The New 750cc Superbikes

THE NEW 750CC SUPERBIKES

CW COMPARISON

ZX-7 vs. GSX-R750 vs. YZF750

IF YOU'RE IN THE MARKET FOR A NEW SPORTBIKE, we've got good news. With surprisingly few exceptions, the level of performance and reliability offered by today's crop of sporting machines is unmatched in motorcycle history.

If the sportbike you just gotta have happens to be a 750cc repli-racer, then you’re really in luck, because three manufactures have stacked the deck with allnew or nearly new offerings for 1993. To get a handle on just how good this new generation of radical 750s perform in their natural environment, we gathered the thoroughly revised Kawasaki ZX-7, the liquid-cooled Suzuki GSX-R750 and a surprise player, Yamaha’s new-from-the-rubber-up YZF750SP, then headed for the dyno, the dragstrip and Willow Springs Raceway to answer the question riders all over the country want to know: What’s the best pure sportbike in the 750cc class this year?

First, a sidenote regarding the Yamaha. The allnew YZF750SP is intended to form the foundation for Superbike race efforts, and only 15 examples, enough to fill the AMA’s homologation requirement, will be imported to the USA in 1993. You’ll need a serious race résumé and a healthy bank account to get one. List price is $17,000—$10,500 for the bike and $6500 for the mandatory spares kit. Though it’s technically not street-legal in the U.S., we’ve included the SP in this comparison because Yamaha is expected to bring in a slightly less-radical version in 1994. Called the YZF750R, that model is currently available in Canada and Europe (see “YZF for the Road,” page 38).

On paper, these 750s match up pretty well. All are powered by liquid-cooled, dohc, inline-Four engines, and all utilize aluminum, twin beam frames. For suspension, all employ inverted fork assemblies up front and single-shock, linkage-type systems in back. All use 17-inch wheels in 3.5and 5.5-inch widths, and each routes burned hydrocarbons rearward via a 4-into-l exhaust system. From there, the differences are in the details.

Though it looks similar to last year’s model, Kawasaki’s ’93 ZX-7 has been substantially revamped. First, there’s an all-new frame, claimed to be both lighter and more rigid torsionally than last year’s frame. There’s more horsepower, too, thanks to a substantially breathed-on engine that utilizes a single-inlet ram-air system, higher compression (11.5:1), and the pistons and camshafts from last year’s limited-edition, 100-plus-horsepower ZX-7R powerplant.

The ZX-7 also offers a revised rear-suspension linkage and recalibrated suspension components, which Kawasaki says are more compliant than those fitted to last year’s machine.

Like the ZX-7, Suzuki’s 1993 GSX-R750 appears similar to its predecessor, but is in reality entirely new, designed to eclipse the performance marks set by the firstand secondgeneration GSX-Rs. Its engine is now liquid-cooled and more compact than before, thanks to a redesigned cylinder head with a narrower valve angle, a shorter crankshaft and reduced cylinder pitch. Lighter pistons, higher compression (11.8:1), reshaped intake ports and a revised exhaust system round out the major engine changes.

There’s also new bodywork, as well as a more rigid frame, which offers a .75-inch-longer wheelbase and more radical rake and trail numbers than the ’92-spec frame. Wheels, brakes and suspension are basically unchanged.

As successor to the OW01 homologation special, Yamaha’s YZF750SP is to provide the foundation for Superbike racers. As such, and like the Kawasaki 7R, the SP offers as standard equipment a host of race-spec hardware, including a close-ratio, six-speed transmission, 39mm flatslide carburetors, compression-damping adjustability at both ends, a relatively flat rear-suspension linkage ratio and a solo seat assembly.

According to Yamaha, the SP’s pressed-sheet aluminum frame is shorter and more rigid than that of the OWOl and offers a steeper steering-head angle. Wheelbase is 55.9 inches, the shortest of this group by a small margin. Rake and trail are similarly radical, slightly more severe than the geometry of the GSX-R and the ZX-7. The aluminum swingarm is heavily braced, the three-spoke wheels are lighter than the OW’s, and the brake system features a pair of six-piston front calipers that squeeze 12.6-inch rotors.

