Game Changer: 1986-1987 Suzuki GSX-R750
Years produced: 1986-1987
Power: 106hp (claimed), 79hp @10,500rpm (measured RWHP)
Top speed: 142mph (period test)
Engine: 749cc (70mm x 48.7mm) air/oilcooled, 16-valve DOHC inline four
Transmission: 6-speed, chain final drive
Weight/MPG: 388lb dry (claimed); 465lb w/full tank (period test)/35mpg (avg.)
Price then/now: $4,499 (1986)/$3,000-$6,500
“Sportbikes will soon be divided into two categories: before the GSX-R and after,” gushed Cycle World in March 1985 of Suzuki’s new hyper bike.
What made it so special? It was the lightest bike in its class by a country mile. When Cycle magazine compared the latest batch of 750s in July 1986, they recorded full-tank curb weights of 505 pounds for Honda’s VFR750, 524 pounds for Yamaha’s FZ750, and just 465 pounds for the Gixxer. Suzuki claimed a dry weight of 388 pounds versus 489 pounds for the GS750 it replaced, the engine alone being 24 pounds lighter.
Designer Etsuo Yokouchi was obsessed with minimizing mass, so he decided on air/oil cooling rather than adding water jackets, a radiator and a pump. By 1986, though, he was swimming against the tide. The Other Three had all switched their premium 750 sport bikes to liquid cooling. Yokouchi chose instead to rely on a high-volume, low-pressure pump to circulate up to 10 liters of oil per minute through the cylinder head, using fins and a king-size oil cooler to dissipate heat. Bottom end lubrication and piston-cooling oil jets were fed by a conventional high-pressure pump.
Though based on the GS, the GSX-R engine used lighter components throughout. A bore increase from 67mm to 70mm and shorter stroke allowed higher revs for the same piston speed, and larger valves for more power. Dual overhead camshafts were driven by a central chain and the cam box was capped with a magnesium cover. Four 29mm Mikuni carburetors fed revised 4-valve Twin Swirl Combustion Chambers (TSCC), with a 4-into-1 exhaust. Drive to the 6-speed transmission was by straight-cut gears and a wet multiplate clutch.
Yokouchi’s minimalism extended to the lightweight aluminum tube frame, which owed much to the GS1000R endurance racer. It featured Suzuki’s Full Floater single-shock rear suspension (adjustable for preload and rebound damping), aluminum swingarm, and preload-adjustable 41mm Kayaba front fork. Eighteen-inch cast aluminum wheels with triple disc brakes ran on radial tires.
So how did the GSX-R stack up against the competition? Though the lightest of the 750 superbikes, the Gixxer was also the least powerful, recording 79.26 horsepower on Cycle’s dyno, while Honda’s VFR clocked 82 horsepower and Yamaha’s 5-valve FZ topped 85. On the strip, though, the bikes performed similarly, with all three in the 11.1-second range at around 121mph for the standing quarter in Cycle World‘s comparo. The same magazine took the 750s to Willow Springs Raceway: Though the Gixxer recorded the slowest time, testers blamed a flaccid stock rear shock and recommended an aftermarket replacement.
Suzuki had established a reputation for quality and durability with their air-cooled fours. Would the extra performance and lighter weight of the GSX-R750 come at the cost of reliability? Cycle World took a couple of Gixxers to Uniroyal’s 5-mile banked test track in Laredo, Texas, and ran them for 24 hours, setting a new endurance speed record, averaging 128.3mph including fuel and tire stops.
