Kawasaki GPz 900R Ninja

In 1984, the new GPz 900 Ninja was the cutting-edge of performance, with an all-new liquid-cooled four-cylinder driving its cams from the left side instead of the middle—the better to lean over farther in corners and produce top-end power that put the big air-cooled multis of the day to shame. Thirty years later, the old beast reminds us why Kawasakis used to be thought of as unbreakable but a bit crude: On serial #0001, black primer shows through the red paint on part of the fairing and many of the stickers are just that, stuck on. None of it mattered; in 1984, the median Baby Boomer was 29 years old and making decent bank working the second shift at the Budweiser plant in Van Nuys, California, cruising the boulevard after work in Oakley Blades with a mullet for a helmet.

We called the new Yamaha FJ1100 introduced the same year “the fastest, most competent all-around liter-class sportbike of them all.” But when it came time for “Ten Best” in 1984, the Kawasaki was it: “This isn’t your usual Japanese sportbike... this is a hard-core performance motorcycle aimed directly at the hard-core performance rider.”

Here’s the thing about the original Ninja, though: It was hard-core before the core became so hard. Never mind the period hyperbole, your Open-class streetbike of 1984 was also a pretty good daily ride/sport-tourer. The old hausfrau Ninja weighed 546 pounds with half a tank of fuel (2.9 gallons); the new ZX-10R that Tom Sykes’ World Superbike champion bike is based upon is nearly 120 pounds lighter. That’s an entire Dani Pedrosa.

Review

Kawasaki says it is a new generation of street bike, and it is probably right. But the ZX900 also harkens back to a lost era, an era that ended, ironically, with the advent of the Kawasaki 903 Z-1. The Z-1 ushered in a decade of street bikes that were broadly targeted, fat in the powerband and, despite unprecedented power and performance, somewhat short on personality. The ZX900, on the other hand, is aimed straight at the sporting rider who takes power and cornering very seriously. Even its name, Ninja, takes you back to the era of Kawasaki's

A1 Samurai and A7 Avenger, bikes that, like the ZX900, were aggressive, high-strung animals. In those days, just the word Kawasaki could start a heated debate about whether a 350 Avenger could really beat a 650—and many 650 riders would turn a corner or ride out of a parking lot before the issue could be resolved by combat. In 1984, the debates will swirl around the question of whether the Kawasaki ZX900 Ninja can give away 100 to 250cc and still be competitive with monsters like Honda's VF1000 Interceptor and V65 Sabre, Suzuki's GS1150 and Yamaha's FJ1100. Some of the answers to such questions emerged during our testing, and the Ninja stands as a very strong contender in the Superbike War of 1984.

With V-4s popping up everywhere in Honda's '84 lineup and Suzuki and Yamaha likely to add or introduce V-4s by '85, it must have been tempting for Kawasaki to join the parade. Instead, Kawasaki chose to advance the in-line four, introducing an engine which is at once conventional and exotic, an engine that is completely competitive with the latest V-4s. It is, as Kawasaki says, an in-line four for the '80s.

Kawasaki considered sixes and V-4s before settling on "the proven configuration." Kawasaki cites several advantages for the in-line four: evenly spaced power strokes, near-perfect primary balance, simplified service, relatively few moving parts, low mechanical losses and efficient combustion flow. To these qualities, Kawasaki added several innovations to make a power plant that is completely competitive with the V-4s that have received so much attention in the last couple of seasons. Most of the innovations—like generators and other accessories mounted behind the cylinder bank, four-valve combustion chambers and liquid-cooling—are new only for Kawasaki. However, they have been assembled in a combination and configuration that are thus far unique and offer many advantages.

Two factors more than any others distinguish the ZX900 design from other in-line fours. The first is liquid-cooling, a common inclusion on other engine configurations but thus far conspicuously absent on in-line fours. By using a water-cooled rather than an air-cooled design, Kawasaki could slim things down. The wet-liner system is quite compact, as is the aluminum cross-flow radiator. The radiator holds just three-quarters of a quart and weighs under three pounds. In addition to the radiator, the cooling system includes a thermostat which actuates at 187 degrees F, an electric fan which turns on at 207 degrees, an overflow tank under the right side panel, and the water pump, which is driven by a gear from the clutch. Coolant is pumped into the front of the cylinder block, up through it to the head and then to the radiator. Kawasaki cites improved cooling as the leading factor enabling it to use a stiff 11:1 compression ratio and still accept unleaded fuel. The more consistent engine temperatures also enabled the designers to specify tighter piston clearances in the pressed-in cylinder liners and reduce piston-ring tension.

