Suzuki GSX 600F

Designing an all-new motorcycle in the ultracompetitive 600 sport class is not all beer and skittles, let us assure you. The middleweights are extremely important to a motorcycle company since they are the machines that sell best. We all lust over the liter-class and 750 road rockets, but when the finance officer and the insurance agent look us square in the eye, most of us find the under-$4000 price bracket quite comfortable, thank you.

And in this day of rapidly accelerating technology, not to mention rapidly accelerating motorcycles, 600s are becoming the bikes of choice for even those riders who can afford something bigger and faster. A good-running 600 can top 140 mph and come amazingly close to equaling the quarter-mile times of a five-year-old 1100. So the power is there—and, oh my, so is the handling. The 600s have a rare combination of power, weight and responsiveness, which all adds up to something called balance.

Suzuki had the unenviable position of taking on three of the best-handling motorcycles ever sold when it set out to build the new 600 Katana. The Yamaha FZ600, though three years old, is still ranked among the finest racetrack handlers ever bolted together. It's small, a little slow and uncomfortable, but it also turns like a centrifuge. The Honda Hurricane, of course, is already a legend; its combination of awesome high-rpm punch and sure-footed, highly stable chassis has made it an all-conquering production racer, and its slick bodywork and well-done ergonomics have established it firmly atop the sales charts. And the new Kawasaki Ninja with its smooth, torquey motor, ul-traquick steering, sport-touring riding position and crisp lines challenges the Honda for practical street-bike supremacy, even if it's not quite the race bike the Honda is.

The traditional way to build a U.S.-market 600 is to start with a domestic Japanese 400 and leave it on the boring bar until it goes up a class. The new Katana is a startling departure from the usual upsizing trend; it has, for all intents and purposes, the engine from the dominating '87 GSXR750 jammed inside its little steel-tube frame. The GSXR mill is very light and small for a 750, allowing Suzuki to use it in the 600.

The entire bottom end of the new 600 comes right off the GSXR750 production line; the crank, oiling system, rear-mounted alternator setup and the basic transmission are all identical. The 600's trans has a shorter first gear to compensate for the torque lost to the missing 150cc, but everything else is the same. The differences are all upstairs; stroke is the same as the 750's, but the bore has been reduced to 62.6mm for a final displacement of 599.2cc. The revamped '88 GSXR750 uses a shorter stroke than the '88 GSX600, in fact.

The new 600 has the same SACS oil-cooling system as the GSXR, and the four-valve TSCC combustion chambers and valve gear are identical in design. Valve sizes are down to 23mm intake and 20mm exhaust; cam timing has been juggled, with less duration than the 750 but identical lift. Compression ratio is up to 11.3:1, an amazing figure for an engine without water running through it. The well-proven forked-cam-follower system, with one cam lobe opening two valves, is retained. The carbs are similar to the 750's but smaller, of course; the new Keihin CVs are 31mm across the throats.

The basics of the clutch are the same as the 750's, but the 600's is actuated by a cable, not by the hydraulic system used on big brother. The 600 uses a new microprocessor-cued ignition system for very precise timing control through the rev band. And the exhaust system is a conventional, slightly heavier four-into-two system instead of the 750's four-into-one; the added muffler volume let Suzuki's designers get a little more power without tweaking the sound meter's sensitive ears.

You are asking yourself a question. Will the 750 top end fit right onto a 600 bottom end? We think so. In any case, a complete GSXR750 engine should fit right into the hole left in the frame by the vacated 600; there might be some breathing problems with the 600's smaller seven-liter airbox, and one might be forced to punt when it came to the different exhaust system. The prospect is tantalizing, though, for both customers and Suzuki; GSXR750 power in a comfortable yet highly sportable chassis like the Katana's would be lots of fun. And if Suzuki chose to, it could blow the competition's 750s out of the street-bike market by selling 750 Katanas for almost the same price as its rival's 600s. Hmmm.

The new Katana departs from GSXR practice in its all-steel frame, with rectangular members reaching around the engine rather than above as on the GSXR. This lowers the tank and the CG and eliminates the pronounced step up from the GSXR's seat to its high-boy tank. The engine is rigidly mounted at the rear but rubber-mounted at the lower front to keep any buzziness away from the rider. This cost the designers some weight, compared to the rigid mounting of the Honda Hurricane; the Honda has no frame under the mill, but the Suzuki has a full cradle underneath which can be quickly unbolted for engine removal. Another steel cross piece lies under the tank; it serves to stiffen the widely spaced side rails and comes out with four bolts for easy access to the valve cover for adjustments.

Seventeen-inch wheels are used; the front is the same size, 2.50 inches wide, as the Hurricane's, and the rear at 3.00 inches is half an inch narrower. The suspension units are straightforward but unexpectedly robust; a new Full Floater system, without the eccentric units of the early GSXRs, keeps the back off the ground, and huge 41mm fork tubes are used at the front. There are no provisions for air or damping adjustments at the front, and only spring preload is adjustable at the rear; the cost analysts won the battle against the engineers in this department.

When spring and damping rates were selected, the emphasis was placed on ride and comfort rather than racetrack-sharp response. Even so, the 600's suspenders work quite well on a closed circuit, especially for riders of average weight or less. Suzuki decided to give the majority of riders what they needed with the suspension most of the time and leave the racetrack settings to the racers. Production racers toss the stock shock and redo the fork anyway, reasoned the engineers, so why not cater to the bike's real-world audience instead of the lunatic fringe?

