The ZX enters the Track portion of our test on the heels of a victory in the street portion of our Supersport shootout. It had the extra cubes, a slipper clutch, and a revised chassis, but can it complete the sweep?
The Zixxer has had a motor advantage ever since it debuted with its “cheater” motor in 2003, but its overall rankings were held back by a chassis that didn’t feel as sorted as its competition. Now with this new iteration, there’s nothing aside from a silly tachometer that holds it back.
In years past, bikes like the R6 and CBR were heralded for their natural and rider-friendly characteristics, and the ZX-6R now joins that club. Our testers raved about the ZX’s radical improvement in rider comfort and neutral handling. Its roomy cockpit gives a rider several body-position options, and a change to more conservative steering geometry endows the Kaw with a less skittery and more confidence-inspiring ride.
My first session at Infineon was on the ZX, and I came back muttering to myself that this bike surely must be the winner. Unlike the previous version that took some cojones to extract its best, this new one is entirely cooperative.
“It’s a night-and-day improvement over last year’s bike in every way,” reveals Roberti after his first stint. “Its chassis is very solid and it handles bumps on the track very well.”
Kawasaki relaxed the ZX’s rake and added stability-inducing trail for ’05, but the chassis still responds rapidly to steering inputs thanks in part to the leverage provided by the wide-set clip-ons.
“The bike was a little slower on turn-in compared to the CBR and R6, but made up for it with stability and how it holds a line,” Becklin relates, adding, “I might lower the front (for quicker responses) just a bit if it were my bike.”
Lowering the front end, though, would steepen the rake and lessen the trail, which might make the mad Kaw a bit too nervous. As it is, the ZX’s class-leading power can induce some headshake with the race-compound Dunlops spooned on. Its motor pulls the hardest, so it’s more prone to wagging its head.
“This was most noticeable at Thunderhill in between turns 1 and 2,” explains BC. “The ZX pulls so hard coming over the rise that the front end is very light, and it sometimes resulted in some pretty nervous clip-ons.” It should be said here that the R6 and CBR also exhibited mild headshake on the race rubber, and we’d recommend a steering damper for those who spend a lot of time at the track.
While the roomier riding position gives more options for riders of various sizes, a few of our testers believed it also made the ZX feel bigger and longer than the others. “Ergonomically,” says BC, “the bike is vastly improved, but it is not quite as aggressive as the CBR and R6. While this helped its score on the street, I feel it hurts it on the track.”
With a radial-pump master cylinder and radial-mount 4-piston calipers, the ZX has the braking power to match its impressive acceleration.
With an extra 37cc, it’s no surprise that the ZX is nearly in a class by itself in terms of outright power. At Infineon, we had fun getting hard on the gas at the exit of the carousel, hastily accelerating fast enough to pull past Ducatis and RC51s on the following straight. The ZX squirts out of corners almost like a 750, easily leaving bikes like the CBR in its dust. And unlike the Honda and Yamaha, the ZX has very smooth throttle response.
“The motor is hands-down the best in the class,” says the surprisingly talkative Chamberlain, before noting that the ZX can’t be raced in most 600cc competitions. “It pulls considerably harder exiting corners and continues pulling hard all the way to redline.”
As if the extra cubes weren’t enough to separate the ZX from this group, it also comes with another tool exclusive to this quartet: a slipper clutch. Borrowed from last year’s race-spec ZX-6RR, the back-torque-limiting device was nearly as dominant in pit-side conversations as the mega motor. The trick clutch aids not only multiple downshifts when braking, but it also lessens lower-speed off-throttle abruptness.
“One of the biggest highlights for me is the slipper clutch,” says BC, a Yamaha TZ250 owner that appreciates a lack of compression braking. “Now, even the laziest, most unskilleddownshifter can still enter the corner smooth as silk.”
Basically, a slipper clutch lets the rear wheel roll more freely when the engine is compression braking, so a poorly timed downshift won’t result in a hopping or chattering tire. It simply makes sport riding easier. We said it in our street test, but it’s worth mentioning again: One day all sportbikes will have some form of slipper clutch, and Kawasaki leads the way in this class.
“The strong motor and ability to confidently bang downshifts using the slipper clutch means it’s easy to get the bike into a gear that pulls out of the corner,” Becklin notes.
The Zixxer shines in other areas, too, boasting some other unique features. Its brakes are perhaps the best in this tough crowd its system of a radial-pump master cylinder and radial-mount 4-piston calipers are not exclusive to the ZX, but its 300mm petal-style rotors and higher-spec 4-pad-per-caliper arrangement is. These killer binders are powerful and easy to modulate, and speed retardation is assisted by the slick slipper clutch.
Ken seemed to dig the ZX motor, but there’s more to track riding than just having a mondo-powered bike beneath you.
We should also note that the ZX’s new Showa suspension works much better than the Kayaba dampers on the old bike. Once we adjusted to the bike to accommodate the race rubber, we never felt a need to fiddle with its settings. Then at Thunderhill, a much bumpier track, we took out a half-turn of front compression damping and were able to leave it alone the rest of the day. “It seems impressive to me that the bike was set up early and worked well all day,” says Becklin.
Like a pimple on the nose of a supermodel, the ZX-6R‘s glaring wart is its unintelligible tachometer. A progression of lights sweeps around the digital speedometer, but its LCD display is nearly impossible to read at a glance in daylight. Some of us didn’t care much, relying instead on its shift light, but others found it inexcusable.
“The tach is even more of a hindrance on the track than on the street,” says BC. “On the street you are usually shifting by feel and usually shifting far below redline, but on the track where you can actually rev the bike out, it would be nice to see where you are at in the rpm range.”
– On-board stopwatch.
– Decent gearbox, but not as cooperative at the GSX-R’s and CBR’s.
– Refined feel: “Kawasaki did a very good job in the detail department. Nothing vibrates or rattles and it feels well put together.” Becklin
– Lighter, #520 chain and sprockets.
– Windscreen too low and swept back for some riders. “You’d have to be a pygmy with a shrunken head to get behind that thing.” Becklin