The New Superbikes

THE NEW SUPERBIKES

CYCLE WORLD TEST

HOT DAMN! Never before have we had three such exciting motorcycles together for a test. These are the fastest, best handling, most spectacular 750s made. The creme de la creme. Together. Head to head. Just as this year's Superbike races will pit this Honda V45 Interceptor, Kawasaki GPz750 and Suzuki GS750 against each other, we'll run them against each other and against the clock.

Collectively, these are motorcycles that can blitz through a quarter mile in 11 sec., go faster than 130 mph and slice the heart out of a corner. All of these motorcycles are derived from earlier 750s, but mostly they are new. They all have single shock rear suspensions, with aluminum swing arms connected to adjustable shocks through progressive linkage. Two of these bikes are the first attempts by their factories to build single shock street bikes. Two of them have 16 in. front wheels. All of them have superior tires, suspensions and motors.

Three bikes. Eight camshafts. 40 valves. 257 horsepower. Power, they have. Perhaps more important than the power, is how useable it is. Bigger motorcycles may have even more power, but that doesn't mean a bigger bike can go faster. On the kinds of roads that attract motorcyclists, these 750s can be ridden harder, and with less effort, making them more fun.

Visually, these motorcycles are as thrilling as they are to ride. One is a bright, eyepiercing red. Another is silver with blue accents. The other is blue and white, with a silver frame. No wallflowers here.

Everything about these bikes is strong. Their performance, their styling, the impact they leave on riders and the message they leave for other riders, all this says these are the best sports bikes made.

HONDA INTERCEPTOR, KAWASAKI GPz750, SUZUKI GS750E... HOW THE NEW SUPERBIKES MATCH UP

HONDA INTERCEPTOR

Skeptics the appeal who on accuse a Certain Honda American of trying Brand too hard need to cash only in look on at the Interceptor to know how far and how fast in any direction Big Red can move when opportunity presents itself.

Contained in this striking package are lines of thought directly descended from the experimental NR500, the in-production V45 Sabre and Magna, the not-sold-here CB1100R and the racing-only FWS.

The Interceptor is beautifully integrated. As the detailed description shows, the frame and engine and front wheel and suspension and fairing and radiators could only work with each other while no one part can be singled out as the point at which the other partners in the project begin to earn their keep.

Well, maybe the engine.

The general principle appeared in 1982, with the V45 Sabre and Magna. Like that engine, the V750F Interceptor is a 90° VFour, with a bore and stroke of 70 x 48.6 mm and a displacement of 748cc. The engine is water-cooled with cylinder liners cast into the upper crankcase, has double overhead camshafts working four valves per cylinder and a 10.5:1 compression ratio. The crankshaft rotates in plain main bearings. Each pair of 26mm intake and 23mm exhaust valves operates off a single cam lobe via a forked follower arm with screw-type adjustment for clearance. Valve included angle is 38°, which gives good flow while not masking the ports or limiting the compression ratio. The Interceptor uses the same valve timing as the V45s.

The Interceptor engine, though, isn't interchangeable. The engine mounts are solid, not rubber. Final drive is chain, not shaft, and while the cylinder banks are 90° apart the vee has been tilted up and back in order to shorten the drivetrain. The Interceptor's front cylinders are angled 30° from horizontal while the Magna/Sabre’s front cylinders are 23.5° from horizontal. The relationship of the crankcases to horizontal is the same: the Interceptor’s crankcase castings are changed.

Those crankcases hold a five-speed transmission with the overall fourth/fifth ratios more closely-spaced than the overall fourth/fifth ratios found in the Magna/Sabre's six-speed transmission. The Magna/Sabre’s sixth gear is very tall and drops rpm to about 3800 rpm at 60 mph. The Interceptor’s overall fifth is very close to the Magna/Sabre’s fifth and since the Interceptor doesn't have a sixth gear for cruising sedately, its engine turns much faster at 60 mph, 4700 rpm.

The Magna/Sabre engine has three gear reductions in the powertrain, not counting the transmission (crank to clutch, transmission output shaft to driveshaft, driveshaft to rear wheel) and the crankshaft spins opposite wheel rotation. The Interceptor has just two reductions other than the transmission, (crankshaft to clutch, transmission output shaft to rear wheel) and the Interceptor engine spins in the same direction as wheel rotation. The Interceptor’s clutch basket is split vertically, the two halves joined by a one-way (sprag) clutch. The sprag clutch isn't noticed in normal riding, but faced with clumsy or rapid downshifts, it disengages half the clutch plates, reducing the tendency of the rear wheel to lock or hop. The Interceptor clutch has one large diaphram spring. Like the Magna/Sabre clutch, the Interceptor clutch is hydraulically operated.

Honda claims almost six more horspower for the Interceptor engine, 86 bhp at 10,000 vs. 80.3 bhp at 9500 rpm for the Magna/Sabre. The extra power, Honda engineers say, came from changes in the airbox. The Interceptor airbox is larger (6.5 liters capacity to the 1982 Sabre’s 6.2 liters and the 1982 Magna's 4.3 liters) and inducts cool air from above and forward of the cylinders instead of taking heated air from between the cylinder banks.

