Suzuki Gsx-R600

SUZUKI GSX-R600

CYCLE WORLD TEST

THE WAIT IS OVER

GOOD BUSINESS SENSE DICTATES that you don’t change a product that’s selling, no matter if you’re talking motorcycles or mousetraps. This philosophy explains

why Suzuki has stuck with its best-selling, air-and-oil-cooled 600cc Katana for so long despite the lamentations of enthusiasts desiring a more sporting middleweight.

Well, all that has changed. Meet Suzuki’s better mousetrap, the new liquid-cooled GSX-R600.

Suzuki’s first-ever 600cc repli-racer is part of the same family as the nonU.S. liquid-cooled GSX-R750W (see “Suzuki Starts Over,” CW, January, 1992). In fact, it is essentially identical to the redesigned 750, save for its different bore-and-stroke figures, and smaller valves and carburetors.

Aside from the switch to liquid cooling, the primary goal of new-style GSX-R engines was to provide a low center of gravity and a more forward weight bias. The easiest way to achieve this is to place the motor low in the bike’s frame, but the side-effect is usually reduced ground clearance.

Suzuki got around this pitfall by designing an extremely narrow motor. Most of the reduction in width came through relocating the starter clutch from its traditional position on the left end of the crankshaft to a location atop the crankcases. But Suzuki didn’t stop there: The crankshaft and transmission shafts were shortened; the number of driven clutch plates was reduced from nine to seven; and the distance between cylinder centers was reduced. The result is an engine that is nearly 3 inches narrower than that of the 600cc Katana, and more than an inch narrower than that of the 400cc Bandit.

Shortening the transmission shafts necessitated a reduction in gear widths, but gear strength was retained by increasing the outside diameter of each gear. Additionally, a multi-splined redesign of the transmission shafts results in more surface area and greater load-bearing capacity for smoother shifting.

Also new is the method of valve actuation-the third seen on GSX-Rs in as many years. The new system is of shim-under-bucket configuration, wherein the cam lobes act directly on the valves without rocker arms. It provides more accurate valve control at high rpm, and also increases valve adjustment intervals from 3500 to 7500 miles-the traditional 600-mile initial service is no longer required.

Other changes to the valve train include the use of one, rather than two, springs per valve to save weight; and a reduction in the number of camshaft journals per cam from five to four in the interest of minimizing friction and mechanical loss. Cam timing has been juggled so that the intake valves now open and close later than on the Katana, with longer duration. The exhaust valves open earlier and close later. Exhaust-valve lift was also increased by 1mm. (California models have less duration and less lift to help them meet emissions standards.) Included valve angle of the new GSXR is just 32 degrees, down from the Katana motor’s 40 degrees. Practically the entire piston crown is machined for valve clearance, resulting in an extremely compact combustion chamber with a sky-high 11.8:1 compression ratio. Another new feature is the liquidcooled oil filter, which, like those seen on some other brands of motorcycles, consists of a collar beneath the oil filter through which coolant circulates. Finally, a huge, curved radiator and an electric fan replace the old bike’s oil cooler.

As on the Bandit, the new GSXR600 motor features an externally mounted waterpump that dovetails to the oil pump. The oil pump has also been changed, largely due to the fact that oil is now used only to lubricate the motor, not to cool it as before-though cooling oil is still sprayed on the pistons’ undersides, as with the old-style GSX-Rs. Thus, a single-stage oil pump replaces the dual-stage unit employed previously.

The net result of these cooling-system changes is a motor with more than twice the cooling capacity of the oilcooled motor. This should prove especially helpful in racing, where excessive heat has long been a thorn in the side of modified GSX-Rs.

To improve cornering clearance, Suzuki’s engineers devised a few clever

ways to more closely tuck the 4-into-2-into-1 exhaust system under the motorcycle. Firstly, the motor’s oil pan is offset to the left, providing room for the steel collector on the right. Secondly, the swingarm is curved on the right side, and the rear brakestay arm was eliminated, to provide clearance for the stainless-steel muffler; the rear-brake caliper mount now slots into a boss on the swingarm. Lastly, as on previous GSX-Rs, the muffler canister is beveled at its leading edge, providing an added measure of cornering clearance.

Suspension, brakes, wheels and tires are all from the GSX-R catalog. Up front, there’s a fully adjustable, inverted, cartridge-style, 41mm Showa fork, while an equally adjustable Showa shock with remote reservoir resides at the rear. The only obvious difference between

these components and those of recent GSX-Rs is that the fork’s compressionand rebound-damping screws, and the shock’s compression-damping screw, no longer “click” when you turn them. They’re now infinitely adjustable, and a punch mark on each of the screws and its corresponding housing provide reference points.