Liquid-cooling coupled well with the decision to mount the drive chain for the camshafts at the left end of the crankshaft. The cam-chain-drive location provided many potential benefits in addition to simplifying the process of water-cooling. It enabled Kawasaki to further slim the engine by reducing the number of crankshaft bearings. It also provided easy access to the cam-chain adjuster, and, according to Kawasaki, the resulting even spacing of the bore centers made symmetrical arrangements of ports, sub-ports and combustion chambers possible. The resulting short, straight combustion paths "significantly improve breathing efficiency," according to the designers. The cam chain itself is a "silent" link-plate type with a hefty 7.94mm pitch. It's tensioned by Kawasaki's new constant-load tensioner and drives a pair of hollow camshafts, each riding on five plain-bearing surfaces in the head and each with four lobes. A reusable rubber gasket seals the cam cover. The head gasket is laminated steel, and the base gasket is steel sheet.

The ZX900 is Kawasaki's first street bike with four valves per cylinder, a feature which adds a bit of complexity and has become commonplace among the high-performance street bikes of the other Japanese firms. Until now, Kawasaki has generally managed to set—or at least match—the standard of performance without this extra bit of complication and expense. Four-valve combustion chambers had been tried extensively at Kawasaki, but they weren't deemed worthwhile until now—when there is an entire engine designed to utilize them. As discussed in the accompanying development feature, Kawasaki felt that effective use of four-valve combustion chambers relied on more than just a new head design.

Each pair of valves is operated by a forked, two-finger cam follower. Valve lash is regulated with threaded adjusters. The valve sizes are 29mm on the intake side and 24.7 on the exhaust side. Duration and lift are the same on both sides, 290 degrees and 9.3mm, respectively. The included valve angle (the angle of the valves relative to each other) has been decreased sharply compared to recent GPz models. At 34.9 degrees, it is over 25 degrees narrower than the 750 or 1100. The steep angles enabled Kawasaki to make the combustion chambers compact and to shorten the ports.

A unique set of constant-velocity carburetors is used. The 34mm Keihin CVK carbs are similar to those used on last year's Team Kawasaki Superbike racer. They have semiflat throttle slides to reduce length and weight and also improve throttle response, fuel mixing and intake velocity.

Another feature used previously but never on an in-line four built for a motorcycle is a counterbalancer. Gear driven directly from the crankshaft's primary gear (located between the No. 3 and 4 cylinders), the compact balancer is positioned just in front of the crank. Both its gear and the primary gear are polished to reduce mechanical losses and lash. The one-piece crank rides on five plain bearings, and lubrication is provided through a two-loop system. One loop simply circulates oil through the four-pass cooler mounted below the radiator in front of the sump. The other circulates oil through the engine, gearbox and oil filter, with an external line delivering oil to the head. This two-loop system keeps the cooler from impeding oil flow to moving parts. The pump, which is driven by the same shaft that drives the water pump, delivers a maximum of 71 psi.

The Ninja is the first Kawasaki with its alternator removed from the crankshaft's end to help narrow the engine. The air-cooled alternator is set back behind the cylinders with the starter and driven by a link-plate chain from the right end of the crank.

The machine is also the first big Kawasaki with a six-speed gearbox and a hydraulic clutch. To save space and help shorten the engine, the two shafts are staggered vertically in the gearbox. Third, fourth and fifth gears have undercut dogs. The No. 530 silicone-lubricated O-ring chain has its inner plates drilled to lighten it, reducing power losses and chain and sprocket wear.

The result of all this tightening, downsizing and reduction is an engine which is compact and light for its claimed 113 horsepower. It is just 18 inches wide and tapers at an angle similar to the fairing bellypan's V-shape, something you'll notice if you get down and look at the underside. This enabled Kawasaki to provide plenty of cornering clearance and still mount the engine low in the frame. The engine is also short front to rear and top to bottom. And Kawasaki says that even with the radiator and oil cooler it weighs 11 pounds less than the Z-1 engine. Overall, however, the bike is not remarkably light, despite early hopes for very low weight figures. At 565 pounds wet, the complete motorcycle is only 15 pounds lighter than the Suzuki GS1150 we tested two months ago.

