Suzuki GSX-R 750WP

Suzuki decided not to bring its new liquid-cooled GSX-R750 repli-racer into the U.S. this year because its air-and-oil-cooled 750 continues to offer class-leading performance at a reasonable price. Even though the new 750 is for sale in Canada, Europe and Australia, Suzuki felt that introducing a more expensive GSX-R to the soft American market would unnecessarily alienate cost-conscious buyers.

Next year should be a different matter. The current U.S. GSX-R engine-in its seventh year of production-is showing its age. Fine for street use, the air-and-oil-cooled motor has trouble dissipating heat when modified, which has led to engine failures in competition. Introduced in 1985 as a road-racer for the street, the GSX-R750 no longer is a threat on the racetrack, an untenable marketing position. Also, industry grapevines are alive with the rumors that Honda, Kawasaki and perhaps Yamaha are poised to introduce updated 750s. Clearly, to stay in the hunt on the racetrack and in the showroom, Suzuki has to bring the liquid-cooled 750 to the USA in 1993.

In anticipation, Cycle World jetted to Canada to test the latest GSX-R750 at Shannonville Motorsports Park, located about 115 miles northeast of Toronto, Ontario. We borrowed two GSX-Rs-a liquid-cooled 1992 model and, for comparison purposes, an air-and-oil-cooled 1991 version, identical to the '92 U.S. model. Cycle World, a Toronto-based Suzuki dealer, and Cycle City, a Burlington, Ontario, Suzuki/Yamaha dealer, loaned us the bikes, while Competition Systems of Markham, Ontario, provided track-side support.

Almost 3 quarts of coolant circulate through the engine and a curved, 13-by- 15-inch radiator, pushed through the engine's water jackets by an externally mounted waterpump driven from the oil-pump shaft. Suzuki says that optimal operating temperature is 170 degrees Fahrenheit, and that an electric fan switches on if coolant temperature reaches 220 degrees.

Thanks to the new cooling system, the engine's oil is called on to handle less of the heat-dissipation chores, so a single-stage oil pump replaces the dual-stage unit used on previous GSX-Rs. Gone is the oil radiator; engine oil now passes through a liquid-cooled oil cooler built into the oil-filter base. As with previous designs, though, oil is sprayed on the undersides of the pistons. Suzuki claims a combined cooling capacity twice that of the old powerplant.

The oversquare, 70.0 x 48.7mm bore-and-stroke dimensions of the previous engine have been retained, as have 38mm Mikuni CV carburetors, although the new bike's carbs don't include the powerjet circuit used on later GSX-R750s. As on the GSX-R600, Suzuki adopted a shim-under-bucket valvetrain design for the 750, which allows the camshaft lobes to act directly on the valves without the use of rocker arms, resulting in better valve control at high rpm. Valve-adjustment intervals have been increased from 3500 to 7500 miles, and the traditional 600-mile valve-lash service has been eliminated.

Included valve angle has been reduced to 32 degrees from the previous motor's 40 degrees, and the compression ratio is up from 10.9:1 to a sky-high 11.8:1. The new 750 uses lighter pistons and narrower-stemmed valves, with intake tracts that have been reshaped and shortened. And the cam timing, the carburetor jetting and the 4-into-2-into-l exhaust system all have been revised.

This new motor also is substantially smaller and more compact than previous GSX-R designs. The crankshaft has been shortened, cylinder pitch has been reduced, and the starter clutch has been relocated to accompany the alternator behind the cylinders. The new cylinder head-which still utilizes Suzuki's Twin Swirl Combustion Chamber-is smaller as well, thanks to the tighter valve angle, narrower cylinder placement, more compact valvetrain, shorter camshafts and elimination of two camshaft journals, one per side.

With a more compact powerplant, Suzuki was able to relocate the engine farther forward and lower in the chassis. This improves front-wheel weight bias and lowers the bike's center of gravity without sacrificing cornering clearance.

Like the engine, the chassis has been thoroughly revised, though the similarity in appearance to previous GSX-RS was maintained. The aluminum, double-cradle frame now features pentagonal-cross-section main spars, which, according to Suzuki, increase torsional rigidity by five percent. The asymmetrical aluminum swingarm also is new and is claimed to be more rigid than its predecessor. Following grand prix fashion, the arm's right side is arched, allowing the exhaust canister to be tucked in tighter for additional cornering clearance. To ease maintenance and crash repair, the aluminum rear subframe, previously welded on, is now removable.

Compared to the old 750, steering geometry has been quickened by reducing rake to 24.5 degrees from 25.5 and shortening trail to 3.7 inches from 3.9. Some of the highspeed stability that might have been lost as a result of the quicker geometry has been retrieved by lengthening the bike's wheelbase 0.75 inch. A non-adjustable hydraulic steering damper helps guard against headshake.

The 750's suspension mirrors that found on the GSX-R600. A fully adjustable, inverted, cartridge-style 41mm Showa fork is mounted up front, while a Showa shock with similar adjustments and a remote reservoir is fitted at the rear. Both fork and shock springs have been altered, as have the fork's damping rates. In addition, the shock linkage has been revised for more progressive action. Tires are Dunlop D202 Sport Radials in 120/70ZR17 and 170/60ZR17 sizes mounted on 3.5- and 5.5-inch wheels, respectively.

