Kawasaki's ZX-6R: Sharper blade for the Ninja

By Denny Thrush, photos by Kevin Wing and Riles and Nelson

It had been ages since the last time I rode a 600cc sportbike. The temperature was a tire-hardening 30 degrees, even before factoring in fifth-gear windchill, and there was the added uncertainty of not knowing when AMA Superbike rider Roger Lee Hayden or World Superbike pilot Akira Yanagawa was going to blow by.

And you know the best part? I was totally comfortable.

Well, maybe not comfortable with the temperature of my hands, but I did feel completely comfortable on the new 2007 Kawasaki ZX-6R Ninja, despite the less-than-perfect conditions at Barber Motorsports Park for testing a racer replica.

And in no way is that damning with faint praise. This is one sweet sportbike.

Kawasaki has completely redesigned the 600-class Ninja for 2007 and made some surprising changes of strategy along the way. Gone is the 636cc version that compared favorably to its 600cc competitors because of the extra torque from its displacement advantage. Instead, Kawasaki has returned to the Supersport racing-based formula of a 600cc inline four-cylinder.

That made Kawasaki's job harder. Not only did the 2007 Ninja have to have enough midrange to compare to its 636cc predecessor, but it also meant Kawasaki wouldn't have a separate model, like it did with the 2006 ZX-6RR, to serve as the basis for its AMA Supersport racebike. The pressure was on to come up with a single motorcycle that could fill both roles, so Kawasaki did the first clean-sheet complete redesign of its 600cc powerplant in 10 years, along with an all-new chassis.

The result, in the form of the new ZX-6R, is a bike that worked great on the Barber Motorsports track but will also be a darn good streetbike, I believe.

Start with the ergonomics. The clip-ons are low, but not uncomfortable by sportbike standards, and legroom is ample. Even other writers over six feet tall found they weren't folded up uncomfortably, despite the bike's compact dimensions.

The seat also offers more comfort than the typical racer-replica saddle and gave me plenty of room to move around whether hanging off in the corners or edging forwards or backwards under acceleration or braking. The gas tank is tapered to be especially slim between the rider's knees.

The ZX-6R gauge package is unobstructed, easy to read and gives the rider just what he needs. The white-faced tachometer positions the 16,500 rpm redline just about the 12 o'clock position, making it easy to see at a glance when it's time to toe the next gear. Inset into the tach is a digital gear indicator, a nice touch. To the right is the digital speedometer, odometer and other readouts.

When it's time to pull onto the track, the Kawasaki crew pulls off the tire warmers. Did I mention it was cold?

Given the conditions, I rode the first sessions at a reduced pace to get used to the resurfaced track and the Bridgestone tires before pushing too hard. That's when I learned that Kawasaki succeeded in reproducing the old 636's midrange in its new 600.

Despite sometimes running a gear higher than I normally would, the Ninja pulled smoothly and strongly, even down at 5,000 rpm, where I usually wouldn't be riding on the track. That strong midrange in a 600cc package is a good sign that the Ninja will make a versatile streetbike, despite its trackday focus. Sure, 16,000 rpm is fun, but you don't have to be pegged against the redline to get performance out of this 600.

The Kawasaki engineers had a disassembled engine on display for us, and it's easy to see why the new powerplant is so willing to rev. Some parts, particularly the connecting rods, look impossibly small and light. By designing everything new from the ground up, Kawasaki came up with an engine that's more compact, lighter and more powerful. The cooling system, including the liquid-cooled oil cooler, was also upgraded, not that we needed that improvement during our Alabama cold snap.

What revs up, must slow down. And as I find when I downshift into Barber's turns, Kawasaki's back-torque-limiting clutch makes everyone look like a better rider. In several riding sessions over parts of two days, even in sketchy traction conditions caused by cold temperatures, I never once locked up the rear or even experienced any wheel hop.

Here's the bottom line on a good slipper clutch like Kawasaki's: It lets you cross one more thing off your list of worries. That's a big advantage when you're braking, downshifting, positioning your body for the rapidly approaching turn, and doing all of that at the fastest speed you can handle. Not having to be perfect about coordinating your downshifts, throttle blips and engine speed just allows you to focus on the other lifesaving tasks at hand and makes you smoother. And good riding is always about being smoother.

The cassette-style six-speed transmission was also flawless. I rode several different bikes, and one of them was a bit balky on upshifts, but the rest were perfect. I never hit a false neutral in nearly two days on the track.

As good as the powertrain is, it's not the strong point of the new Ninja. That has to go to the handling.

Kawasaki said the goal of the redesigned aluminum chassis and new suspension is to let the rider keep the throttle open. To do that, they tuned the flex of the chassis to soak up bumps in the track, and they did it without muffling feedback.

Riding around Barber, which has a few bumps of its own, the word that kept coming to my mind was "forgiving." That may seem strange for a sportbike with stiff, racing-oriented suspension, but that's the way it felt. If I hit a bumpy patch or needed to change lines in the middle of a turn, the bike didn't get unsettled. And despite not wearing a steering damper, like its big-brother ZX-10R, the 6R never once wagged its head.

The result was that I was instantly comfortable. So comfortable that before long, despite the temperatures — did I mention it was cold? — I was touching down the footpegs.

The Kawasaki technicians dialed in some additional preload for me on the rear shock, which had the effect of raising the rear ride height 15mm. That small change not only stopped the pegs from kissing the asphalt but also made the sweet-handling Ninja turn in even faster. I just wish I'd made the adjustment sooner.

Two other pieces of evidence show just how good the Kawasaki's suspension was working.

One, even though the suspension was dialed in specifically for Barber, the settings were very close to the way they are when the bike leaves the factory. Also, as riders swapped back and forth among several bikes, most found that the suspension worked well for them even without changing the settings, despite the fact that they ranged from maybe 160 pounds to well over 200 pounds.

The second piece of evidence came from the comparison of how the Kawasaki handled on the stock Bridgestone street tires and DOT race tires, like the ones used in AMA Supersport racing. Stickier tires can reveal handling flaws in some bikes. In this case, the race tires just made the Ninja steer even better.

Power, handling — the last piece of the performance puzzle is the brakes. The twin petal rotors on the front of the ZX-6R provide all the stopping power you'd expect for a bike built for the track. Feathering the lever with two fingers provided all the feedback and power I needed.

Really, I'm having a hard time finding something about this bike that I don't like. I know some riders aren't thrilled about the styling of the front view of Kawasaki's latest sportbikes. More than most of its competitors, Kawasaki has focused on aerodynamics. The 2007 ZX-6R gets an even more compact ram air intake in the center of the fairing and the small projector headlights that look beady-eyed to some. But it adds up to less frontal area and less aerodynamic drag.

Come to think of it, that was one thing I didn't enjoy. That reduced frontal area contributed to me freezing my kneepucks off.

Did I mention it was cold?