Suzuki GSX-R750: The First Generation 1986-1987
In the mid-1980s the Japanese got deadly serious about their sportbikes. When the 750cc size became the competition class of choice, everybody piled in, with Interceptors, Ninjas, FZs…and Gixxers, the first generation of GSX-R750 models, which have continued to this day, except that what cost $4,499 back then has a price tag of $11,699 in 2009.
Suzuki was promoting this new model as “a racebike for the street,” and understood that for every 750 that got flogged on the track, 10 or 20 more would be careening down the back roads of America with riders who were quite willing to be uncomfortable so they could boast of their possession. If not prowess, which most of these wannabe-racers lacked. The Gixxer had to be a practical instrument in terms of function and cost, but as far as the ergonomics were concerned, let the rider suffer.
With a clean sheet of paper the engineers at Hamamatsu drew up a bike that could both win races and yet be legal on the streets. Which meant it would also have to cope with the hammering of the Sunday ride. And they did an astounding job.
To no one’s surprise the 749cc engine was an in-line four, having twin overhead camshafts and four valves per cylinder. Instead of the increasingly popular liquid cooling, the Gixxer had an air- and oil-cooling system. The oversquare design, 70mm bore, 48.7mm stroke, had an 11,000-rpm redline, and to keep that cam chain running between cylinders two and three properly tensioned an idler gear was put in. To ensure that the fuel flow from the four flat-slide 31mm Mikunis was properly atomized, the company’s patented Twin Swirl Combustion Chamber design was revamped for the new 16-valve heads. The compression ratio was a hefty 10.6:1, which could mean melt-down if not adequately cooled, which is why the sump held six quarts of petroleum product.
A wet clutch and six speeds put the power out to the rear wheel, where the dynamometer measured about 80 horses. Since power means heat, the cooling of the motor was important. To assist the matter the thin, short fins (more effective at cooling than the thicker ones) had a special heat-dissipating finish sprayed on, and the fairing was designed to create maximum flow of fresh air. More important was a little trickery inside the engine, an extra oil pump which sprayed cooling oil on hot spots like the undersides of the lightweight pistons and on the heads, keeping the valves and camshafts at a tolerable limit. Extra oil and radiator and pump all added to the weight, but Suzuki claimed the engine package weighed only 148 pounds—Wowzer! Suzuki engineers were obviously working on improving the horsepower-to-weight ratio, as the previous air-cooled, 16-valve engine in the 1980-1985 GS750/700E weighed a good 30 pounds more.
The header pipes were of single-wall construction, to save weight, and merged into a single large muffler. Six speeds in the gearbox had fairly close ratios.
The frame was made of aluminum, with the rear section welded on. Racebikes had been using aluminum for years, but steel was the metal of choice in order to put a street-going motorcycle on the market at a competitive price. Suzuki chose to use a casting process to make the most complicated pieces, especially that around the steering head. Then the other bits could be jigwelded into the double-cradle perimeter design, saving labor costs. It weighed less than 20 pounds and was very stiff, which, while good for high speeds, meant that the casual street rider was in for a mild surprise when he or she wanted to amble through town.
A 41mm center-axle Kayaba fork was bolted on with a serious rake of 26 degrees (trail of 4.2 inches). As one tester put it so well, such steepness does “not respond well to the hand of inexperience.” The fork came with spring preload adjustment and a shade over 5 inches of travel. Suzuki claimed that the new fork, using bigger but thinner tubing, was more than 20 percent lighter than before. Anti-dive units were popular back then, and the Gixxer got one, a new design which functioned when there was sufficient speed generated by the aluminum fork sliders. At the back the single shock had adjustments for preload and rebound damping, and allowed 5.3 inches of wheel travel. The shock offered a rather sharp rising rate, good for carrying passengers, but which would probably be changed by anyone wanting to go on the track. The aluminum linkage was hooked to an aluminum box-section swingarm.
Suzuki had not gotten swept up in the 16-inch-front-wheel trend that was so popular, staying with cast-aluminum 18-inchers fore and aft. Of minor interest to those fascinated by the subject of wheel size, on the second-generation GSX-R750 the wheels were 17-inchers. The front rubber was a 110/80, the rear, 140/70. Brakes were ferocious, with opposed four-piston calipers on the two front discs, a smaller disc with a two-piston caliper at the back.
Light is good. Suzuki put the whole concept on a Jenny Craig program, with the detail guys hollowing out bolts to save a few grams. Wet weight was an astounding 465 pounds, with five and a half gallons in the tank—divide that by the 80 horses, and that is 5.8 pounds per horse. Tough to beat.
Small size can very be good. The alternator was mounted behind the cylinders to keep the crankcases as narrow as possible, assist cornering clearance and shorten the entire bike. The Gixxer could cheerfully reach 55 degrees of lean, if the rider had the courage to defy the forces of gravity, which was great on a track, rather scary on a public road. This meant the footpegs had to be rather high up, so bendability was a key to rider happiness. Wheelbase was a very short 57.3 inches—this on a bike with passenger seat and pegs. Top speed? One-hundred, forty-five mph, depending on who was riding.
Then in 1988 an entirely new Gixxer appeared, same basic design but new frame, even more oversquare engine (73mm x 44.7mm = 748cc), and 90 horses at the rear wheel. And more money: $5,199.
(This Retrospective article was published in the December 2009 issue of Rider magazine.)