However, considering that it is giving away 227cc, the GPz makes a good account of itself in power comparisons. The powerband is wide enough to give you a choice of three gears in most situations. Although there is more power at the top of the rev band, it is not necessary to keep the engine spinning up near the 10,500-rpm redline to get plenty of action when you twist the throttle. We usually just left it in top gear to pass on the highway, and the ZX900 steamed quickly past double-nickel traffic. Our roll-on tests, conducted in top gear from a 50-mph rolling start showed that the Ninja accelerated to an average of 80.7 mph after 200 yards. That is significantly slower than the Suzuki GS1150, which at 90.5 mph is the all-time uncontested champ. It's also a bit slower than the 1100 sport bikes, which range from 81.5 for the Honda CB1100F to 87.5 for the Suzuki GS1100S Katana. However, the Ninja has more top-gear punch than bikes like the Yamaha Venture, Harley-Davidson XR1000 or Suzuki GS1100G, and about the same as the Honda 750 Interceptor, the best of the 750s.

In terms of all-out sprinting power, the 900 Ninja is about equal to the Kawasaki 750 Turbo and just slightly quicker than any bike introduced before this year. Our official time, posted by Road Test Editor Jeff Karr at Baylands Raceway in Fremont, California, is 10.96 seconds at 122.3 mph. That is about two-tenths of a second slower than his quickest time on the Suzuki GS1150, which ran 10.73 seconds, 126.8 mph for him at Carlsbad Raceway. (At Fremont, Karr's best with the Suzuki was 10.81, but his best on the Kawasaki at Carlsbad was 11.2. Note that when our correction factor for the Kawasaki's time at Fremont is figured in, it comes up slower than the best time actually recorded because the barometric conditions were better than the sea-level standard conditions that we use as our standard for comparison. With this factor figured in, Karr's best time comes up 11.01 seconds at 121.8 mph. As they say in the gas-mileage ads, "Use this figure for comparison. Your times may vary.") Professional launch artist Jay Gleason had a ,15-second difference on the two when he ran them at Fremont, posting a 10.47-second run on the Suzuki and a 10.62-second run on the Kawasaki. Both bikes are rockets, but the Suzuki's extra 250cc makes itself felt with a power advantage under all conditions.

Whether you grab a fistful of throttle at 2000 or 8000 rpm, the Ninja responds crisply and without hesitation or pinging, no matter what the altitude. Throttle response is more linear than on some Kei-hin CV carbs we have sampled, and there are no abrupt lurches when you change throttle setting in a normal manner. The ZX900 warms up fairly promptly, and there are detents in the handlebar-mounted choke mechanism to help you find the right setting during warm-up.

Shifting was excellent. No one missed a shift during the test, and everyone rated gearbox action as smooth and positive. Kawasaki's automatic neutral finder, which won't let you upshift past neutral from first when the bike is stopped, makes that chore foolproof. Kawasaki's new hydraulic clutch offers a light pull and predictable, consistent engagement over a somewhat narrow span, permitting confident two-finger operation. The clutch proved its strength by standing up to over 40 full-goose launches at the dragstrip. Drivetrain lash was negligible.

Our fuel mileage on the Ninja ranged from 52 to 30 mpg, with our best tanks turned in during freeway cruising at about 70 mph. Our 40.9-mpg average would provide 237 miles of range if the 5.8-gal-lon tank were full. Incidentally, the locking fuel cap is a pleasure to use. It is hinged, so you don't have to find a place to put it while you are filling, and the opening is conveniently large. You don't need the key to close the cap again, either. The black fuel cap assembly is styled like a racing cap with alien bolts securing it to the tank, and it fits flush with the tank top.

