Hail the new king of real-world, all-around 600s. Kawasaki has unseated the Honda-again, by a credit-card-thin margin-by doing much of what the F4 does well, only a little bit better. Take that glorious chunk of engine. It's every bit and more the Honda's match for refinement, with superb throttle response, not a hint of cold-bloodedness and a silken nature that makes you think every moving part has been obsessively pared and balanced. Plus, the thing emits a grin-inducing growl under acceleration that no other bike here can hope to emulate.
Although the 6R feels happier snarling around a couple of grand higher than the Honda, it doesn't need that kind of treatment to make good headway. It's just that sound...how can you resist? You're never aware of having to spin the ZX-6R hard, only of a seamless supply of power that moves the bike down the road with sublime ease. Its nondramatic transition from midrange to top-end yowl reminds us a bit of the Honda, but the 6R winds up quicker and seems much more at home with the tach needle brushing the redline. Down in the drivetrain it's more good news, with the Kawasaki possessing a light-action gearbox with perfectly selected ratios (albeit a bit shorter than the Honda's) and very little lash.
Kawasaki lavished as much attention on the ZX-6R's chassis this year as it did on the engine, with similarly good results. Although the bike feels soft compared with the Suzuki or Yamaha, it's very close to the Honda in terms of feel and back-road capabilities. With a slightly wider seat/tank interface, the 6R initially feels bulkier than the Honda (and particularly chunkier than the svelte Yamaha), but the impression fades as you attack the curves. Kawasaki redistributed the 6R's weight a bit but the bike retains its light steering (lowest effort of these four, but a touch heavier than the Triumph's) and willingness to transition quickly. Here's another one, along with the Honda, on which you could make good time sitting flat-assed on the seat.
We increased damping levels on the 6R's front and rear suspension from the baseline (up to about two-thirds of maximum compression damping and three-quarters of max rebound) to help settle the ride a bit. Our faster and heavier testers noted the 6R's tendency to feel a bit loose over rough pavement and after especially violent transitions. (This was most noticeable coming off the Yamaha or Suzuki, and less so after riding the CBR.) All else being equal, the Kawasaki moved around on its suspension slightly more than the CBR, but this motion never resulted in the chassis doing anything untoward.
Give the Honda a quarter-point advantage in suspension development, then, and trade it back for the Kawasaki's superior brakes. The six-piston fronts feel hugely improved over last year and are nearly the equal of the Yamaha's class-leading components but a significant step ahead of the Honda's or Suzuki's.
Trading points like this continues until you start counting for commuting and touring. Here the Kawasaki pulls ahead with the smoothest engine in 600-land, large, clear mirrors, handsome instruments with a clock you can see all the time and perfectly rational ergonomics. The ZX-6R's bars are the slightest bit lower than the CBR's but you've got more legroom. Seats compare favorably, though some riders complained that the Kaw's forward tilt pushed them against the tank too boldly.
In the end, we decided the Honda and the Kawasaki traded punches across the categories almost to a tie. But we're suckers for personality, and it's the 6R's rev-happy engine and aggressive appearance (some would say outlandish) that put its jutting-lip ram-air snout an inch or so ahead of the Honda's more feline countenance.