Yamaha Yzf600r Thunder Cat
YAMAHA YZF600R THUNDER CAT
CW RIDING IMPRESSION
THE T-CAT GETS CLOSER
WHAT DO YOU DO WHEN YOU’RE THE WORLD’S SECond-largest motorcycle manufacturer and your single most important sportbike is no longer competitive on the racetrack? If you’re Yamaha, and the class in question is 600 Supersport, you get serious.
Now is a good time to be serious about 600s. Sales in this sector currently account for 33 percent of the total sportbike market worldwide (up from 20 percent five years ago), and 600s remain the best-selling sportbike category in the U.S. by a wide margin. So there’s no room for stop-gap measures.
Yet a stop-gap measure is precisely what Yamaha dealt buyers two years ago with the first makeover of the FZR600 it introduced in 1989. Now, with the YZF600R Thunder Cat, company engineers have done the job properly. By building on the existing YZF600, Yamaha achieved Mission Impossible, transforming the liquid-cooled, 16-valve, slantblock, 600cc inline-Four into a serious contender for racetrack honors while simultaneously making it more user-friendly on the street.
Compared to its Japanese rivals, the old YZF did things a little differently. It relied upon a relatively long-stroke (62.0 x 49.6mm) engine that made power through optimal cylinder filling and combustion. (The others rely upon short-stroke motors that develop horsepower via high rpm.) Trouble is, Yamaha’s strategy never really delivered the midrange and low-end torque the package promised. It does now.
To start with, throttle response is much crisper than before, thanks to the electronic throttle-position sensor fitted to the new 36mm (2mm larger than before) Keihin CV carbs. This system compares engine rpm with throttle opening and specifies optimal ignition advance. The result is really noticeable at low rpm: The Cat will pull cleanly from 2000 rpm-but only if you don’t crack the throttle open at low revs. Do that and the bigger carbs will flood the engine and create a flat spot. Gas it hard above six grand, though, and there’s a midrange punch that wasn’t there on the old YZF. It pushes very quickly toward the claimed 11,500-rpm power peak and the engine’s 13,800-rpm appointment with its rev-limiter.
ALAN CATHCART
Yamaha claims 100 horsepower for the T-Cat, but liberally sprinkled throughout the press kit are references to 105 hp. That represents a 5 percent increase, and is almost certainly what the bike really makes. Claimed torque is a classleading 48 foot-pounds.
The newfound power was obtained by lightening various engine components, such as the pistons and the ignition rotor, and by improving the engine’s pumping abilities. The pistons are now forged rather than cast, which along with beefed-up valve springs and camshafts help make the engine stronger at high rpm. A new exhaust system incorporating a crossover pipe under the oil sump works in conjunction with a ram-airbox to improve breathing. Incoming air splits after the central entry duct, routing through twin side-mounted resonator boxes before reaching the carbs via the main airbox. This system further enhances the 600’s midrange torque by optimizing airbox resonance, and keeps the incoming charge cool by separating the intake airflow from engine and radiator heat, boosting power throughout the rev range. So effective is this cooling action that engineers opted to waterheat the carbs to prevent icing in cold weather.
The new YZF is said to have a 6-mph higher top speed than the old one, and while some of this is due to the more powerful engine, the bike’s streamlined shape plays an equally important role. Developed in a wind tunnel, the distinctive bodywork has a drag coefficient of just .275 (compared to the old bike’s .300), yet offers enhanced wind protection for the rider.
Ergonomics also have been improved with higher bars and a reshaped fuel tank. Though the steel Deltabox frame retains the same geometry (55.8-inch wheelbase, 25-degree rake and 3.8 inches of trail), the rear subframe is all new, yielding a slightly higher (31.7-inch) seat height and improved passenger accommodations.
Yamaha also upgraded the YZF’s conventional 41mm fork, making compression action more progressive near the bottom of its stroke. Both front and rear suspensions deliver excellent ride quality on the street and are fully adjustable, though the standard settings are near ideal. On a racetrack, the only glitch comes mid-turn at lower speeds, where it seems the fork packs up a little over bumps, making the wheel chatter slightly. Backing off the rebound damping doesn’t help much, maybe stiffer springs would.
As good as the suspension is, the brakes are even better. The four-piston Sumitomo calipers are one-piece castings with threaded alloy caps holding the pistons in place. If you picked up one of these exquisite components and examined it on its own, you’d be convinced it was built at significant cost by a metal artisan. Instead, it is a mass-produced part that transforms the T-Cat’s braking potential into something befitting a Superbike. The one-piece construction not only saves almost 2 pounds, it also provides a structure that is 16 percent stiffer than previous YZFs’ calipers, preventing the flex you get from some two-piece units.
The payoff comes when you brake for a corner for the first time at high speed-and find you’ve slowed too hard, too early. Try again, and you’ll discover how amazingly late you can brake into a turn without wondering if you’ll make
it around. The calipers, which work in conjunction with 11.7-inch rotors, are wonderfully responsive, totally effective and reassuringly safe.
Overall, the Thunder Cat is a definite step up from the old YZF, even though its claimed dry weight of 412 pounds is some 4 pounds greater than the old bike’s. This is thanks to the extra cladding and improved finishing of what is a much more sophisticated package. The bike is a well-engineered, well-thought-out response to the unique demands of the 600 sportbike class.
Because U.S. Yamaha put most of its eggs in the Royal Star mega-cruiser’s basket for 1996, because EPA testing takes a while and because Europe is Yamaha’s fastest growing 600 market (U.S. sales are flat), all T-Cat production will be targeted for Europe, at least until the EPA rigmarole is complete. But the Thunder Cat definitely is U.S.-bound. Says Yamaha spokesman Bob Starr, “We’re going to bring it in as soon as we possibly can. We’re chomping at the bit. We hope to have it within the next six months.” Translation? Expect both the YZF600R and its YZF 1000 stablemate in the U.S. this year as early-release ’97 models.
That’s really good news, because this is a watershed motorcycle. It merges the performance of the Kawasaki ZX6R with the user-friendliness of the Honda CBR600F3 to deliver the best of both worlds. Yamaha’s engineers can consider their mission accomplished. U