Most sport bikes become uncomfortable in a hurry when you settle in for a long drone down a straight road. With its canted-forward riding posture and somewhat narrow seat, we expected to be miserable after a few interstate miles aboard the Ninja, but we were pleasantly surprised—and more than a little. The bike was quite comfortable for everyone who spent any time on it either touring or just during hour-long jaunts in light freeway traffic. At highway speeds the combination of slightly raised handlebars (the U.S. Ninja's bars are 1.2 inches taller than the European version's) and the wind pressure on your chest keeps the weight off your arms and hands, and the throttle return springs are light enough to prevent your wrist from pumping up right away. Even when riding in traffic for extended periods, we didn't have any complaints about the riding position, although one rider felt the seat's forward slope tended to slide him forward more than he preferred. The saddle is narrow but reasonably padded, so it took several hours of nonstop riding before it began to get uncomfortable.

The ZX900 Ninja is quite smooth for an in-line four, although most testers cited some vibration above 6000 rpm. We don't believe anyone will find much to object to, however, since it is certainly smoother than other in-line fours and only vibrates when you are going too fast to notice. Though some small jolts do reach the arms, the ride was generally quite compliant, notably so over large bumps. With everything backed down to soft, suspension compliance is better than on almost any sport bike currently available.

The fairing, comprised of an ABS upper section and PBT bellypan, offers very little wind protection for the rider. Only the chest is shielded from the air stream. The head, neck, shoulders, arms and most of the legs are out in the wind. However, the fairing creates a smooth flow of air against you, which is much less noisy, annoying and fatiguing than a turbulent airflow that whips around your helmet. Although frontal area has been kept to a minimum, we aren't terribly impressed with the fairing's sleekness. While other manufacturers have mounted their headlights flush with the noses of their various fairings, Kawasaki persists in recessing the Ninja's rectangular headlight in a pocket, which at least appears to be a source of aerodynamic drag. It is a bit of styling carried over from the GPz series and seems unnecessary in light of the company's decision to separate the bike from the GPz lineup. Nonetheless, one staffer did manage to see an indicated 151 mph on a slightly downhill road, so the Ninja certainly isn't an aerodynamic disaster.

The fairing and the rest of the bodywork have been carefully wrapped around the bike to completely hide the frame tubing. What's covered is a unique structure, an assembly of three different components to connect the engine, suspension and rider. The basic frame is an arc of conventional round steel tubes connecting the swingarm area with the tapered-roller-bearing steering head. This is the foundation of the frame, which uses the engine as a structural member, eliminating the need for the weight of cradle tubes and permitting the engine to be mounted lower than if tubes were placed beneath it. The top front of the cylinder-head and the rear of the crankcase bolt to the basic frame, and tubular steel bracketry at its front supports the fairing, oil cooler and radiator. At the bottom rear of the main frame, the pivot for the aluminum swingarm passes through some pressed steel bracketry, supporting the swingarm pivot at its center. At its ends the swingarm is supported by a pair of aluminum plates which bolt to the main frame in three places each. The aluminum plates also support the mufflers and front and rear footpegs and act as the lower attachment points for the rear sub-frame. This third frame component is made of aluminum—mostly box-section tubing—and bolts to the main frame at the point where it turns down to the swingarm area. The rear subframe supports the seat, tail section, rear fender, etc.

Single-shock Uni-Trak suspension supports the rear of the bike and features the latest version of Kawasaki's rising-rate suspension linkage. The shock is located fairly low, and has provisions for adjusting air pressure and rebound damping. Both the air filler and the four-position rebound-adjusting mechanism are reached by removing the right side panel, which is retained by a single Phillips screw. The rear axle is supported in the massive swingarm by eccentric-cam chain adjusters, and the swingarm rides on needle bearings.

An important innovation is Kawasaki's Automatic Variable Damping System (AVDS) anti-dive in the front suspension, which automatically increases compression damping in response to the speed and distance of front wheel movement during suspension compression. It works in two stages, with the fork spring applying pressure and restricting the AVDS valve to increase compression damping after the fork has compressed two inches. As the fork continues to compress, the increase in damping-fluid pressure compresses and it is progressively forced open. It sounds a bit like the anti-dive system that we complained about on the Suzuki GS1150 two months ago. However, this one (except for the fact that the plumbing is rather ugly) met with acclaim from our testing staff.

"The fork feels best when it is about a third of the way through compression, and it continues to work well to full compression," say one rider's notes. "While braking over rough surfaces, the anti-dive system cuts out soon enough to allow supple response. The front end always feels glued to the ground." Another tester called it "the first anti-dive that stays out of your way."

