Zx-9r Zx-6r
NEW FOR KAWASAKI 98
ZX-9R ZX-6R Faster, racier, lighter, cooler
K AWASAKI HAS HAD A CONTINUING problem with its ZX-9: the Honda CBR900RR. A natural competitor for Kawasaki's sportiest big-bore, the featherweight Honda was able to better the ZX-9's power-to-weight ratio even while trading peak power for a wider powerband. Sure, some riders preferred the heavier steering, more stable Kawasaki, but the Honda went on to become one of the best selling motorcycles of the mid Nineties, especially in the sport intensive European market.
This Year, Kawasaki aims to have the perfect foil to the Honda threat: a new 9 with a new engine, a bike claimed to be more powerful than last year's 125horse-at-the-rear-wheel version, and said to weigh about 70 pounds less. The new bike should be the quickest Kawasaki ever sold, and promises to smoke last year's Honda-if not its rumored, updated-for`98 replacement.
The new engine is at the heart of both the power increase and the weight reduction. With 75mm bores, the 9's powerplant makes room for 1mm-big ger valves, and allows the stroke to shorten from 53.7mm to 50.9mm, increasing rev potential. A transmission sharing shaft spacing with the ZX-6's shortens the engine's overall length, while wider gears handle the increased power. A clutch from the 6 transmits that power by means of an additional plate, while the loss of the old clutch's back-torque eliminator and the substitution of cable for hydraulic actuation further cut weight. As on the 6, the alternator now is driven off the left end of the crankshaft-saving the cost and mass of a chain drive and a jackshaft. Expensive rare-earth mag nets keep the alternator small and narrow to avoid impairing cornering clearance, and pare off another pound. Magnes-~ ium serves for almost all the engine covers, while
a titanium canister houses the muffler.
All in all, the new engine scales some 20 pounds less than the old in a more compact package, and is claimed to make a few more horses than its already stout predecessor.
Carrying the new engine is a shorter and lighter chassis. Chopping an inch from the old 9's wheelbase has reduced the span between axles to a 600-class number: 55.8 inches. Weight has been shed through a myriad of small cuts. As examples, the front discs are now an inch smaller; front downtubes have been eliminated entirely; the swingarm is now fabricated wholly from highstrength extrusions; the instruments are flyweight electrically operated units; the wheels have thinner sections; and the headlight has a polycarbonate rather than a glass lens. Kawasaki claims a weight (minus fuel) of 431 pounds for the prototype machine pictured here-if that holds for the production bikes, the new 9 will weigh within a few pounds of the current Honda 900, less than some 600s, and about 150 pounds less than the comparably powerful ZX-1 1. This should be a rocketship.
Emphasis on the new 9 remains sporty street riding, however, with the riding position similar to last year's bike: clip-ons above the top triple clamp, and footpegs farther from the seat than those of 750 race-replicas.
That's different from the `98 ZX-6R, which definitely follows the "Race on Sunday, Sell on Monday" philosophy. The old 6's engine returns in refined form with the addition of the same mapped, throttle-sensitive ignition sys tem used on the new 9, and perhaps a few other yet unspecified internal changes to boost power-production is still four months away as this is writ ten, and final engine specifications have yet to be locked down.
What is certain are a number of changes to make the 6R more trackworthy. Wheelbase has been chopped a half-inch to 55.0 inches, while rake has been reduced to 23.5 degrees, all for more responsive handling. A bolt-on aluminum subframe gives much better access to the piggyback rear shock, which now comes with a ride-height adjuster. The rear rim size has grown to 5.5 inches to mount the latest 170to 180-size rubber. The tubes of the conventional front fork have expanded from 41mm to 46mm for greater stiffness under braking and cornering loads. A new fairing is more aerodynamic than the old. And finally, a number of small changes-magnesium engine covers, plastic headlight lens, aluminum shift lever and muffler can, etc.-have contributed to an overall weight reduction of 12 pounds.
So, with racy refinements to an already strong 6, and perhaps the best power-to-weight ratio in motorcycling for the 9, Kawasaki enters the `98 model year with a potentially crushing sportbike lineup. Steve Anderson
