1995 Kawasaki Zx-6r
CYCLE WORLD TEST
1995 KAWASAKI ZX-6R
JUST THE LIGHTEST, QUICKEST, FASTEST, MOST POWERFUL 600, IS ALL
EVER BEEN THE TOAST OF THE BALL, only to be upstaged by a fashion ably late arrival? Well, that's how the boys at Honda gotta be feeling after reading the performance numbers just posted by Kawasaki's latest entry into the middleweight sportbike fray.
The rubber hadn’t even cooled on the 1995 CBR600F3, which set an impressive new 600class mark of 11.05 seconds in the quarter-mile, and Kawasaki pulls the tarps off the all-new ZX6R. which proceeds to click off a 10.89-second run to become the first-ever stock 600 to break into the 10s, previously the domain of Openelassers and fast 750s.
Rumor has it that Kawasaki, anticipating a lightweight supersport CBR600RR from Honda in '95, unveiled the ZX-6R as a countermeasure. Now, they find themselves in
the peculiar position of having worn a tux to a tailgate party. The thing is. a fine suit isn't inexpensive, and at $7899 neither is the ZX-6R.
Right up until this year, Kawasaki's old-style ZX-6 offered class-leading power. Although the ZX-6 will remain in Kawasaki's lineup in '95, the new 6R pushes the performance envelope well beyond that of the standard 6. Not only has power output been substantially boosted, the new bike adds top-drawer suspension, sharper handling and racetrack-ready cornering clearance. Kawasaki's ambitious design goal was to build the lightest, most powerful, most compact engine in the class. Working from a clean sheet of paper, company engineers have come up with an all-new, 599cc, liquid-cooled inline-Four that improves upon the previous 600 engine in many areas.
To start with, they've moved the camshaft drive chain from the center to the right end of the crank (a /a ZX-7), allowing the new crank to turn in five plain bearings rather than six for less frictional loss. Cam-drive relocation has closed the spacing of number two and three main journals, giving the crank a substantial increase in torsional rigidity that has allowed a 2mm reduction in main-journal diameter for further friction reduction. Overall, the 6R’s crank is 1.2inches narrower and lighter than that of the ZX-6.
A wider bore diameter of 66mm (increased 2mm) has allowed for larger-diameter valves, while shortening the stroke has lowered piston speed, enabling higher revs. Piston weight has only increased 9 grams, due to the use of a slipper-type skirt. With the cast-aluminum piston's convex top and the head’s pent-roof combustion chambers, compression ratio has been lowered from 12.0:1 to 1 1.8:1. New cylinder liners have short skirts to allow free movement of air for reduced pumping loss within the crankcase.
Positioning the cam drive to the side has also made for more evenly spaced ports, yielding a straighter, shorter combustion path than that of the ZX-6. The new engine’s cylinder bank is canted forward 28 degrees (13 degrees more than the ZX-6), with the overall downdraft angle of its four 36mm Keihin carburetors at 68 degrees, compared to the ZX-6’s 49 degrees. Included valve angle is 25 degrees (5 degrees less than before) for a more compact head and straighter, more efficient ports. Intake-valve diameter is 27mm, measuring 1mm over the ZX-6, with a .6mm increase on the exhaust-valve size, now at 22.6mm. Intake valve timing and lift are slightly hotter, with 316 degrees of duration and 9.0mm of lift, up from 308 degrees and 8.8mm. Exhaust-cam specs are unchanged, although cam timing has been retarded 3 degrees. The improved breathing and reduced piston speed of the new engine has allowed a 700-rpm increase in peak revs, calling for slightly stiffer valve springs to avoid valve float at redline.
As good as all this looks on paper, the 6R's engine performance is even more impressive in action. On the dyno, the ZX-6R cranked out 95.2 rear-wheel horsepower at 12,000 rpm. That’s 8 more ponies than last year’s ZX-6 and 6 more than the 1995 CBR600F3. Only two years ago, frontline 750cc repli-racers did well to produce that kind of power. At the dragstrip, the 6R’s 10.89-second, 128mph pass makes it the quickest 600 ever.
In fact, it’s only two-tenths of a second and 3 mph slower than Kawasaki’s own ZX-9R. On its stunning top-speed run, the ZX-6R finally ran out of steam at 154 mph, almost 10 mph up on the Honda F3. This, friends, is one very quick, very fast, very powerful 600.