As for the shock’s rebound damping, it is adjusted by a four-position knob located at the shock’s bottom. Shockspring preload is adjusted with a threaded collar-though no spanner is included in the bike’s toolkit-and forkspring preload is adjusted by turning the nut atop each leg with the included 22mm box-end wrench. Seven lines are scribed in the fork’s preload adjuster for ease of reference.

As on the GSX-R750 and 1100, Dunlop D202 radial tires are fitted to the 600. The 600’s front tire is designated a D202FG, however, the final letter referring to its slightly different construction, intended to offer a more compliant ride. Both wheels measure 17 inches in diameter, the front being 3.5 inches wide and the rear 5.5 inches-the widest in the class. Nissin brakes are used at both ends, a pair of four-piston calipers grasping 12.4-inch discs at front, and a single twin-piston caliper grasping a 9.6-inch disc at rear.

Swinging a leg over the GSX-R600, the first thing the rider notices is the long reach to the clip-on handlebars. Though not of Yamaha FZR1000 distance, they are a long way from the seat. Not so far from the seat are the rearset footpegs, which are too high for anything except racetrack or hardcore sporting use. Freeway rides of any duration are an exercise in sadomasochism. If anything, the GSXR600’s seating position is more painful than that of the GSX-R750, which, if you’ve ever ridden one, is hard to fathom. At least the seat is cushy, especially considering its racer-like appearance.

Much of the GSX-R’s uncompromising nature is forgiven once you’re in the twisties, however, because there, this motorcycle shines. Its motor is one of the most vibration-free we’ve ever sampled, and its transmission shifts almost too smoothly: Neutral engages as easily as any other gear, so it takes a deliberate pull on the lever to bypass neutral and catch second. The remainder of the six, close-ratio gears engage with only the slightest snick of the lever, even while making clutchless racetrack upshifts.

The GSX-R’s engine revs slowly up to about 7000 rpm, at which point it begins to build power and rev more quickly. Below that point, it feels soft, much like the Bandit 400; above that, it builds power linearly and continues to pull strongly past its 13,500-rpm redline all the way to its 14,500-rpm revlimiter cutoff point. Performance testing showed that we’d been fooled in more ways than one. Because while the GSX-R felt fast, it clocked a dismal 11.95-second/1 15.7-mph run through the Carlsbad Raceway quarter-mile. That’s seven-tenths of a second and nearly 7 mph slower than the class-leading CBR600F2 we tested last year. Part of the problem is the GSX-R’s tall first gear, which requires plenty of clutch slippage for hard launches.

While the engine and transmission work smoothly, and carburetion is excellent, a slight amount of driveline lash just off of closed throttle mars an otherwise perfect ride.

So, overall, the motor feels excellent. How’s the chassis? Believe it or not, even better. Tires, brakes and suspension are all first-class, maybe even the best of the middleweight sportbikes. The GSX-R has a taut feel, yet its ride is superbly compliant. It steers more lightly than anything this side of a 250cc racebike, flicks into comers and changes direction effortlessly, and steadfastly holds its line in a turn, with not a hint of twitchiness. Cornering clearance is excellent; on the racetrack, we barely scuffed the fairing’s trailing edges, the muffler’s protective plate and the kickstand.

But despite the GSX-R’s light handling, it’s no featherweight. In fact, when we weighed the GSX-R, we thought for a second that our scales were broken. At a porky 486 pounds dry, the GSX-R weighs 57 pounds more than the Honda CBR600F2, and 20 pounds more than the Katana 600.

The GSX-R’s lack of midrange power let it down in top-gear roll-ons, where it took 6 seconds to accelerate from 40-60 mph. By contrast, last year’s torquey Yamaha FZR600 took

just 3.9 seconds. But if the Suzuki is slow in acceleration, at least its top speed is in the ballpark. At 142 mph, it’s just 2 mph slower than the rapid Honda CBR.

In terms of price, though, the Suzuki again comes out at the wrong end of the specs column. At $6199, it costs a full $500 more than the CBR-never mind that the GSX-R buyer gets free admission to a Team Suzuki Endurance Riding School, a $200 value.

It’s ironic that the performance of a bike

descended from the 1985 Suzuki GSX-R750-which ushered in a new era of lightweight sportbike performance-could be hampered by excessive weight. But times change, and it is now Honda-with its featherweight, 432-pound CBR900RR-that carries the technological torch.

So, this new GSX-R600, a half-second too slow, 50 pounds overweight and just $500 less expensive than the firm’s current air-and-oil-cooled GSXR750, has some serious flaws. But, let it be known that Suzuki has finally fired its first serious shot into the middleweight sportbike battle. The wait is over, even if the finished product is disappointingly overweight.

How will the GSX-R fare against its tough competition, notably the classleading Honda CBR600? We’ll let you know next month when Cycle World publishes an all-inclusive, seven-bike 600cc comparison. Stay tuned. □

SUZUKI GSX-R6OO

$6199