Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125814
~ w Z W ...J o > o U.S. National 500 class champion Brad Lackey continues R&D riding of the 450 prototype. KAWASAKI 450 PROTOTYPICAL DATA (Designated F-12MX in production) Engine 450cc two-stroke piston-port single Bore x Stroke ...................................•86mm x 76mm Compression Ratio 6.5: 1 Ignition Magneto COl Carburetion 34mm Mikuni Starting .........•..•...•..•............ Primary kick (in any gear) Suspension F: Kayaba telescopic forks R: Kayaba shocks/swing arm Transmission S speed constant mesh coupled to wet multi-disc clutch Seat height 32 in. Ground Clearance .. : 7 in. Wheelbase: _ ...• _ 55.S in. HP with Silencer 38 ft/lb @ 5500 RPM Torque" '" _37 ftllb @ SOOO RPM Dry Weight 197 lb., prototype: 215 lb., production KAWASAKI 250 FIGURES (Designated F-11M in production) Engine 247cc two-stroke piston-port single 68mm x 68mm Bore x Stroke Compression Ratio 8: 1 Ignition Magneto COl Starting Primary kick (in any gear) Transmission _ 5 speed constant mesh coupled to wet multi-disc clutch Carburetion _.........•..34mm Mikuni Suspension F: Kayaba telescopic forks R.: Kayaba shocks/swing arm Wheelbase _ _ SS in. Seat Height .............•..............................30.5 in. HP with Silencer ..............•.................. 30 @ 7500 RPM Torque with Silencer 21.5 ft/lb @ 6500 RPM Dry Weight _ 182 lb., prototype: 207 lb., production 250 and 450 PROTOTYPE Molocrossers more than strictly necessary. Both the 450 and the 250 are quiet by off-road racer standards with the silencer welded on to the expansion chamber on the 450 and a Skyway damped on the 250. 250 PROTOTYPE The 250 Kawasaki prototype that Peter Lamppu rode in the TransAMA Support class is powered by a breathed-on version of the 246cc F -11 engine. Ports and port timing are altered and a 34mm Mikuni is used. The head may be reworked but, all in all, it is basically the standard 250 production engine. The motor is carried in a frame that is similar in configuration but differen t in dimensions, geome try and feel from the 450 frame. Some of the older double downtl!.be frames, which are really slightly changed stock items, are still being used but will not appear on the production 250 and were not tested. The frame and seat combine to put the rider quite a bit lower to the ground and the ground clearance is down to a shade under seven inches. The wheelbase of the 250 is sligh tly shorter but even with the shorter wheelbase, it is more directionally stable through and Please turn to P. 69 Another National champion, Masaharu Takezawa of Japan, tries to lower his lap times on the 250 prototype. His usual berser:k style is smoothed--out on this corner. I' I' I I I•