Kawasaki Zx-6r&zx-6rr
KAWASAKI ZX-6R&ZX-6RR
RIDES 2K3
Impressive-from paper to pahrump
NICK IENATSCH
YEAH, WE KNOW Eric Bostrom and Tommy Hayden rip up the AMA Supersport series on ZX6Rs, and sure, the same bike is undefeated in AMA Prostar dragracing...but there has been something missing from recent iterations of Kawasaki’s middleweight powerhouse. Call it “trickness.”
Park last year’s ZX-6R next to Yamaha’s YZF-R6, for example, and our complaint becomes quite clear.
Kawasaki included the important main ingredients for a successful sportbike, but outward appearances didn’t convey the inward performance. A smattering of yesteryear’s boy-racer slash graphics tried to spice things up, but the bike’s style offered few outstanding innovations in a class that never stands still. In the battle of the showroom, “trickness” was an asset Kawasaki didn’t have.
All that has changed-times two! This year’s middleweight Ninja line is led by the 636cc ZX-6R and bolstered by the limited-production 599cc ZX-6RR. These brothers appear practically identical, but close perusal reveals the RR’s race-oriented goodies that provide another level of adjustment necessary to win national and World Supersport battles.
Kawasaki invited Cycle World to ride both bikes at Spring Mountain Motorsports Park in Pahrump, Nevada, with open lapping on the 6R and one session on the limited RR.
It would be a crime to focus solely on the RR’s trick bits, because both bikes flaunt some outstanding upgrades, beginning with a chassis that carries a 41mm inverted fork and radially mounted four-piston front brake calipers with four individual pads apiece working on 280mm floating rotors. Grand Prix fans will remember when radially mounted calipers debuted in 2000, with an attendant increase in not only braking power, but feel as well. Less caliper/carrier deflection means more feedback through the brake lever; that will help factory riders at Mid-Ohio and Brainerd, but it will also help you and me in a rain-soaked emergency stop. It’s absolutely thrilling to witness GP technology trickledown to a $7999 (ZX-6R) and $8399 (ZX-6RR) motorcycle. Great stuff!
The inverted Kayaba fork’s rigidity complements the radial brakes and offers three-way adjustability (compression and rebound damping, plus spring preload), as does the rear damper. Kawasaki offers 1mm shims to alter rear ride height, and has included top-out springs in both the front and rear suspension. The RR chassis goes one step farther and offers swingarm-pivot adjustability, as well as a threaded frame boss to easily accommodate a steering damper. Other notable high-points of both new Ninjas’ chassis include a removable rear subframe and an extremely direct ram-air system ducted through the steering-head area. Swingarms have been stretched for 2003, gaining length due to the reduction in size of the engine, yet keeping wheelbase in the 55-inch area.
Engine updates must begin at the intake system, because both bikes wear 38mm Keihin throttle bodies backed by sub-throttle bodies to widen the powerband and facilitate efficient low-speed operation. Motorcycle fuel-injection suffers from “digital” initial response and the sub-throttle bodies do a good job of smoothing this on-gas harshness.
These things scream, revving to 15,500 rpm, with longer connecting rods working through shorter strokes (43.8mm for the R, 42.5mm for the RR) than last year. The limited RR gets forged 67.0mm pistons weighing 5 grams less than the R’s 68.0mm cast pieces, but both bikes utilize lOmm-shorter valves than last year and trick single valve springs with oval wire that allows tighter compression from a shorter free length. The valve springs sit on stepped seats to keep them more stable, and the entire cylinder head is 10mm shorter than last year. The cylinder skirts are 5mm shorter, but the biggest change here is the rounding of the camchain tunnel, a move that strengthens the area while reducing weight, noise and vibration. During all these changes, the engineers eliminated the outboard oil lines and ducted oil headed for the cam via internal passages, and reduced the oil-pan capacity. Smaller, lighter, more powerful, and do-it-yourselfers will appreciate the simplification and change in valve-adjustment shim size to match the rest of Kawi’s line-up.
The six-speed tranny has closer ratios between the top four gears and you can change the shift-actuation spring if you want a lighter feel at the lever. That’s pretty cool and indicative of the type of tailoring we expect to become commonplace in the near future. A stainless-steel muffler leads the host of changes to the redesigned, lighter exhaust system, which incorporates a catalyzer and the KCA (Kawasaki Clean Air) system that routes fresh air to the exhaust ports.
Kawasaki wrapped the bike in what it refers to as “GPinspired” plastic, and there is an angular resemblance to the new MotoGP four-stroke. Designers resisted the urge to ruin the lines with stick-on graphics. Dual multireflector headlights and an LED taillight finish the package, and you can replace the rear seat with a nice-fitting cowling. All in all, a tightlooking, modem package.
The Ninjas also wear a modem (trendy?) digital tachometer that attempts to display rpm with a bar graph. It’s tough to read at a glance.
We lapped Spring Mountain on Bridgestone BT-012 tires, but the spec sheet lists Michelin Pilots as the stock tire. It was a cold day and the ’Stones never really reached operating temperature, but overall grip was quite good if you stayed smooth, even if feedback was limited.
My testing was assisted by a session on a lightly prepped ZX-6RR racebike wearing Dunlop’s stickiest, which helped me discern what the new Ninjas feel like on true race mbber.
Both bikes change direction magically, either at initial turnin or mid-comer. The racier riding position of the 2003 models put you in a perfect position to sense front-tire traction, and the bikes feel fantastically light and eager to try anything. This steering quickness often translates into instability, but the Ninjas were calm enough in fast transitions and highspeed sweepers to not affect the chosen line. Both bikes need steering dampers to reduce headshake when the front is unloaded over bumpy comer exits, but I’ve ridden worse.
I missed three upshifts during the day, catching false neutrals between third and fourth gears. I’ll put this down to sloppiness on my part, at least until the production Ninjas arrive at the CWoffices. The bikes rev so unbelievably high that I rarely encountered the revlimiter, but when I did, it was a soft limit that encouraged overrev and made me wonder how high these bikes will spin in race trim. I quit trying to guess what the tach was saying and went by the programmable shift light to time upshifts. Interestingly, the racebike on hand had an analog tach.. .1 suspect the digital tach would make gearing choices tough when the tuner asks you, “What rpm are you exiting Turn 3?” That said, I love the digital speedometer, and it’s nice to have a clock.
I went 1 second quicker on the RR (maybe because Tommy Elay den was lapping with me on the racebike?), but enjoyed the 636 more due to the increased midrange that translated into power wheelies out of Spring Mountain’s fifth and final turns. The 636 offered a choice of two gears in several comers because it would pull strongly in the lower midrange (7000 rpm), whereas the RR felt comparatively weak. The RR has the lighter pistons mentioned, plus a 13:1 compression ratio that is .2 higher than the 636, so the smaller engine feels just fine when the revs are up. But off the bottom, those extra 37cc can really be felt.
I didn’t take advantage of the RR’s swingarm-pivot adjustability simply because few riders this side of the AMA Superbike paddock would know or feel the difference. The included steering damper boss would have been nice to utilize, and the back-torque-limiting “slipper” clutch probably helped lap times, though I had no problems during aggressive downshifts on the conventionally clutched 636.
Of course, they’re fast-they’re Kawasakis. But 2003 marks the emergence of style in the middleweight Ninja lineup, and a strength that permeates the entire machine. Cutting-edge pieces and class-leading adjustability wrapped in a package that appears ready to stand the test of time, not just appeal to 17-year-olds. □