The brakes are familiar to any GSXR fan; they are the same four-piston double-action calipers, squeezing 290mm floating discs at the front (10mm smaller than the GSXR750's), with a single 250mm plate at the rear. The front discs are 14mm larger in diameter than a Huricane's; they worked acceptably on the street, with slightly mushy feel and moderate lever pressure, but could be made to fade seriously out at Riverside Raceway, allowing the lever to come in nearly to the handlebar. We suspect a bleeding problem is the culprit; Suzuki knows how to make brakes that don't fade, and we are confident that a little less air in the lines and perhaps a change to organic brake pads would have the binders ready for the racetrack.

As advertised, the 600 is a first-class street bike. The engine is slightly coldblooded on crisp mornings, prone to either stalling or wild revving depending on the carb-mounted choke setting, but after a mile or two it runs cleanly.

The redone engine has an entirely different character than the race-ready GSXR, even though there are few obvious differences. The Katana version feels much smoother, though a little less responsive to throttle control; it has less power and nearly the same flywheel effect as the GSXR motor. Power starts at the bottom and builds progressively all the way to its 9600-rpm torque peak; it doesn't have the rush of the Hurricane, but it has more usable power in the low-end and midrange and keeps on building until it flattens out slightly between 10,000 and its 12,000-rpm redline. Drive-line lash is well controlled, and the six-speed gearbox is slick and silky, with a quick dab of the toe sufficient to make a change. Vibration is present but well-controlled; a slight buzz sets in at 4500 rpm and stays in the bars and tank until the tach needle sweeps past 8000. Still, the new 600 has a sweetheart of an engine package, smoother than the Hurricane's or the FZ's and with a well-thought-out spread of power for most riding situations from commuting to racetrack craziness. It is fast; see the accompanying sidebar for test figures.

The riding position is an excellent compromise between sport crouch and touring plush; the pegs are low enough to allow the rider to get his legs underneath him for support, and the handlebars are high and wide enough for good leverage and a relaxed riding position, without the wrist crunch experienced by GSXR and FZ owners. The seat is deeply dished for the rider but is commend-ably flat and with sufficient padding for long hauls; the 5.3-gallon tank gives out before most rider's buns. The Hurricanelike fairing directs air out and around the rider quite well for such a small machine; the windshield provides a small pocket of still air for a crouched rider and breaks up the impact of the windblast for an upright pilot.

The Katana is set up with quite radical steering geometry; rake is a steep 24 degrees 40 minutes, reminiscent of GP machines. This is a degree and a half steeper than a Hurricane, with its similar-sized wheels; trail is 3.9 inches for the Suzuki, 4.1 for the slower-steering Honda. To get back some stability Suzuki's designers went with a longer wheelbase; the Katana is 56.3 inches from axle to axle, the Honda 55.5 inches.

In the real world this translates to medium-quick, responsive steering, though not nearly as twitchy as Kawasaki's darting 600 Ninja. The relatively soft suspension takes away some precision, especially at racetrack speeds, but the Katana is still easy to place where the rider intends, and line changes are made without much muscular effort. The extra .8 inch of wheelbase the Suzuki has compared to the Honda seems to be placed between the front wheel and the CG; the front end feels quite a bit more vague than the Honda's firmly planted front, but even bumpy full-bore sweepers failed to dislodge the Suzuki's steering end significantly. Slight bar pressure is required to keep the 600 leaned into a corner with the throttle on; this gives the rider excellent feedback of the road and rubber interface. The new Dunlop K655 bias-belted tires work well for OEM rubber; they are not particularly precise but roll in smoothly and slide predictably, even if their traction level is a ways below the best aftermarket sport skins.

Even with its pegs mounted low enough for good rider comfort, the Ka-tana's cornering clearance is more than adequate; Big Boy Boehm dragged the left peg lightly out at Riverside and didn't touch anything more solid than his knee on the right. With the suspension up high for production racing, cornering clearance will not be a major problem, even for the Schwantzes among us. The cen-terstand doesn't drag for a very good reason: there is none. The brackets are there on the frame, though; the actual stand will be available as an option.

Suzuki's first 600cc sport bike is a very nice piece of engineering; we hope the public will be able to get past the machine's somewhat confused graphic treatment and questionably detailed bodywork to find out just how nice. The fairing works quite well and manages to keep most of the engine's heat away from the rider, but in terms of fit and finish, it is simply not in the same league as the Kawasaki or the Honda. The pieces don't seem to fit together well at the seams, and the round oil-filler access panel on the right doesn't fit the contour of the fairing surrounding it. The stripes under the tank don't meet precisely at the joint between the fairing and the side panels, and the graphic line formed by the colored seat and tank gives the machine an awkWard, frumpy look. Even the grab rail looks strange, an almost organic hoop floating above the tail section. Suzuki has an optional tailpiece that replaces the rear seat and the grab rail; we haven't seen one on the bike, but photos in the brochure indicate it will do the Katana's looks a world of good for solo-oriented riders. Suzuki's stylists have never been on the cutting edge of hipness; in our opinion, the new Katana needs help in the finish and graphics department if it's going to make a dent in the competition's sales figures.

Practical street-riding details get typically mixed reviews. The mirrors are mounted far enough out to give views of the road behind and only the outside edges of the rider's shoulders. The horn, though, is the usual Japanese joke. The engine-mounted choke is something of a pain, especially in the first tentative warm-up of the day.

Below the skin, though, Suzuki's new middleweight is a well-done package of effective compromises; it shines in ergonomics, engine performance and tracta-bility, and it handles and stops well enough to keep up with anything in its class. We don't know how well-massaged versions will do in the production-racing wars, but Suzuki is confident; the company will be offering the same generous contingency awards to 600 Katana riders as it has to GSXR riders in the past.

The Katana has turned a well-defined class, with each bike having its own strengths and weaknesses, into a free-for-all. The new kid on the block is a very strong contender, with what may be the best combination of power, comfort and handling yet offered for casual street riders—and serious enthusiasts as well. M