Winston Churchill may not havf known Not that the H600 was a total much about motorcycles, but he was a master was just about unbeatable in production-class roadracing. at motivating people. Once, for example, to It's just that in the more important competition to get from rally his fellow Englishmen during the early, bleak days of World War II, he told them that they could "win the world through sacrifice."

Forty-six years later, Yamaha's new FZ600 is tangible, two-wheeled proof that Churchill was right, that through sacrifice comes victory. The FZ's world is that of the no-compromise sportbike; and after years of coming up second- or third-best in the mid-displacement sportbike wars, Yamaha's entry finally has what it needs to slam the door on its competitors. That transformation involved sacrificing some of the all-around flexibility possessed by the FZ's predecessor, the F.I600, in order to make this new machine the finest pure sportbike in the class.

Not that the FJ600 was a total loser.  In fact, that the bike was just about unbeatable in production-class roadracing. It's just that in the more important competition to get from the dealer's showroom to the customer's garage, the FJ ran into twin buzzsaws from Kawasaki and Honda. Both the Ninja 600 and the Interceptor 500 looked racier than the more-mainstream FJ600, and Yamaha found itself with a good middleweight sportbike that was setting records the racetrack but not on the sales charts.

Obviously, something needed to be done. But the catch phrase at Yamaha for 1986 is "Evolution, not revolution,' meaning that a new-from-the-tires-up bike was out of the question. That didn't prove to be a monumental stumbling block, however, because Yamaha already had the components in-house that it would need to build a world-beating, 600-class sportbike. The powerplant for the new bike, for example, would come right from the FJ600-although in a marketplace loaded with liquid-cooled engines and combustion chambers stuffed full of valves, the FJ's motor isn't exactly a technological wonder. The air-cooled, eight-valve inline-Four has been around since 1980, when it first appeared as a 400 for the Japanese home market. America got its first look at the engine in 1981, mounted in the Seca 550 sportbike.

So in all aspects, the FZ's engine is quite conventional. Double overhead camshafts are driven by a roller chain running through the middle of the cylinder casting. Valve clearances are adjusted via shims inside of buckets atop the valve stems. Two-piece connecting rods bolt around a crankshaft that turns in plain bearings. And in a move that was innovative five years ago but hardly earth-shaking now, the generator is mounted behind the cylinders, above the six-speed gearbox, allowing an engine width of just 16 inches.

Despite its rather unimpressive specifications, though, the 598cc engine has proven itself capable of propelling any chassis into which it has been wedged up to and often beyond class performance standards. But with the FZ600, it's the chassis that gives the bike its leg-up on the competition. For two years, this particular collection of rectangular steel tubes has been tearing up the backroads of Japan in near-legendary fashion, powered by a liquid-cooled 400 Four. And because the 600 engine is essentially just a bored-and-stroked 400, it was a simple matter to combine the best parts of FZ400R and FJ600 to come up with the FZ600.

That combination almost assured sportbike success, but it also forced the aforementioned sacrifices. For one, the FZ, thanks to its 400 heritage, is a small motorcycle, with a wheelbase that is almost two inches shorter than the FJ600's. Combine this with hiked-up footpegs and low-mounted handlebars, and you've got a motorcycle that painfully forces its rider to take straightline miles at legal speeds in small doses. Not helping matters at all is the thinly padded seat, guaranteed to make gas stops looked-forward-to events. But at least the rider's seat is better than the laughably under-padded vinyl rectangle that FZ600 passengers are required to perch atop.

Also adding to the sacrifices is a rear suspension that has been calibrated more for race-replica leaning than for smooth negotiation of city streets and expansion-joint-infested highways. Thankfully, the air-adjustable front suspension is wonderfully supple, responding to even the smallest bump or ripple in the asphalt.

Ridden at 55 mph for an extended amount of time, the FZ not only inflicts its rider with numb-butt, aching wrists and kinked knees, but also tingling hands and feet, for there is an annoying amount of vibration at that speed, in spite of rubber mounts at the engine's front attachment points. To be fair to the FZ, Yamaha's mid-displacement Fours have always been buzzy, and at least with this latest incarnation, the vibration diminshes dramatically as speeds get into the real-world realm of 65 to 75 mph. What vibration remains is far, far less than on the FJ600.

If the previous list of sacrifices seems too much for a bike to be saddled with, think again. Open-road complaints about the FZ are simply blown away after the first freeway off-ramp. When the asphalt starts to twist and turn, the bike comes into its own, and suddenly engine vibration goes unnoticed, the cramped riding position is transformed into the perfect backroad attack stance, and a harsh rear suspension becomes just right for those hard-left, hard-right maneuvers. In other words, sacrifices in normal riding turn out to be assets when the FZ is pressed to its limits.

And with this bike, those limits are high indeed. A trip down a familiar backroad on the Yamaha is an eye-opening experience. Usual braking points have to be revised or done away with altogether, and cornering speeds increase by impressive amounts. But best of all, the FZ accomplishes this without any added drama: It is an absurdly easy motorcycle to ride ridiculously quickly.

Due to its rigid frame, taught suspension and low, light weight - the FZ is 20 pounds lighter than the FJ600 and a whopping 33 pounds under a Ninja 600 the Yamaha is endowed with almost magical handling. Everyone who rode the bike, from backroad novice to national-class roadracer, came back with tales of light, pinpoint-accurate steering, of being able to change cornering lines at will, of going faster on a particular section of road than they had ever gone before.

Because the FZ600 easily devoured any backroad dish we could serve up, we took the bike to Willow Springs Raceway to see if faults would show up at race speeds. For the most part, none did. With the rear shock set on its lowest preload setting, the footpegs would occasionally scrape the tarmac. And the front fork, despite its variable damping valve that restricts oil flow during compression, still dove excessively when the brakes were applied hard. Setting the shock to its highest preload and adding five psi of air to the fork helped both problems. Our resident go-fast guy felt that the rear shock could use more compression damping and wanted heavier-rate springs in the fork, but he still felt the FZ would be a better choice for road-racing than the FJ600. That's about the highest praise possible, since he already owns the box-stock 600cc track record at Willow Springs - on an FJ600.

If there was one aspect of the FZ's performance that left us wanting more, it was the engine's output. At a claimed 68 horsepower, the new bike is down four bhp from the FJ600. although that deficiency is well masked by the bike's light weight and slippery aerodynamics. Yamaha says the FZ has been detuned slightly through 2mm smaller carburetors - to help improve the engine's mid-range performance; but the truth is that the frame's tight dimensions meant that Yamaha had to make sacrifices with both carburetor size and airbox volume. There simply wasn't enough room to fit the kind of free-breathing intake system the engineers would have preferred.

Luckily, the bike's drivability hasn't suffered. After getting past a none-too-strong low-end, the engine pulls cleanly and steadily to its 10,500-rpm redline. There isn't really a point in the powerband where things explode, but keeping the revs above 8000 is the best way to make time.

Albeit slight, the FZ600's horsepower deficit is the only chink in its armor. And having just announced a brand-new 400cc engine patterned after the FZ750 powerplant, Yamaha may be a simple bore-and-stroke job away from being able to shore up that part of the FZ600's performance envelope. Of course, with a new Honda 600 Interceptor almost certain next year, as well as a Suzuki GSX-R600 and perhaps even a revised Kawasaki Ninja 600, the FZ may need all the help it can get in 1987.

For now, though, on the strength of its marvelous chassis, the FZ600 is just about unbeatable. To borrow from Winston Churchill again, in the mid-displacement sport-bike battle, this just may be Yamaha's "finest hour."