Worth noting here are the Interceptor’s connections to Honda’s world-wide racing efforts. The emphasis on increasing horsepower with cold-air induction was seen on the NR500, as ridden by Freddie Spencer in 1981, although the racebike didn’t have a sealed airbox and air filter. A whole series of other Interceptor features were developed on Honda’s racebikes. Consider the frame: two sets of widely-spaced rectangular steel tubes run from the well-braced steering stem, one set running around the top of the engine, the other running around the bottom of the engine. Sub-frame tubes run back to hold the top of the single rear shock and the seat section, and the gas tank fits on top of and inside the frame tubes.

Like the Magna and Sabre frames, the Interceptor frame has a section of left downtube that unbolts to ease engine removal and installation. But unlike the Magna and Sabre, that tube doesn't carry coolant from the water pump to the radiator, a rubber hose with a protective spring cover does that. The Interceptor has two radiators, one mounted on the downtubes above the forward cylinder head with two direct-drive electric fans behind it, the other mounted inside a plastic cowling under the forward cylinder head with no cooling fan. Replacing the Magna/Sabre’s single large radiator with two smaller radiators worked together with the tilted cylinder banks and 16-in. front wheel to move the front wheel closer to the frame, reducing wheelbase to 59.8 in. from the Sabre’s 61.8 in., without clearance problems. The two radiators are also narrower than the single, larger radiator, reducing frontal area.

The swing arm is a hollow aluminum sand casting and pivots on a single needle bearing on the left side of the swing arm, and two side-by-side ball bearings on the right. The ball bearings handle side loads experienced during cornering. The swing arm is connected to the rear shock by levers, making suspension action progressive.

The Showa rear shock uses a large coil spring and air pressure, which can be adjusted over a range of 7 to 43 psi. Four rebound damping settings, each numbered, each produce 25 percent more damping than the one before it. Compression damping is fixed. The shock air fitting is located under the snapon left sidecover and the rebound damping adjustment lever is

on top of the shock body, under the locking seat.

Showa center-axle forks are held by a forged aluminum upper and a steel lower triple clamp. The steering head uses tapered roller bearings. Rake is 28°, trail 3.9 in. The forks have 39mm stanchion tubes (the 1982 Sabre’s forks had 37mm tubes) and include Honda’s TRAC (Torque Reactive Anti-Dive Control) system in the left leg. TRAC increases compression damping when the caliper grips the disc and pivots forward on its upper mount, pushing a spring-loaded plunger valve, which reroutes oil through smaller orifices to slow down fork compression. Orifice size, and thus the damping rate increase, can be selected by turning a screw in the left fork leg. There are four settings. If the bike hits a bump under braking, oil pressure builds up in the system and the plunger valve is momentarily pushed back off its seat, allowing the forks to respond normally.

The TRAC system operates only when the front brakes are applied, and only on the left fork leg. Right leg compression damping is half as stiff as maximum left leg damping.

Built into the right fork leg is adjustable rebound damping, with three positions selected by rotating a plastic knob on top of the fork cap. Each successive position increases rebound damping one third of the maximum. Left leg damping is constant.

The only adjustment directly affecting both fork legs is air pressure. A screw-on plastic cover on the left fork cap conceals a single air fitting which feeds both legs. Recommended pressure ranges from 0 to 5.7 psi.

Unequal damping rates in the legs, especially during braking, could cause fork twisting and binding. To avoid that problem, there’s a forged aluminum brace bolted between the legs.

The Interceptor has a 2.50 x 16 in. front wheel and a 3.00 x 1 8 in. rear wheel. The wheels are composites, the hubs and spokes a one-piece aluminum alloy casting, the rim an aluminum extrusion. The two parts are heated and pressed together with an interference fit and a bonding agent.

The Honda has a 120/90-16 Bridgestone G5 1 1 front tire and a 130/80-18 Bridgestone G510 rear tire. The two front brake discs are 10.9 in. and bolt directly to the wheel without carriers. Brake calipers have two pistons side-by-side on the outside, pushing against rectangular sintered-metal pads. The rear brake is an 1 1.6 in. disc with the same type of caliper.

All the Interceptor's body parts frame-mounted fairing, fenders, cowling, sidecovers and tailsection are ABS plastic. The steel fuel tank holds 5.8 gal. and has a unique rotating petcock switch that resembles a racebike’s quick-fill fitting. Because the lowest point of gas tank is below the carburetors, there is an electric fuel pump.

On Cycle World’s certified scales, the Honda weighed 532 lb. with half a tank of gas.

KAWASAKI GPz750

If that any would motorcycle be the could Kawasaki be said GPz. to When have created the other this compaclass, nies were producing more and more pseudo-choppers, Kawasaki came out with the first GPz in a mid-size 550 version, then monster 1 lOOcc trim and finally as a 750. All the GPz models became performance standards in their classes, and they also became sales successes.

That demonstrated that sport bikes could sell. Now every manufacturer has a sport bike. None are as red as the Kawasaki GPz. None are as extreme in riding position. Originally the 750 GPz looked fast and was surprisingly useful, with lots of power at all engine speeds and good comfort. This year things have changed. The 738cc engine has been breathed on, with hotter cams and a number of internal changes to handle increased power.

A new frame adds Kawasaki’s Uni-Trak single shock rear suspension to this well-aged engine. On the front is a thin shell of a fairing, larger than any of the other fairings on 750 sport bikes. The family resemblance to the GPzl 100 is obvious. The two bikes are almost identical. And both are big. The GPz has gained length and weight in its present configuration, no longer being the class lightweight it originally was.

