Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/128198
ZX-6R POWERPLAI1T (Above) The ZX-6R features all new bodywork for 2003 including the menacing new headlights. The new Ram-air intake feeds the air straight through the frame and into the alrbox for maximum efficiency. (Below) The gauge assembly is a drastic departure from the old analog cluster on last years bike. The new LCD tach and speedometer are easy to read and as slick looking as they come. An odd thing happened in Kawasaki's planning for the 2003 model year: The company decided that it shouldn't be held back by the parameters and rules of racing when the product they are making is being made for the street. So why stick to the formula that dictates a middleweight sportbike must have a 600cc motor? Why not make it bigger for the street, and make another limited version to meet the rules for Supersport racing? So that's what the company did. Hence the ZX-6R is a 636cc-powered middleweight streetbike. Bigger is better, right? The motor in the ZX-6R isn't just a bored-out version of last year's engine, it has been completely redesigned for this application. Okay, they did have to bore it out from 66 to 68mms to get the displacement they wanted, but there is more to it than that. The crankcase itself was redesigned and is not only lighter, but was redesigned to allow the oil jets for the pistons to reside closer to the pistons. The crankshaft itself is all-new and has l.3mm less stroke than the unit it replaces; subsequently the connecting rods are now longer to keep the measured stroke at 43.8mm - the same as last year's. The biggest changes to the engine were made to the head and cylinders. The cylinders themselves are now 5mm shorter and have chrome composite plating directly on the aluminum surface instead of using liners. The shorter cylinders necessitated that other changes be made to the heads, such as 10mm shorter valves, which improves efficiency, especially at high-rpm operation. The valve springs no longer use inner and outer springs, but use new individual oval springs. While we're on the subject of the valvetrain, the camshafts are new as well and now feature bolt-on. adjustable sprockets. In addition, the pitch of the cam chain is now narrower to save weight. Okay, enough about those details. The big news is really the fuel-injection system now there isn't a single bike in the 600cc Supersport class that is without it. The system on the ZX-6R features 38mm Keihin throttle bodies, with what Kawasaki calls sub-throttle bodies to smooth out the power characteristics. The computer on the ZX-6R is new as well and features a 32-bit high-speed microprocessor to control not only the ignition, but the other functions involved in the fuel-injection system. Air is fed into a redesigned airbox via an all-new ram-air system that utilizes passageways in the headstock of the frame for the ducting that gives the air a more direct shot into it. This not only improves the airflow efficiency, but it saves weight by eliminating other ducting, The new air filter is an oiled-paper element that requires no servicing and only needs to be replaced every 11,000 miles. The exhaust system is all-new and is now made out of stainless steel instead of aluminum to help improve the performance of the new larger catalytic converter. This is aided by Kawasaki's KLEEN (Kawasaki Low Exhaust Emission) system, which includes an air-injection system and the secondary air reed valve. The ZX-6R has a curved radiator that features a new ring-type fan for improved cooling efficiency, and was also made more compact to help improve the aerodynamic efficiency of the bike's frontal area. roughly 20 to 25 minutes in length, colors (a first for Kawasaki). The we were constantly riding and Not only has the engine been improved for '03, but the transmission was improved as well. The shift cam and the shift drum have both been modified to improve shifting, while the ratios have been tightened up between gears three through six for improved performance. Spring Mountain track is also ideal swapping bikes, though the majority of our time was spent with the 636, which will be available in four for testing 600s, with a favorable collection of both fast and slow corners as well as a long straight- away that allows the bike to find its legs. The first thing I noticed after hopping aboard the 6R for the first time was its brakes. Though I can't say I hadn't been forewarned. After cruising out of the pits and around the medium-speed right/left combination that makes up the first two corners at Pahrump, I headed toward turn three just feeling my way on a track I hadn't ridden on in a long time. I arrived at turn three at a leisurely pace, grabbed the front brake and ... wham! I was stopped. I actually had to get back on the gas just to make it to the apex without embarrassing myself completely. Apparently, I didn't take seriously an earlier conversation I'd had with Hayden. "The brakes are unreal," he'd told me over morning cereal. "The best I've ever ridden with - on anything." Put it this way: Most of us have done all of our braking and have bal- The ZX-6R is all-new for 2003, having been redesigned from the ground up. cue I .. n e _ S • JANUARY 29,2003 15