Kawasaki Z1-R ; The Answer to a Challenge from Honda

King of the Road – Kawasaki Z1-R

In the late ‘sixties, Japanese motorcycles were either small two strokes or similar sized bikes from suck-squeeze-bang-blow devotees Honda. The first hint that things were about to change came in late 1968 with the announcement of the Honda 750 four. At first, the competition stuck with their two-strokes: Kawasaki’s H1 and H2 triples and Suzuki’s Titan and GT750, while Yamaha grabbed a toehold in the big bike market with its XS650 twin.

Kawasaki was first to drop the other shoe. It’s widely reported that the K-men were working on their own SOHC 750 four when they heard about the new Honda. The design brief was altered to leapfrog Honda with an extra camshaft and another 150cc.

Though the 903cc Kawasaki Z1-R was four years behind the Honda, it had so much more performance that it created at least as much fuss. With around 82hp (compared with Honda’s 60 or so), it was easily the fastest bike on the road, capable of 210kph. And it was also faster than its frame and cycle parts, as many early pilots found out. The mild steel double cradle frame lacked rigidity, the 36mm forks were under-specified, and the rear suspension over-sprung and underdamped. In order to avoid a heavy steering feel, engineers also gave the Kawasaki Z1-R a sharpish 26 degree steering rake. Sudden changes of direction, encouraged by the quick steering, would induce weaves, which a few bumps could turn into a tank-slapper as the back wheel tried to catch the front. Neither was the single disc/drum brake combo up to hauling 240kg of motorcycle down from 200-plus kph.

Nonetheless, the Z1 was firmly established as the gold standard in the superbike category, a position it held until 1977 when the Suzuki GS750 arrived. Kawasaki responded with the KZ1000; and in 1978, when the Yamaha XS1100, Suzuki GS1000 and Honda CBX also joined the party, they produced the Z1-R.

Radical Departure

In fact, the Z-bike had seen relatively little development since its introduction. A second front brake disc was added in 1976 together with the designation Z900. The 903cc Z1 engine was stretched to 1016cc in 1977 by increasing the bore from 66 to 70mm to create the KZ1000—though claimed power output from the mille motor was still 82hp using 26mm Mikunis and a four-into-two exhaust. The KZ frame was beefed up, but it still lacked core rigidity.

Perhaps because they were working with essentially a six-year-old motorcycle, Kawasaki chose to emphasize styling in creating the Kawasaki Z1-R. And while BMW and Ducati were first to fit factory fairings on the 1974 R90S and 750SS, Kawasaki’s handlebar-mounted item on the Z1-R was the first on a mass-market Japanese bike. Its squared-off lines echoed the 13-litre “coffin” gas tank, triangular side panels and swooping tailpiece, all finished in ice-blue metallic paint.

The same KZ1000 engine (but with 28mm carbs) went into the same flex∆y frame, and was hooked to a racy four-into-one exhaust. Claimed horsepower was up to 90 at the crank (though period dyno tests failed to find much more than the stock KZ). New cast alloy wheels were 18-inch front and rear, and drilled triple discs handled stopping the now 260kg-at-the-curb missile.

The Kawasaki Z1-R’s radical (for the time) styling was a big hit, with the color especially causing something of a stir. Punters either loved it or hated it, but almost no one was indifferent.

It was when reviewers actually rode the Kawasaki Z1-R that the wheels started to come off—off the ground, anyway. As well as using essentially the same frame, though with extra stiffening gussets, as the earlier, lighter Z1, Kawasaki fitted new alloy wheels, and the front 18-incher reduced the already scant trail even more, making the R version livelier still than its predecessor. Together with stiffer rear springs and increased damping, “it doesn’t roll over bumps: it bounces from crest to crest,” wrote Cycle Guide. The same magazine found the handling “less than roadracer precise thanks to numerous rubbery frame tubes,” and also criticized the suspension, which “makes the Kawasaki ride harshly on the flat and lets it wobble in fast turns.”

Kawasaki Z1-R Revisited

Chastened perhaps, Kawasaki dropped the Z1-R for 1979 before returning in 1980 with a significantly revised version that seemed to meet much of the criticism leveled at the ’78 model. Gone was the metallic silver blue paint and four-into-one exhaust system, and the frame had been tossed in the dumpster. Replacing it was the new, stiffer chassis with double-walled down tubes from the 1979 KZ1000 “MkII.” The penalty was a weight increase to 251kg dry.

The new frame, together with a 19” front wheel and reduced offset in the triple clamps, increased trail from 84mm to 100mm. Gone were the wobbles, harsh ride and choppy handling of the ’78, though the new bike still compared less than favorably with the GS1000S in this respect, according to period reports. In the engine, a new, heavier crankshaft with revised balance factor reduced vibration, but the overall specification remained the same. A more practical 17-litre gas tank replaced the 13-litre item from 1978, and a more comfortable seat increased the rider’s range to match that of the bike.

Other detail changes included V-rated tires, an extra two teeth on the rear sprocket and improved ground clearance. The finish was any color you wanted, as long as…

One curious feature was the front brake operation, achieved via a cable leading fro$m the lever to a remote master cylinder. This gave an indirect feel to the lever which was both panned (as being vague) and praised for moderating the front brake’s “wooden” feel. Overall, though, reviewers still found the GS1000S quicker on the track, though the Kawasaki Z1-R’s new lower gearing meant it was quicker through the trap.

The Z1-R had grown up: Kawasaki’s engineers had tamed the beast so it would still do the business when the tree lights turned green but was far less likely to bite you in the bends. Much of this development went into the green team’s AMA racing challenge in 1981, when one Eddie Lawson ended the season in first place. In celebration, Kawasaki produced one of the most evocative bikes of the era, the KZ1000R Eddie Lawson Replica. But that’s another story for another day.

– Robert Smith, December 2010 (issue #267)

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Kawasaki Z1-R – The Answer to The CB750 Challenge

Kawasaki Z1-R Revisited

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