THE WORLD’S GREATEST BIKES #10 KAWASAKI ZXR750
In a grid full of expensive exotics, this was the WSBK winner for every man
Remembering the glory years of the World Superbike championship, thoughts turn to the ultra-exotic money-no-object homologation specials such as Honda’s RC30 or RC45, Yamaha’s YZF-R7 or Ducati’s stable of thoroughbreds. But one bike bucked this trend and, with the help of an American tuning house and one of the most determined riders ever, took on and defeated the world’s best. When the Kawasaki ZXR750 claimed the 1993 title it was a victory for the working man’s superbike. And it all started with the ZXR750 H1 (and later H2).
Launched in 1989, the ZXR750 H1 was developed and tested during the 1988 World Endurance series. Much like Honda had done with their exotic RVF750 as it evolved into the RC30, Kawasaki took their existing superbike as a base and built a prototype racer around it. In the case of the Kawasaki, it was the GPX750 that became the ZXR-7 race bike and finally the ZXR750 H1.
Taking the GPX’s inline-four engine, Kawasaki made some fairly radical mods which nowadays might seem somewhat of a backwards step. Where the GPX ran a rocker arm valve train, the ZXR-7 reverted to a bucket and shim-style. Kawasaki took this decision to allow the ZXR to rev higher in race trim as tech at the time determined this as the best route to power. In road trim riders would have struggled to spot the change as the ZXR only made 1bhp more than the
GPX with identical torque but it did gain a lighter crank, revised timing, semi flat-slide carbs and Kawasaki’s new Back Torque Limiter slipper clutch. The chassis, meanwhile, was a completely different story.
As World Endurance rules allowed prototype chassis, Kawasaki threw away the GPX’s steel double cradle frame and developed a new aluminium beam chassis with a tubular under cradle. Dubbed the E-Box frame (which many joked stood for egg-box) it comprised aluminium beams connected to a cast headstock and hollow swingarm pivot structure braced with alloy ribs. Although 2.7kg heavier than the GPX’s frame, it was more rigid, allowed for a bigger 6.4-litre airbox, and featured inverted forks and 17in wheels, making the ZXR the first Kawasaki to have such a set-up. This was quite radical as there weren’t many 17in road tyres available (the OE Bridgestones were notoriously poor) with most rivals running 18in rears and 16in fronts – but Kawasaki knew where they were focusing the ZXR and with race bikes running 17in wheels, the ZXR had to as well. And that wasn’t the only trackbased addition.
Copying the ZXR-7’s boxy-look, the ZXR750 gained the endurance racer’s ‘Hoover pipes’. A standout design, on the racer they fed a forced airbox but on the road bike they simply channelled cold air onto the top of the cylinder head with few, if any, performance gains. Unless you are talking car park performance, in which case they added about 40mph to the ZXR’s perceived top speed.
When it was released in 1989, the ZXR750 H1 was a bolt from the blue. The chassis was staggeringly good on road and track. Plus the styling, especially in the enduranceinspired green/white/blue with green wheels, was nothing short of jaw-dropping. But the ZXR750’s heritage will always be the fact it was the superbike that the working man could afford to buy, ride to Brands Hatch and then cheer the same bike on as it did battle on track against machines that cost twice times as much in showrooms… and watch it win! Yes, being patriotic we all cheered on Foggy, but the ZXR750 was the underdog that epitomised the spirit of WSBK – production racers that you could have in your garage – and that’s why we all loved it. And still do.