The GPz750 has a 738cc air-cooled inline Four, with bolt-on cylinder block, dohc, two valves per cylinder and a plain bearing crankshaft. Bore and stroke are 66 x 54mm, c.r. is 9.5:1.

The 34mm intake and 30mm exhaust valves are set 60° apart, cam lobes opening the valves by pushing on bucket followers. Lash-adjustment shims are under the bucket, so valve lash adjustment requires removal of the camshafts and buckets.

There are no major engine design changes this year. The crankcases feature rubber front mounts to reduce vibration, and rigid rear mounts to maintain chain alignment and frame rigidity at the swing arm pivot. The transmission and primary drive ratios are unchanged, as are the individual shafts and gears. Final drive sprockets are different, 15/38 vs. 1982’s 13/33, making overall gearing slightly taller.

As always, the GPz’s engine spins the same direction as the w heels and powder travels from the crankshaft to a jackshaft via a link-plate chain. A straight-cut gear on the end of the jackshaft drives the clutch. The transmission has five speeds and final drive is a 630 0-ring chain. The conventional clutch has coil springs and is operated by a cable.

Kawasaki claims five more horsepower for the 1983 GPz750 engine, 85 bhp vs. 80 bhp at 9500 rpm. The extra power came from a series of changes including more camshaft duration and lift, countersinking the exhaust valve 0.5mm to reduce turbulence in the combustion chamber during intake; hand porting of the intake tract behind the valve seat, to improve flow; and pistons with higher domes to maintain 9.5:1 c.r. despite the combustion chamber volume increase caused by countersinking the exhaust valve.

Several other changes were made to maintain reliability and avoid crankshaft main and big-end bearing problems in the face of the horsepower increase. The 1982 GPz750’s connecting rods each had an oil jet, which shot pressurized oil onto the bottom of the piston dome, carrying away heat. The 1983 version doesn't have the oil jets and the pistons have a heat-resistant coating. Kawasaki engineers say that eliminating the jet holes increases oil pressure in the big end and main bearings. Those bearings are now made of a tin and copper alloy vs. 1982’s tin and aluminum alloy, because copper does a better job quickly conducting heat from the bearing surface to the crankcases. Oil cooling has been increased by 25 percent with a larger oil cooler.

Some Kawasakis have had problems with alternator rotors coming loose. To solve that problem the minimum diameter of the crankshaft alternator taper is now 25mm, up from 22mm. A larger 1 2mm bolt secures the rotor to the taper.

Three tubes make up the frame’s triangulated backbone, which is hidden under the gas tank. One center tube runs straight back and dow n from the top of the steering stem, and two others join the frame downtubes at the bottom of the steering stem and run back to intersect the center backbone tube above the carburetors. From that intersection, the side top tubes run down and outward to large box gussets at the swing arm pivot. The front downtubes run from the steering stem, in front of the engine, under the engine, and to the swing arm pivot box gussets. Triangulated tubes run back from the frame backbone and swing arm pivot gussets to support the seat and rear shock upper mount. Wheelbase is 58.9 in., about an inch longer than the 1982 model’s 58-in. wheelbase.

The rectangular swing arm is made of welded aluminum extrusions and rides on three bearings, one needle roller bearing on each side and a ball bearing in the right end of the pivot tube. Use of the ball bearing was developed by Kawasaki's road race team to handle side thrust loads during cornering. Levers connect the swing arm to the bottom of the rear shock, and the linkage is progressive. Eccentric axle holders are rotated to adjust the chain.

Kayaba makes the Kawasaki’s rear shock, which uses a coil spring and a recommended constant air pressure of 7.5 psi. There are four rebound damping adjustment settings, each set-

ting providing a 30 percent increase in damping force. Compression damping isn't adjustable. The shock damping adjustment lever is positioned on the^hock body and can be reached by removing the right side panel, which is secured by two screws. The shock air fitting is also located under the right side panel.

The top triple clamp is forged aluminum, the bottom clamp is steel, and the steering stem has tapered roller bearings. Rake is 28°, trail 4.6 in. The center-axle Kayaba forks have 37mm stanchion tubes (the 1982 GPz750’s forks had 36mm tubes) and include anti-dive fittings on both legs. Kawasaki’s anti-dive increases compression damping when pressure in the brake system closes a plunger valve. The valve reroutes oil through smaller orifices to slow fork compression. The damping rate increase can be adjusted by turning a knob on the bottom of each antidive fitting. There are four settings.

The anti-dive plunger valve is spring-loaded and blows back oil its seat when oil pressure within the forks rises past a certain point, as when the front wheel hits a big bump. When the valve blows back, the forks can respond quickly and keep the front wheel on the ground.

Fork rebound and compression damping are not adjustable. The forks are designed to use air pressure, and there’s an O-ring sealed fitting mounted on each fork tube just above the lower triple clamp. The two fittings are linked by a rubber hose and pressure can be added to both legs through a single valve stem on the right fitting. Kawasaki recommends that pressure be kept at 7.1 psi.

The GPz’s cast aluminum alloy wheels have a new spoke design and measure 2.15 x 18 in. (front) and 3.00 x 18 in. (rear). The two front brake discs bolt directly to the wheel without any carriers and measure 10.6 in. Each caliper has a single piston pushing a rectangular sintered metal pad. The rear disc also bolts directly to the wheel and measures 10.1 in. with a singlepiston caliper.