Enough about the bike's mechanical makeup; we traveled 2100 miles to see what this new GSX-R is like to ride, especially around Shann4onville's twisty, bumpy road course. But first, to get to the track, we had to complete a two-hour freeway drone, during which the new GSX-R reminded us of the GSX-R600. Both have uncompromising seating positions, near-vibration-free engines and taut-feeling suspensions.

Like the 600, the new 750's seat-to-handlebar distance has been increased, while the seat-to-footpeg measurement has been taken in. You won't be doing much casual touring on this 750. The engine warms quickly and the bar-mounted choke can be thumbed off within a half-mile. Vibration is almost non-existent below 7500 rpm, with only a slight buzz felt through the clip-ons and footrests. Above that mark, vibes increase a bit, but are never obtrusive.

At Shannonville, we tested the two GSX-Rs back-to-back, and the results were surprising. In 40-to-60-mph top-gear roll-ons, the year-old model smoked the liquid-cooled bike by a full second, likely due to its crisper bottom-end carburetion. In the 60-to-80-mph runs, the tables were turned, with the '92 model overcoming its 3800-4200 rpm lean spot and recording a slight advantage over the air-and-oil-cooled bike. But quarter-mile acceleration again went to the '91 GSX-R, which outgunned the '92 by over a tenth of a second (11.37 seconds at 116 mph compared to 11.51/117). At first, we thought the new bike's performance dip could be attributed to its marginally taller final gearing, but a check of the charts showed that the two bikes' overall gear ratios

Suzuki claims 118 horsepower at the crankshaft for the new engine. We were unable to perform our normal dynamometer testing in Canada, but Cycle Canada magazine had just finished its road test of the very GSX-R we were riding, and it recorded 100 horsepower at 10,800 rpm, with a torque peak of 51 foot-pounds at 9000 rpm. This was on a Dynojet rear-wheel dyno, the same kind of dyno Cycle World uses. The 1992 U.S. 750 we tested earlier this year put out 104.5 horsepower and 54.8 foot-pounds of torque. Taking into account the variables of different dyno locations on different days, it is nonetheless apparent that the liquid-cooled GSX-R is no more powerful than the air-and-oil-cooled unit it replaces.

At least the new motor pushes the aerodynamically cleaner liquid-cooled GSX-R to impressive velocities. Cycle Canada radar-gunned our test Suzuki at 158 mph. That's 8 mph faster than the U.S. version, and easily makes the GSX-R the fastest production 750 to date. In fact, it's only 1 mph slower than the 1992 GSX-R1100.

Throughout the day, engine temperature remained moderate, the gauge's needle never passing halfway in the normal operating range. Competition System's Mike Crompton noted that the new cooling system works so well that Canadian race tuners have been taping over portions of the radiator in an effort to increase engine temperature.

Steering was precise and required less effort than the old-style model. Even with the reduced steering-head angle, the new GSX-R felt more stable than last year's bike, especially under hard braking. Fork action was near faultless, allowing the front wheel to track beautifully over Shannonville's many ripples. The shock, however, wasn't quite up to the same high standards. After a full day of riding, rebound damping faded to the point that the adjuster had to be cranked up to the maximum of its four settings. Racers will likely replace the damper with an aftermarket unit; most street riders will be happy with the stock setup.

Though the rear suspension's damping qualities left something to be desired for hard riding, we found the revised rising-rate linkage to be a real improvement. Last year's design offered softer initial reaction to bumps, but became suddenly harsher farther into the travel. The new link is more linear and provides a more compliant overall ride.

The Nissin four-piston calipers and 12.4-inch discs also performed well, offering consistent, fade-free stopping. The 9.6-inch rear disc and its twin-piston caliper, though, were overly sensitive and caused the rear tire to chatter under hard use. The stock Dunlop D202 Sport Radials, though not the company's premium-grade sporting rubber, worked well at Shannonville, and only began to lose their grip late in our track session. And even then, slides were very predictable and easy to control.

Is the liquid-cooled GSX-R the ultimate 750 sportbike? Tough question. Its. chassis is first-class, no doubt, but the new engine is no more powerful than the previous air-and-oil-cooled design. And though Suzuki should be commended for adding liquid cooling without increasing weight (we didn't have access to a scale in Canada, but the bike should be very close to the old-style's 484-pound dry weight), the latest-generation GSX-R tips the scales with about 60 more pounds than the original 1985 GSX-R750. Not very impressive in this post-CBR900RR era-the new Honda weighs-in at 432 pounds dry.

But the good news is that the liquid-cooled bike has a better chassis and is better-handling than the old bike. And, more importantly, the cooling system seems to have been overengineered for street use, which means race tuners should be able to tweak the motor to their heart's content and not worry about burning the thing down to its base gasket. Factor in the more slippery bodywork, and Suzuki should once again be a force to be reckoned with in production-based roadracing.

There's more good news on the price front. Despite American Suzuki's early fears that the liquid-cooled bike would be overpriced, it is currently on sale in Canada for the equivalent of $6800, just $100 more than the U.S. air-and-oil-cooled version. Even if a few hundred more dollars get tacked on for 1993, Suzuki shouldn't suffer in the showroom.

So, this newest GSX-R offers no great technological leaps forward. But for Suzuki, it is a very big step in the right direction.