The brakes themselves get top marks. They are very predictable and precise and require little effort to obtain maximum effect. Even on the one occasion that we got the front brake to fade (during a photo session when the rider was accelerating full-bore past the camera, grabbing a handful of brake to stop, then turning around and repeating it perhaps 120 times), it still had enough power for hard two-finger stops; the lever just moved in closer to the bar before beginning to stop the bike hard. When cool again, the brakes recovered completely. A new pattern of holes is drilled in this bike's discs, and sintered-metal pads are used for fade resistance and wet-disc braking power in wet conditions. Kawasaki uses standard single-piston, single-action calipers with the express purpose of reducing unsprung weight. You can also see weight-saving measures in the rear caliper's aluminum stay and in the absence of the covers usually placed over the rear caliper's less attractive components.

In addition to the effective AVDS, the balanced, air-assisted front fork features 38mm stanchion tubes, the biggest ever used on a Kawasaki sport bike. The tubes were set 10mm farther apart than the GPz1100's to accommodate tires even wider than the low-profile, tubeless 120/80V16 Dunlop F17 that comes on the ZX900. Rigidity was obviously a major concern in the front end. The fork sliders have large, effective axle clamps, and there is a unique aluminum fork brace styled into the front fender assembly. The brace loops around the rear of the wheel and acts as a bracket for the front and rear sections of the fender. The 16-inch tire diameter is big news in itself and has become de rigueur on serious sport bikes in 1984 to aid in responsive handling. In combination with modest wheel-base (58.8 inches) and front-wheel trail (114mm) measurements and plenty of weight on the front wheel, it makes for the most responsive, accurate-handling big bike this magazine has ever tested.

Which brings us to the crux of the matter. The Ninja's focal point is handling, and no competitive bike that we have tested to date does it better. Having ridden the Honda VF1000F Interceptor and the Yamaha FJ1100 only briefly, we aren't prepared to say that they won't equal or surpass the ZX900. In fact, we expect the Yamaha to perform quite well. The Honda, however, will have to be a radical improvement on the prototype we rode to earn membership in the same club as the Ninja.

The Ninja is the most neutral-steering 750cc or larger bike we have ridden since the Kawasaki KZ1000R Eddie Law-son Replica, but the ZX900 steers more quickly with less effort than the ELR. No bike over 700cc steers as lightly during transitions as the Ninja, which several riders said "feels like a 550." We took the ZX900 out to several twisting, narrow, bumpy roads that are full of tight back-to-back hairpins and surprise corners, the sort of road where a good 550 can usually get away from a 1000 and where the rider on the big bike has to struggle to make any time at all. The Ninja dazzled us. It flicked into corners with surprisingly little effort—especially considering the kinds of speeds it was generating. There was no sense of the bike's 550-pound heft, even when we had just climbed off one of the 550s that accompanied the ZX900 on test jaunts.

And there is more. The Ninja is stable and precise. Whether in flat-out 120-mph heart-stopping sweepers or 15-mph hairpins, it arrives precisely where you want it to go. You find yourself taking exactly the right line because the bike responds so accurately to your steering inputs, allowing you to clip apexes closer and exit turns wider than you ever dared to before. The tendency to turn in on some bikes equipped with 16-inch front wheels is nowhere to be found on the ZX900, and it is rock-steady at insane cornering speeds. It is surprising to discover that a chassis bolted together like the Ninja's could feel so solid.

We had to fiddle with the suspension some to get all the bike's handling potential. We soon discovered that the bike steered most responsively when we jacked the rear end up by increasing air pressure and let the front end settle by decreasing air pressure. However, this provided a rather harsh ride at the rear, especially over small bumps. When we reduced the height of the rear end, the handling slowed down, although there was still plenty of cornering clearance. Fortunately, Kawasaki provided a solution in the form of the eccentric rear axle carrier. As delivered, the axle is located at the top of the eccentric, presumably to keep seat height down. We turned it around so that it was near the bottom, raising the rear of the bike about 1.5 inches. With the suspension set near its minimums at both ends, we then had a nice compliant ride and completely responsive steering. Even set up this way, the bike was stable and solid in highspeed corners. In fact, when we first rearranged the axle position, we had the rear wheel slightly cocked, and the bike was still steady and wobble-free.