The GPz750’s plastic front fender incorporates a stamped steel fork brace. The frame-mount fairing, side-panels, tail section and rear fender are also plastic. A conventional vacuumoperated petcock has on, reserve and prime positions.

The Kawasaki weighed 515 lb. on our scales.

SUZUKI G5750E

This has, is in a some third ways, generation come full Suzuki circle. four-stroke Suzuki’s first 750 GS750 and it was a marvel of light weight and excellent handling. The performance standard in the 750 class jumped when the original GS750 was introduced.

Then came the improvements and the Suzuki got bigger and faster, but mostly bigger. Now there’s a new GS750, lighter than ever, but keeping the improvements of the last Suzuki.

In some ways, this is the least sporting of the three bikes tested. It has the smallest fairing, the most upright riding position and the least flashy styling. It is also likely to be Suzuki’s fastest 750. Picking the most sporting Suzuki isn't easy. There’s the GS750S Katana, with sharkish Katana styling, but it has the old engine and it’s heavy. The new lightweight engine is only used in the 750E and the 750ES, which has a slightly larger frame-mounted fairing than the E.

Both of the newest Suzuki 750s (E and ES) are significantly lighter and have all-new frames with single rear shocks and designed to use a 16 in. front tire.

The 1983 GS750 has a 747cc air-cooled Four with bolt-on cylinder block, dohc, four valves per cylinder and a plain-bearing crankshaft. Bore and stroke are 67 x 53mm, c.r. 9.6:1.

Intake valves measure 25mm, exhaust valves 21mm, and valve included angle is 40°. The valves are opened by forked rocker arms, one cam lobe operating two valves, with conventional screw tappets.

The engine and frame have no hold-over parts. Using lessons learned in world championship endurance and Formula One road racing, everything possible has been done to reduce size and weight. The crankcase, cylinder head and valve cover castings are good examples, following the lines of internal parts. The crankshaft has smaller counterweights and weighs 2.2 lb. less, and although primary drive is still helical gear from the crank to the clutch, a new primary reduction ratio works with smaller diameter gears in the five-speed, two-shaft transmission. Sprocket sizes for the final drive chain have been changed for the same reasons, and the O-ring chain itself is smaller, 530 instead of 630. The clutch still has coil springs and is still operated by a cable, but now has a push-rod linkage instead of a heavier rack-and-pinion linkage.

Suzuki’s new engine is rated at 86 bhp at 9500 rpm and 49.2 lb.-ft. of torque at 8500 rpm, compared to the 1982 GS750’s 8 1 bhp at 9000 and 49.1 lb.-ft. of torque at 8500 rpm. There’s no magic in that horsepower increase. Suzuki's engineers found the power by increasing valve sizes (intakes went from 23mm to 25mm, exhausts from 20 to 21mm), increasing camshaft duration, increasing c.r. from 9.5 to 9.6:1, and by redesigning the airbox and exhaust system.

More remarkable than the power increase is the weight reduction. The new engine weights 37 lb. less than the 1982 engine. Bore and stroke are the same, but the new engine has connecting rods that are 10mm shorter, with a corresponding 7mm reduction in cylinder height and 3mm shorter crankcases. The rocker arms are lighter, too, and besides the weight saved in the already-mentioned changes to the crankshaft, connecting rods, cylinder head, engine covers and transmission, special efforts were made to not over-build the crankcases. Thinner walls in non-critical areas shaved close to 6 lb. off the cases alone.

The carburetors are lighter, because they’ve got thinner casting wall thicknesses, and because different castings are used (vs. one interchangeable casting for all four carbs), eliminating extra bosses and fittings. The exhaust system is shorter and 11 lb. lighter, and the headpipes are smaller in diameter. Parts that gained weight are few and far between the oil pump rotor is 6mm thicker because the new primary ratio spins the clutch, which drives the oil pump, slower. There’s an aluminum oil cooler, and the crankshaft main and rod bearings are made of Keimet, a copper alloy containing lead, tin and nickel.

The Suzuki’s chassis is as new as its engine. There’s one rear shock, and the frame uses a combination of round and square steel tubing, painted black. Tubes hidden from view when the fuel tank and seat are in place are round; normally visible tubes are square in cross section. The backbone consists of three round tubes, a center tube running back and downward from the heavily-gusseted steering stem, two others running from the frame downtubes and curving upward to meet the center backbone tube. The two side backbone tubes then run parallel with the center tube (which terminates just above the airbox) and continue rearward to form the seat and tailsection support rails. The engine cradle is formed by the square-section downtubes, which run from the steering stem, underneath the engine, around the box-section swing arm pivot gussets, and up to meet the backbone tubes. A straight piece of square tubing runs up at an angle from the swing arm pivot to support the tailsection and seat rails on each side. Wheelbase is 58.9 in., almost 1.5 in. shorter than the old model’s 60.25 in. wheelbase.

The swing arm is rectangular aluminum, welded-together

from extrusions, with two needle roller pivot bearings. The bottom of the rear shock is connected to the bottom of the swing arm, and a lever linkage joins the top of the shock, the top of the swing arm, and the frame at a point below the seat. Suspension action is progressive.

The Suzuki’s rear shock is made by Kayaba and uses a coil spring without air pressure. Rebound damping is adjustable by rotating a remote control knob positioned on the left side of the frame, under the seat. There are four positions, the fourth position producing 88 percent more damping than the first. Compression damping is fixed. Spring preload can also be adjusted remotely, via a hydraulic system with a knob next to the damping control knob.