In the past, we’ve cited Kawasaki 600s for sloppy shifting action and excessive drive lash, mainly in the lower gears. The ZX-6R has an all-new, and extremely slick-shifting, six-speed gearbox that is much more compact fore and aft than that of the ZX-6. The input shaft is located six-tenths of an inch closer to the crankshaft and the distance between input and output shafts is about threetenths of an inch closer than before. In a first for Kawasaki, involute (spirally cut) splines-instead of straight splines—have been used on the shift shafts for reduced sliding resistance and radial play on the gears. The gears themselves are now thicker to reduce incline angle when external force is applied, and second through sixth gears now have five undercut dogs rather than six.
The cable-actuated clutch contains two additional steel and friction plates, although they are all of smaller diameter than the ZX-6's. A #525 X-ring chain has been fitted and is said to run cooler and last longer than a conventional O-ring chain.
Cooling capacity of the flat-type radiator has been improved to match the engine's increased power output. The thermostat is located in the head to eliminate various brackets and hoses. An oil cooler supplements cooling and a spinon oil filter has simplified oil changes.
A special baffle in the 4-into-2-into-1 exhaust system’s tailpipe is claimed to maximize pulse effect for increased torque. The silencer body is made of aluminum rather than steel to reduce weight and centralize mass, a first for a U.S.market Kawasaki.
The 6R gets a new perimeter-style frame made of pressed, then welded aluminum sheet, and is partly responsible for the 6R weighing-in 44 pounds under the old-style 6—Kawasaki says the new frame saves 6.6 pounds. The boxsection extruded-aluminum swingarm was taken directly from the ZX-6 without modification. Both frame and swingarm beams have internal rubber inserts to absorb harmonic resonance caused by vibration. Likewise, damper rubber is used inside the engine's clutch and generator covers for same reason.
To quicken-up the 6R's handling, rake has been reduced a half degree, trail shortened .35 inch and a half-inch was shaved from the wheelbase, compared to the ZX-6. A fully adjustable 41mm KYB conventional cartridge fork carries the load up front. A KYB shock fitted at the rear offers adjustable compression and rebound damping, spring preload and ride height. Bridgstone Battlax tires are fitted to three-
spoke, east-aluminum, 17-inch wheels, 3.5 inches wide up front, 5.0 inches wide at the rear. Standard suspension settings offered an excellent all-around ride for the street, and felt good at the track, though we dropped lap times a full second at the Streets of Willow after dialing-in more spring preload, and additional compression and rebound damping at both ends for a firmer, more controlled ride.
Stopping power is provided by a pair of four-piston calipers acting on radially drilled, 1 1.8-inch, semi-floating, stainless-steel rotors up front. At the rear a 9.0-inch rotor is gripped by a floating, single-piston caliper. The front brake provided excellent two-finger stopping power with progressive feel. After several hard laps on the track, the lever got a bit soft, but never came back to the grip. Both the clutchand front-brake levers allow position adjustment to suit individual riders’ hand spans.
Twisting the handlebar-mounted choke lever full-on made for easy cold starts. Backing off the choke a bit sustained a moderate idle speed during engine warm-up, unlike some ZX models that seem intent on high revs or nothing while on the choke. Despite the 6R’s top-weighted powerband, pulling away from stops requires no major gymnastics of and dutch, but as the revs pass between and 4000 rpm. there is a distinct stumble, ith the engine fully warm, the power dip persists, regardless of throttle position or load. Once clear of 4000 rpm, the engine pulls cleanly to its 14,000-rpm redline, though in the lower gears, you feel slight bumps in the power delivery around 7000 rpm and again at 9000 rpm.
Midrange power is quite good. Snapping the throttle open around 6000 rpm in low gear will bring the front end right up. Engine revs range between 4500 and 6000 rpm while traveling at freeway speeds in top gear. At this pace, engine vibration is minimal, with plenty of roll-on torque on tap for passing without a downshift. On backroads, keeping the revs between 4000 and 8000 rpm is enough to really cook along-and to think there’s another 6000 rpm worth of steam in reserve. That’s hot.
