Supersports: Kawasaki Ninja ZX-6R vs. Suzuki GSX-R600 - Comparison Test

Why only two 600s, you ask? Because the new-for-2009 Kawasaki ZX-6R prevailed in that year’s crotch-rocket comparo, and the Honda CBR600RR and Yamaha YZF-R6 haven’t received serious engineering attention in the meantime. Why should they? These bikes are expensive to develop, and sales in the 600cc class have been about as lively as a Bourbon Street Fat Tuesday AA meeting.

A neckful of beads, then, to Suzuki for building a new 600 anyway (while it was already building the nearly identical GSX-R750). Suzuki says the engine is all-new, but its 67.0 x 42.5mm bore and stroke are same as before (numbers it shares with all three other Japanese 600s). Brand-new the Gixxer may be, but the CW dyno shows more or less the same horses and foot-pounds as before: 103.3 hp and 44.2 ft.-lb. Suzuki specs say compression is bumped a tenth to 12.9:1; Kawasaki compression is 13.3:1.

While the two little beasts wail pretty much in lockstep from low rpm toward their 13,500-plus power peaks, at 12,000 rpm the curves diverge: The Kawasaki takes off and leaves the Suzuki behind, culminating in an astronomical-for-a-600 112 horses at 13,770 rpm (our 2009 ZX-6R made 110 hp). Hold that gear longer if you need to: Both motors will overrev to about 15,000 rpm before the limiters cut in.

Other big changes to the GSX-R include the switch to a Showa Big Piston Fork (like the one on the Kawasaki), armed with radial-mount Brembo four-piston brake calipers—just like big-bro GSX-R750. The biggest improvement comes in the form of a 20-pound weight reduction, all the way down to 387 pounds without fuel—12 whole pounds lighter than the ZX-6R.

Light weight and high cornering speed are the hallmarks of the 600cc class. If you happen to be a pro-caliber pavement rider, you're in for a treat (or so Cernicky and Canet tell me). Not only did Cernicky turn his third-fastest time of all nine bikes in this sportbike comparofest using the ZX-6R (in spite of its being as much as 19 mph slower in terminal speed at the end of the long straight), in the end he found it the most satisfying to ride. "Everything is so acute on this bike, you have to be so precise, I wish my leathers fit better. Every tiny movement has consequences," said Cernicky, whose best time on the Kawasaki was 1:54.65. It's not just that the 600s weigh less than the others, it's also that the reduced spinning crankshaft mass makes them capable of really quick direction changes, very important on this mostly tight, technical track.

The same comments apply almost but not quite equally to the GSX-R, upon which our crusty crusader turned a best lap of 1:55.72. Not only does the ZX-6R have a 9-hp advantage up top, it’s also geared a tad shorter than the GSX-R, which lets it get its tach needle into the powerband sooner. And its biggest advantage over the GSX-R may have been the presence of Kawasaki’s testing-support team of Joey Lombardo and Jeff Herzog to make sure the bike was set up perfectly (Suzuki did not attend).

Trail-braking into corners on the Kawasaki, Cernicky said he could feel individual rubber molecules deforming and shearing. That's some tasty front-end feel there (a thing none of the heavier bikes can match). The GSX-R was a tick behind the ZX-6R, with slightly less front-end feedback, and it didn't feel as planted, although its ability to change direction midcorner was fantastic. Outright braking performance was just about equal, and not one person complained about the binders on either machine.

For the 98 percent of us not quite so gifted as Cernicky in the speed and traction-detection departments, the 600 experience can be less gratifying: Speaking for myself, corner entry speed is set less by tire grip than by the internal Oh-$#@%! meter, and it's going to take more than two days riding around a technical track like Inde before yours truly is going to be diving into blind corners at the speeds these 600s are capable of (in fact, it might take more than two lifetimes, given my history). If you find yourself wanting more speed after the apex on a bigger bike (especially one with TC), you twist the throttle and pick some up. On the 600s, if you're slow going in, you're slow coming out, too. Try to do better next lap.

In theory, this leads to better riding, and if you’re on the upslope of your roadracing career, the 600s are great trainers. Case in point, our own Off-Road Editor, Ryan Dudek, a pro-level off-roader and Catalina GP winner making a rare appearance on a paved circuit: Day two of our Inde test marked his fifth-ever day of track-star knoblessness. That lack of experience didn’t keep the Duder from riding around the outside of me in one right-hander on a 600 (I was on my out lap!), and at the end of the day, he ran a 2:07.6 on the GSX-R600 and a 2:04.3 on the ZX-6R. Slightly apprehensive, he really didn’t want to ride the ZX-10R, but I insisted, for the sake of science: Three laps later, swaddled in the TC2 safety blankie, Dudek let his roosting instinct take over and the kid reeled off a few laps in the low 2:00s.

Though the 600s can be challenging to use truly as intended on the track, they’re a blast to ride on the street, a place where both these bikes feel plenty fast. Their engines aren’t exactly peaky, but they do crave revs, and it’s progressively addictive to feed them; especially the GSX-R,which has a tuned intake system (like the 750’s) that gives it a truly classically raspy four-cylinder soundtrack, which means you wind up riding it faster than you would a liter bike just to hear it sing. And if you haven’t ridden a 600 lately, you’ll also be amazed that you can whisper along on both of these at 25 mph in top cog through beach traffic, no problem; the dichotomous Jekyll/Hyde nature of the things is a true engineering marvel.

The GSX-R gets three-way adjustable footpegs and its bars are a bit lower in relation to the seat. Springs are what you ought to expect if you buy a bike whose chief weapon is cornering speed: Both bikes are firm, but at least the attending damping is really nice. And those seats aren't designed for touring, either. In their defense, all I can say is my aging back hurts more when I don't ride bikes like these a few times a month; they provide a good yoga-style stretching, and you will use your legs and torso for support.

At the end of the day, if it’s the pure racer-with-lights experience you’re after (not to be confused with the fastest way around the track unless you’re a pro), the 600 class is the place to shop, particularly the shop with the Kawasaki sign out front.