The SP’s inline-Four is a derivative of the OWOl Genesis powerplant, though it shares little more than engine cases and assorted other bottom-end parts. The 20-valve cylinder head utilizes the same size valves as the OW, though valve angle has been shallowed slightly. For added mixture velocity, intake and exhaust ports have shrunk slightly in size and are D-shaped. More changes are evident within the crankcase. Compared to the OW engine, the SP’s crankshaft has been lightened by roughly a pound, and the connecting rods, which were titanium on the OW, are now steel.

Yamaha’s ever-vigilant legal department forbade us from setting tire tread on street with the non-DOT-approved YZF-some mother-hen even went as far as yanking the tumsignals and mirrors-so our on-road riding impressions are limited to the ZX-7 and the GSX-R. On the street, at around-town and freeway speeds, you won’t confuse either of these low-bar, high-peg machines with touring bikes, though things improve somewhat at higher speeds, where the wind blast helps keep a rider’s weight off his wrists. The GSX-R engine makes power more smoothly than the ZX-7 motor, but its ergonomic layout is more radical, folding the rider’s legs severely. At least the Suzuki offers a more compliant street ride than the tautly suspended ZX-7.

In the twisties, both the GSX-R and ZX-7 acquit themselves well enough to make you forget their cramped ergonomics. The GSX-R feels especially good; its softly sprung suspension soaks up all types of pavement imperfections, its motor develops power smoothly, with plenty of zip, and its light, nimble steering characteristics allow it to be flicked into and out of comers with ease, a big plus when

riding non-familiar roads.

The ZX-7 can be hustled down a curvy backroad every bit as quickly as the GSX-R, though it takes more effort due to its heavier steering manners. The ZX’s firmer suspension components also transmit more road roughness into the chassis, but the payback is an increase in feedback; you never wonder what the ZX’s wheels are up to.

Before heading to Willow Springs, we paid a visit to the dynamometer and the dragstrip to gather performance data. On the dyno, the GSX-R surprised us with its mediocre numbers, topping out at only 95.5 horsepower, 9 down to the 104.5-horsepower ZX-7, 7 down to the 102.4-horsepower YZF. That’s also a full 9 horsepower less than the figure our 1992 air-and-oil-cooled testbike posted. At first, we suspected minor mechanical problems with our bike, but three other group.

The YZF, with its tall first gear, couldn’t be launched with authority, yet it posted a run of 11.29 seconds at 127.11 mph. That was good for third-quickest among this trio, but it’s a tenth-of-asecond and 4 mph faster than last year’s ZX-7R, which also had roadrace gearing. On top, the YZF proved all-powerful, shrieking past our radar gun at 159 mph, making it the fastest production 750 Cycle World has ever tested.

’93 GSX-R750s run on the same dyno all put out horsepower readings in the mid90 range.

Thanks to its strong clutch and excellent launch ability, though, the power deficiency hurt the GSX-R only slightly at the dragstrip, where it turned in a best run of 11.12 seconds at 123.6 mph, about equal to the time turned in by our ’92-spec GSX-R750.

Top speed was up 1 mph compared to that bike, though at 15 1 mph, the new GSX-R

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At 157 mph, the ZX-7 ran a very close second for topspeed honors, but it left the others behind at the strip, turning in an impressive 11.06-second, 127.11-mph run despite a bit of clutch grabbiness. Give the ZX the Suzuki’s clutch action, and it’s a 10-second machine.

To equalize traction on the road course, we spooned GPcompound Dunlop Sportmax radiais onto the YZF and GSXR (they’re standard on the ZX-7). As on the street, the GSX-R felt compliant and softly sprung at the track, soaking up Willow’s bumpy, rippled tarmac easily during slower going. Steering was quick and precise, the brakes worked well, and the chassis felt stable and planted up to about an eight-tenths pace. Above that point, however, chassis-stability problems emerged. The standard suspension settings, so smooth on the street, allowed the chassis to move around excessively, upsetting traction as well as the rider’s confidence.