The upper triple clamp is forged aluminum, the lower clamp steel, and the steering stem uses tapered roller bearings. Rake is 27.8°, trail 4.1 in. The Kayaba forks have anti-dive fittings on both sliders and have 37mm stanchion tubes. Pressure from the front brake system activates the anti-dive by pushing a plunger valve in each fitting. When the plunger valve closes, it re-routes oil in the forks to increase compression damping. The rate of compression damping increase is not adjustable, but the plunger valve is spring-loaded to allow the forks to react quickly to bumps encountered under braking.

Fork rebound damping is constant. The forks use air pressure, from 2.8 to 5.7 psi, added through linked fittings mounted just below the upper triple clamp via a single valve stem on the left fitting.

The Suzuki has cast aluminum wheels, a 2.15 x 16 in. front and a 2.50 x 17 rear, and comes with a Bridgestone 100/90-16 L303 front tire and a Bridgestone 120/90-17 G514 rear tire. All three 10.25-in. brake discs incorporate steel carriers, which bolt to the wheel hubs. Calipers have single pistons pushing against round sintered-metal pads.

There’s a stamped steel fork brace built into the GS750’s plastic front fender. Plastic is used for the bar-mount fairing, side panels, tail section and rear fender. The steel gas tank has a vacuum-activated petcock with on, reserve and prime positions.

The Suzuki weighed 504 lb. with half a tank of gas on our calibrated scales.

AGAINST THE CLOCK

Adragstrip numbers that produces tell a lot numbers, about a motorcycle’s maximum capabilities. And our trip to the drags with the Honda, Kawasaki and Suzuki, all three ridden on the same pavement on the same morning by the same rider, was revealing.

First bike to the line was the Honda. Its first pass stopped the clocks in 1 1.81 sec. with a terminal speed of 114.79 mph. The Honda’s second run was even better, 11.67 sec. at 115.23 mph, and three more tries couldn’t improve that.

Next was the Kawasaki. Its first pass was 12.23 sec. at 109.35 mph. The Kawasaki’s second shot was its best, 12.13 sec. at 109.48 mph, and three more tries couldn’t get the Kawasaki out of the 12sec., 109-mph bracket.

The Suzuki broke into the 11-sec. bracket on its first pass, 11.93 sec. at 112.64 mph, and four tries later the GS750 turned its best time, 1 1.83 sec. at

1 1 2.35 mph.

So much for Round One. The Honda was the quickest and fastest, followed by the Suzuki with the Kawasaki trailing.

Round Two dealt with speed reached in a half mile, measured by our radar gun, from a 40-mph rolling start. The Honda won here, too, reaching 132 mph. The Kawasaki recorded 125 mph, the Suzuki 1 28 mph.

The drag strip times may seem confusing at first glance, what with the claimed peak horsepower being 86 bhp at 10,000 rpm for the Honda, 85 at 9500 for the Kawasaki and 86 at 9500 for the Suzuki. Elapsed times, trap speeds and rollingstart top speeds meanwhile are much more varied.

The factories aren't playing games here, nor do the dyno figures lie. Instead, there's more to actual performance than shows in the claimed figures.

Despite being the heaviest the Honda had the best times in all classes, so it clearly makes the most real-world, rearwheel power. And, because it has the widest powerband, it’s the easiest to launch off the starting line and it runs the hardest the quickest.

The Kawasaki has gained five more bhp in 1983. But it makes that power at

the expense of powerband width and the 1983 model weighs more 515 vs. 506 lb. in 1982 as well. Those factors make the Kawasaki more difficult to launch and conspired to keep it in the 12-sec. bracket even though terminal and halfmile speeds were almost identical to 1982’s 109.62 and 125 mph. (In our March 1982 test, the GPz750 turned the quarter in 1 1.93 sec.).

Like the Kawasaki, the Suzuki is harder to launch than the Honda because it lacks the Honda’s low and midrange power. But the Suzuki makes enough mid-range and top-end power, and is light enough at 504 lb., to accelerate harder and reach higher terminal and half-mile speeds than the Kawasaki.

The differences between the Honda, Kawasaki and Suzuki show up again in fifth-gear acceleration times between 40 and 60 mph and between 60 and 80 mph. The Honda took 3.3 sec. to accelerate from 40 mph to 60 mph at full throttle in fifth gear, and 4.1 sec. to accelerate from 60 to 80 mph. The Kawasaki took 5.4 and 7.0 sec., the Suzuki 3.7 and 4.4 sec.

The final track tests were stops from 30 and 60 mph. The results weren't a surprise: slowing after half-mile speed runs had already convinced the rider that the Honda’s brakes were the strongest and most linear, producing the most braking power predictably with the least amount of effort at the handlebar lever. The Kawasaki’s brakes, while strong, demanded more lever pressure and gave the rider less feedback. The Suzuki’s brakes were a distant third, lacking power, feel and controllability.

SPECIFICATIONS

Honda

VF750F

$3498

Kawasaki

GPz750

$3449

Suzuki

GS750

$3348

Three stops were made from each speed on each bike, with a dye gun wired into the brake light circuit marking the pavement the instant the brakes were applied. The Honda’s best stop from 30 mph took 31 ft., compared to the Kawasaki’s 29 ft. and the Suzuki's 36 ft. The Honda’s best stop from 60 mph took 125 ft., compared with the Kawasaki’s 1 28 ft. and the Suzuki’s 134 ft. The Suzuki was the hardest to control because its rear brake locked easily. The other bikes didn’t have that problem.

