ZX-6R
It's fair to say that Kawasaki invented the modern 600 supersport bike: its GPZ600R appeared a year after the 900, and while not a full Ninja, it introduced the 16-valve, water-cooled DOHC motor to the 600 class. The GPZ was replaced by the GPX600R in 1988, before the super-soft touring ZZR600 appeared in 1990. The ZZR had an awesome engine, and was the fastest 600, no question, with a 150 mph top end. But it was fat, soggy, and no match for the opposition on track (although it enjoyed some race success in the UK).
So Kawasaki applied its Ninja formula to the 600 class for 1995, putting an all-new 599cc inline four engine into an aluminum frame with sharp-styling. With its ram-air intakes and garish paint schemes it was an extrovert's dream machine, and had performance to match.
Updates through the rest of the decade kept the ZX-6R in touch with the rest of the class, although Honda's CBR remained at the top of the heap.
By 2002 though, Kawasaki's 600 supersport bike had lost its way, and the firm needed to do something radical. Which it did - and how! Whether you call it lateral thinking or sheer desperation, a team of Kawasaki engineers simply gave their lackluster engine a big-bore treatment, increasing the capacity to 636cc. Instantly, the ZX-6R gained a definite edge over the opposition: peak power was still in the ballpark, but the midrange on the mini-Ninja was fat and grunty. Like a wild hog, the 636 lumbered ahead of the peaky 599cc opposition, and when Kawasaki added fuel injection a big weight loss program and a serious restyling package for 2004-its bike was the 600 to have.
Kawasaki went back to a 599cc motor for 2007, and while it had caught up sufficiently in the tech specs to match the competition once more, most folks missed the zing that came from those 37 extra cubic centimeters.
The brakes were good for the time (appalling now), suspension was comfort-soft, and for blasting across continents two-up little could touch it. Twisty canyon roads confounded the chassis however, and Honda's 1992 CBR900RR consigned the ZX-11 to sport-touring status. But even today that engine still makes for a beguiling adrenaline hit.
ZX-7R
In the late 1980s and early 90s, the 750cc class was much more important than it is now. Liter class bikes were a bit too fat in the ass to offer much in the way of fine handling, and the superbike class in both world and national level racing used a 750cc inline-four formula. As a result, all the Japanese firms were making supersport 750s - a class invented by Suzuki with its 1985 GSX-R750.
Suzuki may have invented the three-quarter liter class, but Kawasaki sure as hell made a big splash. Its first attempt was the ZXR750 H1 launched in 1989 - and it looked like it had come straight from a world endurance racetrack. Styled like the firm's ZXR-7 endurance racer, the bike had a tuned version of the GPX750 roadbike engine mounted in a race-replica aluminum beam frame with full race fairing, and top-spec suspension and brakes. Two "hoover pipe" air ducts arced back from the top fairing into the fuel tank, feeding fresh air to help cool the cylinder head. It made 105 HP, weighed 420 pounds, and was an instant hit mostly due to its super-hard styling and great track handling.
The ZX-7R developed over the next seven years, gaining power and sophistication before it was heavily updated in 1996. That version gained about 20 HP over the original and lost a couple of pounds. And like the original, it was an instant cult classic, thanks again to the awesome styling and strong handling, especially the super-communicative front end.
ZX-11
It was the early 1990s and liter class bikes meant big power and big speed. None came with more of both than the ZX-11. The big 11 was a simple package: massive, super-strong 1052cc engine putting out 145 HP in an aluminum frame with a very slippery fairing. That bodywork helped the ZX-11 gain the title of 'world's fastest bike,' and it held that title until Honda's CBR1100XX Super Blackbird was launched in 1996.
ZX-9R
Back in 1992, Kawasaki (like all the other Japanese firms) was left holding a knife in a gun fight. Honda's CBR900RR was 50 pounds lighter than Kawasaki's ZX-7R and put out more power. Kawasaki's big-bore sportbike, the ZX-11, was extremely fast, but couldn't come anywhere near the 900RR in handling. Surely Kawasaki could come up with a 900cc version of the ZX-7R in quick order?
Well, yes was the answer. But, sadly, the first ZX-9R owed much more to the supertanker ZX-11 than the track-blasting ZX-7R. The 125 HP engine was almost as powerful as the ZX-11's, but the bike was far too heavy at 470 pounds dry.
Various updates over the next nine years saw big improvements in the ZX-9R. The final version put out 141 HP and weighed a touch over 400 pounds. It was still left far behind by the latest generation of liter bikes though: The Suzuki GSX-R1000, Honda CBR954RR and Yamaha R1 made the Kawasaki a poor choice for outright performance.