issue of Motorcycle Classics to read more about the 1967 Jawa 350 V4 Type 673A. Contact Customer Service at (800) 880-7567 or contact us by email.