Finished with the clocks, the trio rode across deserted desert highways to an old airport-turned-racetrack. Running near flat out the 750s gulped gasoline, 27 mpg for the Honda and Suzuki, 30 mpg for the Kawasaki. That’s way off the 44, 52 and 50 mpg recorded by the Honda, Kawasaki and Suzuki on the normal 100 mi. mileage loop.

Top speeds on the open road were much different from the top speeds recorded at the dragstrip. In half-mile measured runs at the dragstrip, the Honda’s lower gearing and great midrange punch gave it the highest top speed and the Kawasaki, with its higher gearing, had the lowest speed. Held wide open for miles with riders tucked on the tanks as tightly as possible, the Kawasaki can almost match the Honda in top speed, the Suzuki falling just slightly behind as its rider fights to hold on, unprotected by a real fairing.

On the track the next morning the three bikes had no surprises. The power that made the Honda so fast in every other test, also made it the easiest to ride on the track. Because the Honda brakes require less lever effort for the same stopping power, it is easier to ride the Honda for long stretches on the track. Knowing where the track led made it easier to set the Kawasaki up for corners, where it would gracefully sweep through. The Suzuki was hard to hold on line on fast corners, wanting to be flicked around and keep changing direction. (It also had a worn rear tire by this time, which interfered with handling transitions.)

ON THE EDGE

Numbers handling with aren’t which easy to to find define and those that can be discovered may not mean much. The SAE has a standard for measuring lean angle, for instance, which spells out how a factory should report cornering clearance. It’s a good idea but when you’re dealing with different suspension settings, tire sizes, etc., it doesn’t correlate to the real world.

Even so, the three bikes here have exceptional lean angles. Ridden around corners at speeds that would have had last year’s best sports bikes grinding pegs, these three have cornering clearance to spare. The Honda, in particular, has the narrowest engine and the widest tires and all its parts are carefully fitted close in and high. Scraping anything on the Honda requires either reducing suspension preload or riding at race-track speeds. The Suzuki has the least cornering clearance, dragging the sidestand bracket at speeds when the other bikes aren’t even touching footpegs.

Two of these bikes have 16-in. front tires. One doesn’t. That, combined with other chassis differences, helps explain handling differences, but tire size alone doesn’t account for all the difference. In this instance, the bikes with the smaller diameter front tires have the quickest steering. Good. That fits the theory. Smaller tires and wheels create less of a gyroscopic effect, making it easier to turn the bars and steer the bike.

It helps that all three have the same wheelbase, identical rake (within 0.2°) and the same width handlebars. That makes comparisons easier. All three don’t have the same trail. Here, the Honda is the shortest at 3.9 in., the Suzuki slightly longer at 4.1 and the Kawasaki the longest at 4.6. Longer trail makes it harder to turn the wheel, everything else being equal, fitting in with observed handling. Tire sizes and profiles also come into play.

The Honda and Suzuki are both very quick-steering motorcycles, requiring little effort to turn, and the Suzuki, with a smaller front tire, easily leans over to use every bit of available tread. The Honda’s wider front tire has a bigger contact patch and a flatter profile, making the steering slightly less quick entering a turn but making the bike more stable after it’s in the turn. The Kawasaki, with a larger diameter (and wide) front tire and long trail is the heaviest steering, on paper and on the road.

The differences were easy to spot with all three bikes on a long, serpentine country highway, winding down from a ridge to the valley floor below. Going downhill, power was less critical, and steering and brakes became more important. On the first trip down, the Suzuki took off, followed by the Kawasaki, with the Honda rider a little ways back, observing. For the Suzuki rider it was an enjoyable 10 mi. ride, flicking the bike back and forth, diving into corners late and making small corrections with the light and responsive steering. He needed to use more braking effort than the other riders and had to concentrate more on braking, but found the ability to make quick direction changes to be highly valuable on this road.

The Kawasaki pilot, meanwhile, was building up a sweat wrestling the heavysteering GPz back and forth. On this unfamiliar road he couldn't pick perfect lines going into corners and had to fight the bike to make the necessary lastminute corrections. His brakes required less effort, but even on short straights he couldn’t make up any time with power.

Back on the Honda, there was another happy rider, calmly cruising down the mountain with ease, not using all the brakes or power or steering and able to watch the Suzuki use all its available cornering clearance and the Kawasaki use all its ability to turn.

At the bottom of the hill riders switched bikes and headed back up, now' more dependent on power. On the initial short straight the Honda blasted past the Kawasaki and Suzuki and headed toward the first turn. The Kawasaki rider downshifted again. The Suzuki dove deeper into the first turn. Starting up the mountain the Honda opened a large lead wfith its exceptional power, outstanding handling and overpowering brakes. This run became a training ground for the other riders. On the Honda no adaptation was necessary. Everything worked smoothly, with no special effort or concentration required. Not having the midrange punch of the Honda, the Suzuki rider had to make sure he kept the engine in the powerband. Still, he lost ground coming out of every corner. The Kawasaki rider had to cope with two shortcomings. His bike had the narrowest powerband, needing the slick-shifting gearbox rowed like an oar. His bike also had handling that required a premeditated riding style. In order to get through a corner quickly, the Kawasaki had to be aimed carefully before the corner began, so it would follow the correct trajectory through the corner and out the other side. Done right, the Kawasaki could corner as quickly as the other bikes. It just took more graceful lines.