It's only fitting that such excellent handling be complemented by good tires and plenty of cornering clearance. The Dun-lops offer average traction when cold and stick very well when warmed up, especially at the front. Hard acceleration loosens up the rear tire, but not as much as the Suzuki GS1150, for example. The only way you can get the front wheel to give up any traction is to accelerate hard enough to lift it. If you ride very hard—and only one person on our staff rides this hard—and are familiar with a corner, you can drag the pegs and the trailing edge of the fairing's bellypan. However, you can't drag them too hard before you run out of traction. And as the black-and-white photo above shows, you are cranked waaaay over by then.

The confidence the Ninja inspires and the deftness with which it dispatches difficult cornering situations have to be experienced before you even begin to appreciate them. You immediately find yourself running into familiar corners 20 percent hotter and 10 percent more relaxed. You also get on the gas much sooner than ever before. Surprises in mid-turn are dealt with before the adrenaline has a chance to rise. Complex corners requiring tricky lines become easy, and impossible lean angles become common occurrences. You go faster than before, and you are in greater control.

Before we gush too much, we should merrtion some items we didn't like. The mirrors are located too far inboard for effective rear vision. The tool kit has no tool for the rear axle nut. Removing the fairing takes a while because it is held on by quite a few screws and has a lot of ducts attached to it. Our bike had a minor leak around one rocker shaft. We don't like the extra weight and ugliness of a separate license-plate light below the taillight The paint on the bellypan quickly chipped from pebbles. The turn signals don't seem to match the bike. The horn is pathetic.

Details drawing positive remarks include an excellent headlight that waits until the engine has been started to turn on, easy seat removal and installation, easy access to the battery and air filter, very low oil consumption and good paint. The instrumentation is purposeful, with the tach's face slightly larger than the speedo, although the speedo is still easier to read than some larger ones. There are also fuel and water-temperature gauges, although the temp gauge gives the impression that the engine is running very hot in traffic because the point where the fan turns on is at the upper end of the gauge's range. The bike ran cool at all speeds on the open road, but the fan frequently came on in traffic. However, the temperature needle never actually moved into the red overheat zone on the gauge. The fuse box has an easily accessible accessory terminal and uses the flat plug-in type fuses. A small fuse-pulling tool is even included in the fuse box. There is an extra storage compartment in the tail section and a helmet hook on each side of the bike. One of the slickest touches is a pair of fold-down bungee-cord hooks to help you avoid scratching the paint.

Everything comes together when you ride the Ninja fast. Two staffers thrive on telling and retelling the story of their ride down from the San Francisco area to Los Angeles on the Ninja and a GPz550. They took back roads (Route 25) which in the northern section are fast and swoo-py and provide hours of intense highspeed pleasure. At about dark, they turned onto a narrower, tighter, poorly maintained road, which switches back unpredictably, narrows without warning and throws potholes, off-camber corners and other obstacles at you. Soon they rode into a heavy fog and began discovering deer, cattle and other creatures on the completely unmarked road. In short, it was the kind of ride that would have been a nightmare on most big bikes and

probably would have ended with a skid on some of the plentiful sand or an excursion into some deserted pasture. However, except for wiping the water off their face shields for better vision, our guys had fun. The ZX900's responsive steering, controllable braking, confident feel and excellent headlight kept them from having a single frightening moment, even though they were maintaining an extremely brisk pace. They were even comfortable throughout the nine hours of their ride and came back singing the praises of Kawasaki's new sport bike.

They weren't alone. By the end of the test, everyone raved about it. The only thing that keeps us from insisting that all sporting riders rush out and buy at least one is that we haven't tested the Yamaha FJ1100 yet. But you may not want to wait. By the time you read this, the ZX900 should be available, and the Yamaha won't. And at $4395, the Ninja is also sure to be cheaper than the FJ. Or you could follow our lead: order a ZX900 now and think about adding a Yamaha later. The Ninja is a very exciting motorcycle, a leap forward for large-displacement sporting bikes. If you think the essence of motorcycling is the sensation of leaning into corners, you need one.

Source Motorcyclist 1984