Kawasaki Zx-6r
KAWASAKI ZX-6R
CW RIDING IMPRESSION
Japanese inquisition
DON CANET
WITH THE SWEET TASTE OF VICtory fresh in its mouth, Kawasaki is anxiously anticipating this year’s World Supersport Championship. Scotsman Iain MacPherson won the final two rounds of the 1999 season, placing him second overall for the year. And that was with the old ZX-6R.
Once again, the ultra-competitive demands of racing have prompted a new and improved Ninja ZX-6R. Performance gains have been achieved through a combination of reduced weight, increased power and various chassis upgrades. Led by Takashi Hiraga, Kawasaki’s engineers shaved 8 pounds from the 599cc, 16-valve, dohc inline-Four. Topping the list of changes are all-aluminum, linerless, electroplated cylinders that are said to be 25 percent lighter and more rigid than last year’s pressed-liner, open-deck block. Other benefits are longer wear and better heat dissipation, allowing tighter piston clearances for greater performance and reduced operating noise. The piston crowns and combustion chambers have been reshaped to improve squish area and raise compression to 12.8:1-up a full point from last year.
While crankshaft weight was reduced 12 percent, web diameter was increased to retain the proper inertia for optimum balance between response and tractability. New connecting-rod material increases strength to handle higher loads at peak revs. Thinner steel clutch plates reduce basket width to make the clutch assembly lighter than before.
Magnesium is now used for the valve, clutch and ignition covers. The net result is that the engine is now “snappier” and revs to 14,500 rpm-500 higher than before.
Revised ram-air inlet ducts—claimed to substantially increase airbox pressurization at speed-feed a bank of new Mikuni 36mm semi-downdraft carburetors equipped with a K-TRIC throttleposition sensor. An exhaust catalyzer located in the stainless-steel tailpipe allows for correct carburetor calibration while meeting ever-tightening worldwide emissions regulations. Revised cam timing, shorter intake manifolds and a remapped ignition curve are among the tuning changes that contribute to a claimed 2to 3-horsepower increase throughout the rev range.
Weight loss was less dramatic in the 6R’s chassis program, where just 3.3 pounds were shed. Instead, chassis designer Nobumasa Taniguchi focused on improved handling. The swingarm now uses pentagonal box-section tubing with twin internal braces (rather than a single brace as before), and no longer employs rubber soundand vibration-damping inserts. Rear-suspension linkage geometry was altered to provide a more linear rate, while grease nipples were added to the swingarm pivot and shock linkage to ease maintenance.
Up front, 5mm-wider triple-clamps hold a 46mm cartridge fork. The clip-on bars are now located beneath the top clamp, allowing for shorter fork tubes to save weight. While rake remains unchanged at 23.5 degrees, trail has been increased to 3.7 inches for improved stability. A taller 120/65ZR17 Dunlop D207 Sportmax radial replaces the old 60-series front tire for improved bump absorption, and a wider 180/55ZR17 rear tire increases grip.
I joined an international cast of motojournalists in Valencia, Spain, for a two-day test session aboard the latest ZX-6R. Named in honor of a Spanish motorcycle-racing hero, the recently constructed, 2.9-mile, 14-tum Circuit Ricardo Tormo was designed with motorcycle racing in mind. Suffice it to say, the state-of-the-art venue (which hosted its first Grand Prix in 1999) offered an ideal environment in which to explore the 6R’s limits.
As was the case with its predecessors, the 6R’s riding position is sporting while not so aggressive as to rule out extended street rides. Engine vibration is subtle (and particularly smooth at freeway speeds), wind protection is quite good when the rider is seated upright, and the clear screen is tall enough to duck behind in a full racing tuck.
Power delivery is nearly linear, with subtle steps at 5000 and 9000 rpm. Pin the throttle in first gear and the latter
step will loft the front wheel-clutch not required! In fact, snapping the throttle open while tugging on the bars made the Ninja stand up coming out of the second-gear comers.
Unlike on the street, a racetrack tends to eat up every bit of energy a bike can muster. Keeping the rev-counter above
10.000 rpm produced the best drives off comers, an easy enough task as the revlimiter doesn’t cut in until an indicated
15.000 rpm. The nicely spaced sixspeed gearbox shifts smoothly and the clutch has very good feel.
Things got interesting on the second day of our test when Taniguchi and crew dialed the suspension settings to suit the racetrack, with a taller rear rideheight, increased shock-spring preload and near-maximum shock rebound damping. Several Kawasaki and Dunlop engineers had stopwatches in their hands as I headed onto the track. Pressure to perform? You betcha!
Jacking up the rear had improved tum-in response without upsetting stability on the brakes. The front tire also felt a bit more planted when driving off comers with the throttle pinned. I was tmly impressed by the level of grip offered by the standard street tires. My confidence in the front end allowed me to trail-brake deep into comers, planting a knee while still applying brake pressure. This says much for the improved feel and sensitivity of the bike’s dual six-pot calipers, which now have smaller diameter leading pistons and revised pad material.
Cornering clearance was exceptional, as well. Although the folding footpegs touched down at a race pace, the sidestand and engine covers stayed out of harm’s way. The engineers were impressed that I grounded the muffler canister, but when they discovered I’d also scraped the leftside fairing lower, they asked me to autograph it! Apparently, this had never happened before.
As fate would have it, however, a fellow American journalist crashed that very bike later in the day. So it’s just my luck that one of the world’s first wadded millennium-model ZX-6Rs bears my John Hancock!
