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The Subtle Art of Suzuki’s 2000 GSX-R750 – Part Two

The first hint that Suzuki placed function over form in its redesign of the GSX-R750 is the size of the rear wheel and tire. While every other manufacturer is going to a larger rear wheel and tire (190 section tires are the fashion — with the the Kawasaki ZX-12 getting a 200 section rear), Suzuki made its rear wheel smaller (now a 5.50 x 17, rather than a 6.0 x 17) and its rear tire smaller (now a 180 section, rather than a 190 section). Big deal, you say? Your damn right it’s a big deal.

A fat rear tire is a big selling point. While all of you gearheads out there sweat the details, many sportbike riders are swayed by looks more than anything else, and a fat rear tire sells on the showroom floor. The fact that Suzuki not only resisted the temptation to go with a larger rear tire, but reduced the size of its rear wheel and tire for 2000 speaks volumes about Suzuki’s commitment to performance.

A smaller rear tire and wheel (1) weighs less (obviously), and (2) allows for a quicker turning motorcycle (all things being equal except the tire). While other manufacturers are starting with a fat rear tire, and engineering the chassis around it (or at least making adjustments to make the motorcycle turn quicker despite the big rear tire), Suzuki’s engineers won out over the marketers. When a manufacturer resists a stylish trend such as this, you know it puts performance first. The rest of the motorcycle reflects this same thinking.

While many other manufacturers have yet to introduce fuel injection on their sportbikes, Suzuki has the luxury of bringing to market a second-generation fuel injection system with the 2000 GSX-R750. If Suzuki’s claims for this system are accurate, this could be the single most impressive development on this bike. Claiming an innovative fuel injection design which delivers “massively improved throttle response”, Suzuki’s press material painstakingly explains its new development.

Comparing its fuel injection advancement to the development of the constant-velocity carburetor, which smoothed off/on throttle response, particularly at low rpm’s, Suzuki touts its system as the first motorcycle fuel injection design to maintain intake velocity during off/on throttle transitions, thus avoiding the jerky, sudden power delivery associated with many fuel injection systems manufactured by rivals.

If you think smooth throttle response is not a big deal, you probably have not ridden a modern, fuel injected four-cylinder motorcycle. Throttle control must be much more precise on such a machine. Suzuki’s system, controlled by a 16-bit digital engine management CPU, employs a secondary butterfly valve in each throttle body to smoothly and progressively open at pre-programed engine rpm and gear positions when throttle is applied — in order to maintain maximum intake velocity and avoid the jerkiness and suddenness associated with other fuel injection systems.

If Suzuki’s system works as advertised, the new GSX-R750 will be far easier to ride, and will instill much greater rider confidence. Why? Because seamless power delivery increases predictability and rider control, and, moreover, the high-side is the worst accident in motorcycle racing (not to mention street riding — where a high side is the worst single-vehicle accident short of running into a brick wall). A high-side is typically caused by sudden acceleration when exiting a corner which causes the rear end to slide out before, just as suddenly, regaining traction and catapulting the rider over the bars.

Suzuki’s system would significantly reduce the possibility of a high-side by allowing the rider to more confidently and smoothly apply power upon exiting turns (while the bike is still leaned over). It will also make for an overall smoother and better controlled ride, both on the street and on the track. As an added benefit, Suzuki claims this system is responsible for increased low-rpm and mid-rpm torque.

This latter point regarding low and mid-range torque is important. The GSX-R750 has been lacking this for several years, and has a well-deserved reputation for a peaky power output. Even the newer 600′s seem to have more torque around town at lower rpm, and are more rideable and smooth in their power delivery. If Suzuki has made a significant step forward in the low to mid rpm power delivery, the new GSX-R750 will be a far superior street bike.

The thoroughness of the fuel injection design is carried over to the engine itself, which is more than 11 pounds lighter, 15mm shorter front-to-rear, 8mm narrower and with 4mm less height. The engine is virtually all new, and this weight savings is dramatic given the relatively compact and lightweight design of the 1999 engine.

The 11 pound reduction was achieved through painstaking analysis and refinement, saving a few ounces here and an ounce there. With modern computer analysis as an aid, Suzuki attacked virtually every component of the engine, reducing sizes and wall thicknesses where safe to do so. It also employed magnesium in several places (including the cam, clutch, starter, alternator, and counter-shaft sprocket covers). Additionally, the entire oil pan is magnesium. A one-piece casting of the cylinder block and upper crank case, as well as the internalization of oil hoses resulted in significant weight savings, as well.

Re-positioning of the aluminum water-to-oil cooler (which was previously steel) allows the exhaust headers to be tucked in tighter to the engine for improved mass centralization and engine packaging.

The redesigned engine, in addition to the improved throttle response and increased low and midrange torque, provides six additional horsepower according to Suzuki. Suzuki claims power output is increased throughout the rpm range, and not just at its peak.

Suzuki also claims that the 2000 GSX-R750 employs a dramatically improved balance of frame rigidity, weight placement, swingarm length and rigidity, and overall chassis geometry — much of it derived from testing and development of Suzuki’s 500 GP bike (piloted to victory at more than one GP this year by Kenny Roberts). As with its rear tire size, Suzuki countered a design trend by increasing (rather than decreasing) the wheelbase of its 750. The wheelbase is significantly longer (6/10ths of an inch longer or 15mm) than the 1999 model. Coupled with a 20mm longer swingarm placing significantly more weight on the front wheel, Suzuki claims to have improved both turning ability and straight-line stability.

Of course, like other superbike competitors, the new GSX-R750 has spent time in the wind tunnel, resulting in reduced frontal area and a lower coefficient of drag. The design of the fairing also maximizes rider wind protection and increases the effectiveness of Suzuki’s RAM air system.

Suzuki reduced the number of pistons employed in its front brake calipers from six to four, and dramatically reduced the weight of these calipers without affecting break performance. Indeed, some of the best brakes in the world (including racing Brembos and Yamaha R1 calipers) are four-piston and not six-piston brakes.

Suzuki’s GSX-R750 is the ultimate production roadracer. A claimed 66 pounds lighter than Honda’s production superbike, the RC51, the GSX-R750 literally needs nothing to hit the track. Already near the weight limits imposed by several racing classes, the off-the-rack GSX-R750 is a titanium exhaust and single-seat unit away from a sub-350 pound dry weight. Incredible. (As a side note, the Honda CBR929RR comes with a stock titanium exhaust system, and the GSX-R750 is therefore capable of a much greater weight savings with an after-market exhaust replacing the stainless steel stock system).

600cc sportbikes are frequently the fastest street legal machines around a race track. The open class bikes, despite (or because of) their superior power-to-weight ratios, are simply too intimidating and hard to control. A 750 might be the perfect compromise, and Suzuki’s GSX-R750 will be a real hit if two areas have been addressed by Suzuki.

The power delivery of the GSX-R750 must be improved at low and mid rpm’s for the bike to be a superior every-day street ride compared to Honda’s CBR600F4, for example, which has a much more pleasing around-town throttle response. Second, the “twitchiness” of prior GSX-R750 chassis designs can be annoying both on the street and on the race track.

Suzuki claims to have addressed the low to mid rpm power-delivery problem, and improved stability in the longer-wheelbased year 2000 model. If so, the 2000 GSX-R750 just might be the “Holy Grail” of sportbikes. We will find out in a few months.