Before the next round the Kawasaki and Suzuki riders turned rear suspension damping up to the maximum to eliminate some wallowing detected in the rear suspensions. This made the bikes feel more stable through the corners, but didn’t change cornering speeds or power.

WHAT THEY'RE LIKE AT HOME

Timed cycles runs are aside,these more different three than motorany numbers can show. Three sporting 750s,all sensationally quick,all startlingly attractive. Yet the sensations they deliver to the rider, and their responses to the rider, are all distinct.

Think of size. The Honda is the heaviest, and it feels large. The tank and seat are wide. The handlebars are a medium stretch forward. The sensations provided by this bike suggest it could be a lOOOcc motorcycle. Much of this is the lowspeed engine response and power, some of it is the irregular exhaust beat that masks engine speed. But the bike feels big. The Suzuki feels smallest. It could be a 650, or even a big 550. It has the quickest steering, requiring the least effort. If you could measure the steering torque necessary to change direction from full left to full right in a given time, the Suzuki would require about one-fifth less steering effort than the Honda, and half the steering effort needed by the Kawasaki. In addition to the easy steering, the Suzuki has the least sporting seating position. Suzuki’s handlebars are the highest, and pull back the farthest. The Suzuki’s footpegs are the farthest forward. You sit more upright, where it’s easy to control the bike at low speeds. Not having to stretch as far to hold the handlebars, you assume the Suzuki is shorter. But it’s not. Then there’s the Kawasaki. It was the first to arrive, and everyone climbed off it marveling at what a nice motorcycle it was. Smooth. Powerful. Easy shifting. But compared with the other sporting 750s, the GPz has a distinctly truckish feel. It is the longest reach to the low-set handlebars, and the pegs are tucked up closest to the rider’s bottom. Steering effort is noticeably heavy. Even with the best vibration isolation, the GPz retains that Kawasaki mechanical feel.

Comfort on these bikes is determined more by seating position and use than by seat padding or suspension compliance. All the suspensions do an outstanding job of keeping road irregularities away from the rider. Because the Suzuki has the most upright seating position, it’s the easiest and most comfortable to ride at low speeds, on up to freeway speeds. Above freeway speeds that upright riding position props the rider in the wind like a sail, where he has to hold on tightly, bend his arms in an acute angle and try to duck out of the wind. The Honda has a lower seating position that works well around town and on the freeway and is acceptable at very high speeds. It has more fairing area than the Suzuki and keeps more wind off the rider. The Kawasaki can be work to ride around town. Leaning forward, the rider is in push-up position, straining arm muscles to hold upper body weight.

When speeds go above freeway levels, way above in particular, the Kawasaki is at home. It has the biggest fairing, blocking wind for the rider, With the low seating position, it’s easy to duck behind that fairing making prolonged top speed runs easy and comfortable. After 100 mi. of nearly flat-out riding on empty desert highways the Suzuki rider began slowing down, tired from the effort. The Honda rider was squirming a little, and the Kawasaki rider was still exploring redline in top gear.

Vibration can be a hidden fatigue factor in long rides. The Kawasaki wins the vibration control battle with its semirubber mounted engine transmitting the least vibration to the rider at all engine speeds. The Suzuki has a two-stage vibration level. At low speeds vibration is well controlled, feeling damped. Over 4000 rpm, vibration picks up slightly. As soon as the engine reaches 5000 rpm everything hits a magic stillness that’s wonderfully comfortable. A few hundred rpm above that there’s a resonance coming from the gas tank, but this only between 75 and 80 mph. Above 80 vibration drops off again.

All these motorcycles have adjustments, but not all the adjustments are equally effective or easy to use. The Honda and Kawasaki have adjustments for front brake anti-dive, the Suzuki doesn't. The Suzuki also has the least effective anti-dive. The others were set at maximum during most of the test, without problem. All the bikes have a single air filler cap for the forks. Changing air pressure has the most effect on ride height and little effect on ride comfort. The Honda also has a convenient damping adjustment at the top of the right fork leg, but at the softest setting it didn't wallow or wiggle, and at the firmest setting it wasn't uncomfortable.

Rear suspension adjustments are not so easy on some of the bikes. The Suzuki is best here, with damping and spring preload easily set without tools or air pressure, and without removing any covers. The Honda has the air valve under the left sidecover and the damping adjustment under the seat. This is not convenient.The Kawasaki is the least convenient, requiring the right sidecover to be unscrewed before filling with air or moving the mysterious push-pull damping control. There are four numbers, but nothing that lines up with the numbers. Not knowing which direction was soft and which firm, we experimented and found that one extreme allows some rear suspension wallowing under high speed cornering, and the other extreme eliminated this. Between these settings the differences were too small to be noticed.

No adjustments are provided by the multi-piece handlebars. The handlebars also can’t be replaced by ordinary tubular bars, so the position of handlebars is more critical on these bikes than on others.

Hard-edged sport bikes were once thought to require suffering and inconvenience from their riders. These bikes can lay that myth to rest. While offering performance, collectively, that no stock Ducati or Laverda can match, they also serve as wonderfully convenient transportation.

Keys fit into locks on the steering head, all containing fork locks. Choke controls on the Honda and Suzuki are on the left handgrip, where they’re easy to use. The Kawasaki still has a button on the carburetors for choke control, and it requires the most use of choke. Clutch pull on all the bikes is easy, though the Honda’s hydraulic clutch control isolates the rider more from the clutch, making it more difficult to feel when the clutch is engaging.