Taking it to the street, Cycle World found the GSX-R was “wonderfully competent in most performance categories,” but cautioned, “It simply is not a very good street bike.” Cycle magazine concurred: “The seating position that lets the Suzuki work so well at the racetrack and in the canyons cannot translate comfortably to highway use. Arms tire quickly, legs cramp up,” they said. Cycle World‘s testers also found the bars too low, the pegs too high, and the steering heavy with the narrow clip-on bars. “The Suzuki’s top-weighted powerband requires concentration on gear selection as well,” they said. Cycle magazine’s tester perhaps summed it up best: “Suzuki’s new GSX-R750 is a race bike with lights.” Ergonomics aside, Cycle magazine strongly endorsed Suzuki’s approach to avoirdupois, noting that lighter weight also meant other major components — suspension, brakes, drivetrain — were less stressed. “The Suzuki GSX-R750 is running proof that validates the low-mass approach to high-performance motorcycling,” they said. Its significance in sportbike development was also recognized by Cycle Guide, which awarded it Motorcycle of the Year in 1987. MC
Contenders: Sporting Alternatives to the first GSX-R
1985-1991 Yamaha FZ750
Years Produced: 1985-1991
Power: 85hp @ 11,500rpm (period test)/140mph (period test)
Engine: 749cc liquid-cooled 20-valve DOHC inline four
Transmission: 6-speed, chain final drive
Weight/MPG: 524lb (wet)/30-50mpg
Price then/now: $4,599 (1985)/$1,500-$4,500
Were five valves better than four? Yamaha thought so, fitting three intake and two exhaust valves to its FZ750. The 20-valve Genesis engine churned out 85.3 horsepower at 11,500rpm on Cycle‘s dyno. It also tore up the quarter-mile strip in 11.4 seconds at 117mph in their 1985 test. “It’s hard to conceive of this level of power from an over-the-counter 750 engine,” Cycle‘s editors said, adding, “The engine is remarkably tractable, too.”
The drivetrain slotted into a square-section steel tube perimeter frame with the cylinders canted forward at 45 degrees. An air-adjustable Kayaba front fork with 39mm fork tubes controlled the 120/80 x 16-inch front tire by a steep 25.5-degree rake, while a single, multi-adjustable spring/damper unit and swingarm held the 130/80 x 18-inch rear. Triple discs provided braking.
Cycle Guide‘s tester found that, in spite of the steep steering angle and 16-inch front wheel, the FZ750 was slower to turn at moderate speeds, but was more nimble when pushed hard, and had “rock-solid stability.” Testers also found the FZ’s handling to be sensitive to front fork air pressure, rear preload/damping settings and tire pressures. Said Cycle, “(The FZ750) offers class-leading horsepower and possesses superb handling as well as composure and feel.”
“It’s the blueprint for sport bikes of the future,” concluded Cycle Guide.
1986-1989 Honda VFR750F
Years produced: 1986-1989
Power: 106hp (claimed), 82.5hp @ 10,500rpm (measured RWHP)/144mph
Engine: 748cc liquid-cooled 16-valve DOHC 90-degree V4
Transmission: 6-speed, chain final drive
Weight/MPG: 505lb (wet)/33-55mpg
Price then/now: $5,298 (1986)/$1,500-$4,500
Though derived from the 1983 VF750F, Honda’s 1986 VFR750F was pretty much all new — except the bore and stroke. The most significant change was from chain-drive to gear-driven cams, intended to assure punters that the valvetrain issues of the VF750 would not recur.
The new engine was physically smaller, lighter, more powerful (thanks to better breathing), and more reliable because of improved oiling and revised valve operation — each valve was opened by its own cam lobe and rocker versus the paired setup on the earlier engine. The transmission went from five gears to six. The revised drivetrain went into an aluminum perimeter beam frame (instead of steel on the VF) as a stressed member. The chassis was fitted with an anti-dive fork with 110/90 x 16-inch front tire and adjustable single-shock swingarm with a 130/80 x 18-inch rear tire.
The new VFR became the pacesetter in its class, recording a best standing quarter in the low 11s at 120mph in Cycle Guide‘s test. It was also fastest around Willow Springs in Cycle Guide‘s 750-class comparo. The same magazine called it “the best sporting 750 in the world,” awarding it Motorcycle of the Year for 1986.
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