Like all members of the ZX family, the 6R likes to stretch its legs. Not only is the bike capable of top speeds greater than some 750s, it’s rock-steady while doing so. More importantly, this stability is evident at all speeds and lean angles. Like the ZX-6 before it, the 6R’s steering is light and neutral, however where the ZX-6 digs its pipes, sideand centerstand into the asphalt when cornered aggressively, the 6R hasn’t yet approached its bounds. Ultimately, tire grip proved to be the 6R's limiting factor on the road course; we touched down nothing more than the footpegs.
For all its worth on the track or in the twisties, the 6R still offers civil enough ergonomics for daily use. Like its larger sibling ZX-9R, the 6R’s riding position strikes a balance between full-race and sport-tour. The seat is a bit firm yet very spacious and well shaped. At the rear, bungee-hook points, passenger grab rails and an underseat storage compartment designed to hold a U-type lock all add to the 6R’s street relevance.
Has Kawasaki blown the competition into the weeds with this new ZX-6R? Well, a 95-horsepower, 10-second, 154mph 600 carries some powerful persuasion, whether in the showroom, along Main Street or up on the Daytona banking. On the tight, twisty Streets of Willow race course, though, the 6R, unable to showcase its horsepower and top-speed superiority and hampered by tires that seemed to go off fairly quickly, tuned in lap times exactly equal to those set a month earlier by the Honda F3. And now comes the news that Yamaha, holder of the 1994 AMA 600 Supersport title with its YZF, is about to introduce a hotted-up version of that bike, just in time for Daytona.
So, let's not pop the champagne just yet; first, we must gather all the players together, same day, same track on the same type of tires. We can say, though, that both Honda and Yamaha will definitely have their work cut out for them.
KAWASAKI ZX-6R
$7899
EDITORS' NOTE
I CAN’T HELP YOU IF YOU WANT TO know what’s the best 600. I’m not sure yet. But I’ll let you in on a secret: It’s going to be close.
Forget lap times and championship battles for supersport supremacy for a second, how good is the new ZX-6R on its own? During testing we had our Kawasaki ZX-9 out for the ride. Back-
to-back switchoffs gave me a feel for how nimble the 600 truly is. And the 6's torquey power wasn’t a letdown after riding the 9. I felt more like a racer riding the smaller Kawasaki. It gave me a bigger adrenalin rush on the Streets of Willow racetrack-the 900’s extra weight and girth was not worth the boost in power.
The 6R’s noticeable improvements in shifting, a lighter feel and more power reminded me more of Miguel DuHamel’s 1993 supersport-winning racebike than 1994’s ZX-6 production bike. 1 like that-a lot.
-Jimmy Lewis. Off-Road Editor
To ME, WORKING THE TWISTIES IS WHAT sportbikes are all about. All the ZX-6R needs is gas in its tank and the proper air pressure in its tires, and it’s ready to take on the best corner-carvers this or any other class has to offer. No centerstand to remove, no wimpy suspension to hold me back, no excuses whatsoever. And if there happens to be a long straight between two curves, I can relax
in knowing the 154-mph 6R has that covered as well.
It’s been a long time since we’ve been able to say all this about a Kawasaki middleweight. What’s more, the ZX-6R is not some uncompromising package only fit to be wearing safety wire and numberplates. It’ll also pull sport-touring duty without complaint.
Man, what a year thus far. First the CBR600F3 and now the ZX-6R. Both excellent bikes, on and off the track, upright in sight-seeing mode or leaned over and throwing sparks. -Don Canet, Road Test Editor
I WOULD NEVER BUY THIS MOTORCYCLE. Don’t get me wrong; I’m thoroughly impressed with what Kawasaki has done here. Remember, this is the company that brought us the ground-breaking Z-l, the irreverent HI Triple and the eye-widening, 176-mph ZX-11. For the ZX-6R to be anything less than a twowheeled missile would be a failure.
My concerns are with the bike’s ergonomics, at least for those of us over 6 feet tall. While last year’s ZX-6 was the class comfort king, easily outfitted with soft saddlebags for a week’s worth of sport-touring, the R model is more narrowly focused. Sure, it’s sporttourable, but with its low, clip-on handlebars, rearset footpegs and thin seat, I find the ZX-6R better suited to slipstreaming the competition on the high banks of Daytona.
For me, though, the most compelling reason not to buy a ZX-6R is its price. Eight grand will easily cover the cost of two of my favorites: a used-and much more versatile-CBR 600F2 and a new KDX200 dirtbike.
-Matthew Miles, Managing Editor
