Kawasaki F9 story

Kawasaki’s two-stroke 350cc series of trail bikes starts at the end of the 1960s when the company realised that serious riders were after more power on the dirt. Having had trail irons on sale in the USA for several years, the 350 was always going to happen but, arguably, the launch of Yamaha’s RT-1 360 focussed the Kawasaki R&D team’s minds. For the 1970 model year the F5, aka Bighorn, was launched and looking remarkably similar to the 250 F4 Sidewinder, which had been developed from the F21M moto crosser. The F5 differed from its 250 relative by having a conventional five-speed gearbox rather that the rotary, ‘one more tap and back to first from top’ style transmission. The all new F5 only ran for two years before Kawasaki decided to carry out a root-and-branch re-design, which would deliver the F9 ready for the 1972 model year. Both the F5 and F9 featured discvalve two-stroke single engines, yet the latter model was apparently offered less power, on paper at least. Where the F5 had been quoted as delivering 33bhp, the later F9 was only turning out 28 horses. Certain models of both the F5 and F9 appear to have featured the legendary Hatta frontend. These forks allowed the rider to alter rake, trail, spring tension and fork length to specific riding conditions. The most obvious feature of the forks was the lower legs, which ran two axle mounting holes. By simply dropping out the wheel and swivelling the legs 180 degrees, riders were immediately able to access three positions for the axle: behind the fork centre, in line with it or ahead of it, which instantly changed the trail dimensions. The F9 enjoyed a four-year model life before it was axed in 1975. Two-strokes had had their day and bowed out to environmental pressures. Interestingly, it was Kawasaki’s intention that the Bighorn should be an all-round, do-anything bike, but it’s debatable whether they ever thought the bike’s appeal would last until now. From its earliest days, the F9 acquitted itself well on dirt ovals and it’s still doing just that today in vintage racing. It’s also been the basis for numerous café racer and street tracker projects. At Bonneville in 2011 an F9 achieved AHRMA classification records for Lightweight Production (97mph) and Open Sportsman MX (109mph). Tuned engines and modified chassis have seen F9s compete successfully at WERA 500GP vintage class racing, where they regularly top 120 mph. To get an idea of just how capable the basic machine is, take look at www. klemmvintage.com/bighorntech.htm