Kawasaki Zx-9r

KAWASAKI ZX-9R

CAN LIGHTNING STRIKE THREE TIMES?

DON CANET

THE 900cc CLASS HAS ALWAYS been good to Kawasaki. Twenty years ago, the company introduced the block-buster 903cc Z-1, followed 10 years later by another milestone motorcycle, the Ninja 900R, one of Japan's first serious sportbikes. So, it’s no coincidence that Kawasaki has returned to the 900 class in ’94.

The new ZX-9R draws heavily on technology already present in other models of the ZX family. This gives it fine breeding. But, we wondered, has Kawasaki’s use of trickle-down technology given the 9R the impact that made its predecessors the stuff of legends?

For insight, Cycle World jetted to Kuala Lumpur, Malaysia, situated in the heart of Southeast Asia just north of the Equator, site of the ZX-9R’s world press introduction. The plan called for two days of riding at the Shah Alam Circuit, a world-class road course, followed by a ride on public roads to Port Dixon, a rustic seaport town on the west coast of Peninsular Malaysia.

The ZX-9R’s 899cc, liquid-cooled, 16-valve, dohc, inline-Four closely follows the ZX-7’s race-proven design. The 9R gets a beefed-up bottom end to deal with its increased bore and stroke of 73 x 53.7mm. The crankcases have been strengthened in key areas and use larger main-bearing journals along with crankpins of increased diameter. The engine retains the ZX-7’s rightside, crank-end camdrive, which provides increased torsional rigidity by allowing a narrower overall width than possible with a center-camdrive design. The engine uses surface-hardened chrome-moly connecting rods with sturdy big-end bolts and nylock nuts for reliability.

Farther up, the 9R has concavetopped, cast-aluminum pistons that deliver a compression ratio of 11.5:1. Barrel-faced compression rings are used for improved sealing and durability. An inner bevel on the rings wards off flutter by allowing each ring to twist slightly and wedge itself inside its grove.

The 9R’s cylinder head employs pent-roof combustion chambers with 20-degree included-valve angles and centrally located, 10mm, dual-electrode sparkplugs. Valve sizes are 29mm intake and 25mm exhaust, each valve controlled via a single, dual-rate spring and its own lightweight, spring-loaded rocker arm. Adjusting valve lash simply requires sliding the rockers to the side and changing shims. A locater

spring loops over the top of the rocker and holds it lightly against the shim to reduce tappet noise. As a result, the 9R is a quieter-running motor than previous Ninjas. Camshafts are hollow, each riding in four plain bearings and a single roller bearing located just inboard the drive sprocket, which is pressed onto the right end of the camshaft.

All this results in an abundance of power over a broad rpm range, with a very linear increase in power as the revs climb to the 12,000-rpm redline.

Worked hard on the racetrack, the motor felt strong and smooth. The power was even more impressive out on public roads, though a fair level of engine vibration was more easily noticed here. Vibration doesn’t pass through the tank or mirrors, and the bike never produced any audible buzz or rattles, but during sustained freeway cruising, engine vibration passing through the bars and pegs may be a bit bothersome for those who go sporttouring on the ZX-9R.

Like the ZX-6 and ZX-11, twin ramair inlets originating beneath the headlight funnel cool air through a pair of ducts back to a 12-liter airbox under the fuel tank. The airbox houses a good-sized oiled-foam air filter and incorporates velocity stacks that fasten to the mouths of four 40mm Keihin CV downdraft carbs. Carburetion was very good, delivering clean, crisp response under various loads. Another plus: For the first time in a while, this

is a new Kawasaki without objectionable amounts of drivetrain lash.

Unfortunately, the ZX-9R’s six-speed gearbox isn’t as praiseworthy. The undercut tranny shifts smoothly up through the gears under hard acceleration and does almost as slick a job in short-shift cruise mode. However, a vast majority of editors riding the 20 or so ZX-9Rs present at Shah Alam complained of catching occasional false neutrals when downshifting. My own experience aboard a trio of 9Rs showed that a properly timed blip of the throttle made for cleaner downshifts, yet the phantom neutral still lurked between third and fourth gears when I wasn’t extra deliberate changing down. A spokesman for Kawasaki said engineers will look into rectifying the problem, but it seems late in the development cycle for any major changes.

Another problem on the racetrack was the rear tire’s tendency to overheat on the admittedly hot asphalt of the Shah Alam Circuit. Although the Bridgestone Battlax BT50 radial tires that come fitted to the ZX-9R perform very well on public roads, the 180/55ZR17 rear was only good for four or five fast laps around the 2.2mile, 14-turn track before it started skating through corners. In all fairness, the initial level of grip I experienced with a fresh BT-50R rear was quite impressive, and even after the compound had gone off, the tire remained very predictable when sliding. The bike’s 120/70ZR17 BT-50F front-in Bridgestone’s SS racing compound-worked exceptionally well throughout the test.

The controllability of rear-end slides

must in part be credited to the ZX-9R’s superb chassis. Patterned after the ZX7’s frame, the 9R’s perimeter-type structure is constructed of welded pressed-aluminum sheets and castings. Aluminum downtubes mimic those of the first-generation ZX-7 frame, providing additional rigidity and points for two rubberized engine mounts that supplement two rear, solid-mount points. A bolt-on rear subframe is made of square-section aluminum tube, while the swingarm is constructed in the same manner as the main frame.

Chassis geometry is very close to that of the ZX-7, with 24 degrees of rake and 3.7 inches of trail, compared to the ZX-7’s 24.5-degrees/3.7 inches. The 9R’s wheelbase stretches 57.6 inches, slightly longer than the ZX-7’s 56.3 inches. Steering effort is a bit heavier, yet neutral with a good feel for what the front tire is doing. Although a minor amount of steering oscillation is detectable around 45 mph, the bike never exhibited the slightest tendency for headshaking over rough pavement. The 9R has inherited the excellent high-speed stability that has been one of the ZX-7’s most admirable traits.

A KYB cartridge fork is adjustable for compression and rebound damping, along with spring preload, and seems well suited for fast road work without being too harsh for sport-touring use. As with the ZX-7, the rear ride height may be adjusted via a threaded top-shock mount. As it sits stock, cornering clearance is excellent, with only the footpeg feelers touching down during the hardest laps any of the Americans present-including World Superbike Champion Scott Russell-could muster around the ultra-smooth Shah Alam track.

The KYB rear damper has a remote reservoir with adjustable compression damping and a four-position rebound knob on the shock body, along with a threaded spring-preload collar. Unfortunately, journalists were not permitted to make suspension changes during the press intro, so our suspension evaluation of the ZX-9R is less than complete.

So, what to say about Kawasaski’s 900-class reentry? It’s interesting, yes, good-looking and fast, but the gearbox glitches are bothersome. Kawasaki’s designers seem to have aimed lower than the lightweight Honda CBR900RR repli-racer and higher than the new Suzuki RF900R all-around sportbike. Time and a stateside test of the ZX-9R will show how true their aim really is. □