Firming up the GSX-R’s legs helped stabilize the chassis somewhat, but the Suzuki retained its vague feel at the limit. The problem seemed two-fold: a lack of front-end feedback and a too-soft rear spring, which allowed the rear suspension to stroke through its travel too easily in fast, bumpy corners.

This kept our test riders from getting the most out of the GSX-R, and relegated it to a best lap of 1:33.1 seconds. That’s a plenty respectable lap at Willow, but was the slowest of the three bikes for the day.

The ZX-7 got up to speed quickly, and after a couple of minor rebound adjustments to the fork, we sent our fast guy out for a timed session. The ZX retained the taut feel we noticed on the street, though the firmness didn’t interfere with the bike’s cornering speed or the suspension’s ability to keep the bike’s wheels firmly stuck to the tarmac, routing a continuous stream of feedback to the rider. The ZX was also superbly planted and stable in the ultra-fast sections of the racetrack. Where the GSX-R would wallow and slide, the ZX simply hooked up and wailed through. The only negative we encountered-and a minor one at that-was the ZX7’s higher-effort steering, which made Willow’s tight sections a bit tougher to navigate than when on the GSX-R.

Fleavy steering aside, the ZX-7 posted a fast lap of 1:32.1, a full second faster than the best the GSX-R could muster. More important, the ZX-7 was easier to ride quickly than the GSX-R, feeling right straight out of the box, with a minimum of suspension fiddling.

Compared to the GSX-R and ZX-7, the YZF felt harderedged, more like an actual race machine. Its initial set-up proved overly stiff, showing almost no rear-end sack with a 150-pound tester aboard, and this fed every pavement imperfection directly into the chassis, pounding the rider. We wanted to reduce spring preload to get some movement into the shock, but noticed that the muffler was already dragging in fast right-handers. Unlike the ZX-7, the YZF has no provision for ride-height adjustment, so we shimmed the upper shock mount four-tenths of an inch higher to help keep the canister off the tarmac, then reduced spring preload to soften the rear end.

It helped. With the rear of the bike sitting higher and the shock using more of its travel, we experimented with forkand shock-damping settings until we got the chassis to work through the bumps. Once set up properly, the YZF’s ride remained taut, but its light, neutral steering, powerful, quick-revving engine and the best brake feel of the group allowed riders to cut fast laps. Like a racebike, the SP felt better the faster it was ridden, though it displayed a slight twitchiness at speed, and occasionally wanted to shake its head as it unweighted over Willow’s crowned Turn Six. Those traits can be traced to the bike’s short wheelbase and steep rake, but the nervousness hindered lap times only slightly, as the YZF was able to match the ZX-7’s quickest lap, a 1:32.1.

So, where does all this leave us? Well, the YZF is an impressive, if unobtainable, machine. If and when the R-model, with its more-userfriendly gearbox and carbs, is brought to the U.S., it should be one hell of a 750. Let’s hope 1994 is the model year that Yamaha gets its corporate act together and gives us the sportbike we deserve. For now, call the YZF the best 750cc repli-racer you can’t buy.

Which brings us to a choice between the GSX-R and the ZX-7. The Suzuki’s dyno numbers are a disappointment. As with the new GSX-R1100, liquid-cooling has not brought an increase in performance, though it should be pointed out that the new engines will undoubtedly be more durable than the old-style motors, especially when subjected to the rigors of speed-tuning. Even with its power deficit, the GSX-R wasn’t that far off the pace set by the other two bikes, and on the street its suspension was the most comfortable. Regarding its looseness at speed on the racetrack, the vast majority of street riders could ride this bike forever and not run into instability.

But the ZX-7 has no such problems. After three years of off-base suspension settings, Kawasaki has struck an ideal sporting balance between firmness, compliance and feel. The ZX is quicker, faster, better on the racetrack than the GSX-R, and easier to ride at speed. Call it the best 750cc repli-racer you can buy in 1993.

KAWASAKI ZX-7

$7399

SUZUKI GSX-R750

$7299

YAMAHA YZF750SP

$10,500