All the bikes have bright quartz-halogen headlights. The Kawasaki’s fairing doesn’t fit tightly around the headlight, though, and there is an annoying reflection inside the fairing at night.

The Honda’s mirrors, mounted on the bars with L-shaped stalks, gave the rider the best view. The Kawasaki’s mirrors, mounted on the fairing, were not as good, and folded flat against the fairing at any speed over 80 mph. The Suzuki’s mirrors showed more of the rider’s elbows than of the road behind the bike.

Instrumentation is a good clue to the character of these bikes. The Honda has a clean metal panel in the fairing, containing a 13,000 rpm tach, 150 mph speedometer and the usual warning lights. At one side is a coolant temperature gauge, the other side has a fuel gauge. The look is businesslike, direct and clean. The instruments are easy to read.

Suzuki has clumped similar instruments in a tidy little shell of a fairing. A 12,000 rpm tach, 140 mph speedometer, fuel gauge and oil temperature gauge are mounted around a digital gear indicator and above the usual warning lights. Everything fits well. It looks compact, stylish, restrained and everything is easy to read.

The Kawasaki has two clusters of instruments. Up on the steering head there’s a large speedometer (limited to 85 mph on earlier examples but scheduled to be replaced by 150-mph speedometers) and a tachometer-voltmeter. Also in the bar-mount panel are lights for turn signals, neutral and all-purpose warning.

This last tells the rider to look down at the second panel, a small pod atop the fuel tank. This cluster holds the fuel gauge and lights for oil pressure, battery fluid and sidestand deployment.

It’s well out of the rider’s field of view during most riding, which is why the look-down warning light on the bars. This may be fine when waiting for long stoplights or slow trains, but it’s the worst instrumentation of the three.

Maintenance tasks are simplified by the electronic ignition on all three bikes. But valve adjusts could be easier. The Honda and Suzuki have screw-adjust tappets, but the Honda’s top radiator must be removed to get the valve cover off. And on the Kawasaki the cams have to be removed to replace adjusting shims, though this system may hold its adjustment longer. The Honda has a simple spin-on oil filter, but the lower radiator and cowling have to be removed to reach it. Removing the rear wheel is much easier on a couple of these bikes. The Honda wheel can be pulled in about two minutes, and the Suzuki no longer has to have the exhaust system removed to pull the rear axle.

The Honda’s hydraulically-operated clutch is self-adjusting while giving away feel. And when it’s cold the clutch drags and makes shifting difficult. Warm, it grabs and the shifting is notchy though positive, all of which combine to make the Honda the worst in this category.

The Kawasaki and Suzuki clutches use cable actuation, with good feel and the need for occasional adjustment. The Kawasaki gearbox worked fine, better than we’ve seen from that factory recently. The Suzuki’s clutch was normal and the shifting almost miraculous, incredibly light and smooth and positive. It’s the best we can remember.

All three bikes came with good tires, able to stick on a variety of surfaces under hard use. They were ridden in the rain, no problems. But with 1500 miles on them, the rear tires on the Honda and Kawasaki were nearly gone and the Suzuki’s was down to the wear bars.

Prices are close, $3498 for the Honda, $3449 for the Kawasaki and $3348 for the Suzuki, all before discounting.

THE JURY RETURNS

What some we imagination need to do here and is make use some impossible demands.

The subjects of this investigation are three sporting 750s. If any of the trio is a bit too sporting, why, each of the factories stands ready to deliver the same basic package with a wider powerband, higher bars, etc. Nor have we even mentioned the other 750s, which range from the touring-ready Yamaha Seca to the evergreen Triumph Bonneville (now with eight valves and less vibration, watch this space). Further, it’s difficult to find any new bike that doesn’t rate at least a nine on the ten-point scale.

And yet, we need to pass judgement: The Kawasaki GPz750 was the first delivered and we thought it was the finest sports 750 we’d ever seen. It’s deliberately extreme, in that the designers leaned on the engine to keep it in the power sweepstakes and the GPz’s peak performance comes at the expense of punch at mid-range. Good brakes, good suspension and the fairing and riding position make it comfortable at unprintable speeds. The GPz’s suspension geometry and front tire make it feel long, strong, stable and not quite the precision instrument its rivals are. Judged alone the GPz is a terrific motorcycle. Its performance pales, so to speak, only by comparison.

The Suzuki GS750E is an impressively different approach to the same set of rules. If the Kawasaki uses a revised version of an old engine and the Honda a new version of a new engine, then Suzuki has a revised version of a new engine. And it works. Good power, less weight. The Suzuki is the lightest and smallest and feels even lighter than it is. The Suzuki is quickest through a snap roll. High (relatively) bars and no fairing make it the most taxing at top speed, but it’s also the most relaxing in town. The rider who can live with the second-quickest 750 in production, who doesn’t get to spend most of his time defying the National Speed Limit, might well find the GS750E the most satisfying of the trio.

And last, for the first time in this narrative, we have the Interceptor. The biggest, the heaviest, the most powerful, the quickest, the fastest. The Honda has a combination of strengths which the rider can put to his advantage, along with an agility that makes it the most forgiving of the three and yes, we all like to pretend looks don’t matter but they do and the Honda dazzles the eye.

The Interceptor wins. Q