Gsx-750

GSX-750

Sweet Fifteen and counting for Suzuki's 750 Superbike

DON CANET

THERE IS A CHICANE OF CLASSIC DIMENSION AT ITALY’S MISANO CIRCUIT. Hard braking precedes the challenging second-gear right/left combo. Striped, shallow-sloped curbs grace each apex, bracketing the fine line through this black ribbon of tarmac. Like notches carved in a rifle stock, the slick, polished track surface proudly bears the scars of its victims. Just for kicks, there’s an ugly, undulating patch of bumps at the exit.

What better place for the all-new 2000 Suzuki GSX-R750 to demonstrate its enhanced agility and stability?

I joined the world’s moto-press at Misano, located along the Adriatic coast, for two days of on-track testing aboard the latestgeneration Gixxer. Flicking the 750 through the chicane never resulted in anything short of steadfast precision. Applying power at the exit often had the rear stepping out ever so slightly, yet both wheels tracked over the bumps with inseparable intimacy. In short, the new GSX-R750 is better than ever and a worthy heir to its 15-year racing heritage.

With a claimed 29-pound reduction in dry weight compared to its immediate predecessor, it’s not surprising that the latest GSX-R makes light work of Misano’s tightest curves. Of greater value than total weight loss, though, are the areas in which the ounces and pounds have been shaved. Much has gone into reducing the weight of engine internals,

'offering less mechanical friction for improved power, acceleration and fuel efficiency. While the chassis also is lightened and more compact, newly designed wheels and brake components have reduced unsprung weight and rotational inertia for better suspension response and agile handling.

It only took a lap or two to recognize some significant improvements over last year’s bike.

The abrupt

off/on throttle response experienced with the earlier fuelinjected GSX-R, introduced two years ago, has now been tamed. Engine response is more manageable-of particular importance when cracking open the throttle mid-comer, where a sudden hit of power can unsettle the chassis.

At the core of this change is an updated, state-of-the-art fuel-injection system, giving the 2000 GSX-R improved fuel efficiency, power output, throttle response and driveability. The digital ECM (Electrical Control Module) now has twice the processing speed and three times more memory capacity than last year’s bike. The ECM’s memory stores a total of eight fuel-injection and 12 ignition-timing maps plotting the ideal air/fuel mixture and spark timing for a wider range of conditions. Sensors monitoring throttle position, engine speed, gear selection and coolant temperature are factored in along with intake air temperature and air pressure-typical contemporary EFI wizardry.

Of greater innovative interest is the injection system’s secondary throttle butterfly valve arrangement. The rider controls the primary throttle butterfly valve while the ECM progressively opens or closes the secondary valve—via a servo motor and cables-to maintain maximum intake velocity.

The injector nozzles have also been angled more perpendicularly to the intake tract to improve fuel atomization.

Adopting the secondary throttle valve system eliminates the need for the airbox flapper-valve system used on last year’s bike, making it possible to more than double the air-

box intake area and slightly increase its capacity. The ram-air intake ducts have been located closer to the center of the fairing nose, which is the point of highest air pressure.

This all translates to the rider in the form of increased power output throughout the rev range (a claimed 5 percent gain) dealt out in a more linear and broader spread. Keeping the rev counter between 10,000 and the 14,000-rpm redline produced wicked acceleration off comers. On the street, I imagine that working the engine from 4000 to 8000 rpm would provide all the urge that I’d need. Cruising the track at 5000 rpm in top gear provided an

impression of 4

freeway

speeds, with only a moderate amount of vibration coming through the bars.

While roll-on

acceleration under such load might not match the best literclass machines, it’s not far behind thanks to this 750’s ultra-feathery 366-pound claimed dry weight.

Chassis-specific updates account

Chassis-specific for nearly 18 pounds in weight savings. The twin-spar aluminum frame is lighter, more rigid and compact (in height and length) compared to the ’99 model. The swingarm’s construction has been revised and is now lighter, more rigid and 20mm longer for improved traction and feel at the rear. Weight distribution is also concentrated more on the front (51.4 percent) where last year’s bike carried an equal 50/50 front/rear distribution.

A strong sprint along the Misano front straight netted two upshifts, topping fourth gear before braking for Tum 1. Taking the 90-degree right in third gear dropped engine revs to 8500 rpm through the apex. Even though the engine was well below peak power output, care was required to avoid breaking the rear tire loose as the throttle was applied off the heart of the corner-a harsh reality demonstrated by a luckless Brit journalist who high-sided in spectacular style during our second session.

Next is a short chute feeding a dogleg right, taken knee down at the top of third. The full-tilt cornering posture is held well into the braking zone that follows. New Tokico four-pot calipers (replacing last year’s six-pot pinchers) provided exceptionally progressive feel-appreciated at times like this. I was also amazed at how neutral the bike’s steering felt during the hard-braking, right-to-left transition into the sharp, second-gear curve ahead.

This begins a four-turn series of increasingly fast lefthanders leading onto the backstraight. Wayne Rainey once referred to this section as being one of his favorites in all of racing. It’s no mystery why a former AMA dirttracker would gel with this stretch of road, and the GSXR750 seemed to find the groove as well. Even mid-corner line adjustments failed to upset the chassis’ surefooted resolve. The only bit of unwanted movement came in the form of a slight wallow driving off the final bend at well over 100 mph.

After experimenting with suspension adjustments, my seat-of-the-pants feel is that the oscillation stemmed from rear-tire deflection under heavy cornering load. While stateside GSX-Rs will wear Dunlop D207 radiais, the Euro-spec

bike I rode was shod with street-compound Michelin Pilots. Bump-damping carcass flex is a typical-and desirable-trait of today’s street radiais that enhances stability and ride quality under normal road use, so criticism under race conditions is a little unfair.

Fairing wind protection was put to the test on the fast backstraight. The clear screen is just tall enough for tucking under the windblast, yet keeps frontal area to a minimum. While a much longer straight would be needed to fully stretch the bike’s legs, high-speed stability was superb at the 150 mph speeds I reached.

Aggressive straight-line braking for the ensuing secondgear sweeper offered another positive test of stability. The bike never weaved or got crossed up on the binders. Dropping down through the gears didn’t cause rear wheel hop, either. Extreme braking, here and elsewhere on the circuit, failed to bottom the 43mm inverted Showa fork. In fact, the revised legs instilled nothing short of total confidence, even when tempting the limits of traction.

Misano’s surface isn’t known for having stellar grip on a good day, let alone a cool winter afternoon. It’s no surprise that tire adhesion proved to be the bike’s limiting factor at this press launch. Breaking the rear loose in comers was a fairly common, albeit controllable, occurrence. Such conditions left untapped reserves in cornering clearance, with only the footpeg feelers kissing the asphalt.

Working the next few comers toward the chicane put the suspension to good use, soaking up mid-comer surface imperfections with abundant ease. A non-adjustable steering damper-cross-mounted in front of the steering head-quelled any hint of headshake, another area of notable improvement over its predecessor. It’s in this respect that the new bike differs most from its predecessor when ridden near the ragged edge.

I came away from the test wondering where the bike’s limits might end given the unparalleled grip of the latest race-compound skins. Perhaps special guest rider and former world roadracing champion, Kevin Schwantz, summed it up best. After cutting several hot laps aboard the new machine, he surmised that his 1988 Daytona 200 victory could have been achieved with this GSX-R750-in stock trim! E3