Yamaha Yzf600
YAMAHA YZF600
1994's HOT TIP IN THE MIDDLEWEIGHT CLASS?
LOST IN ALL THE CONSIDERABLE HOOPLA SURROUNDING THE introduction of the RC45 is the fact that another equally important sportbike was just introduced. Unlike the ultra-expensive. ultra-rare Honda RC45, enthusiasts will actually see some of these, and maybe even get to ride an example or two. It is, of course the Yamaha YZF600, and it represents an important step forward for Yamaha.
The 1989 FZR600 brought Yamaha sales success and race glory, but time and product development move forever ____________________________ forward. B~y 1991, the
600 class had been kid napped by Honda's CBR. For the next three years Yamaha sat on its increasingly dusty laurels, while even Kawasaki turned up the heat last year with a greatly improved ZX-6 that hauled Miguel DuHamel to an AMA supersport champion ship. Finally the word came in time for the `94
model year: It was time to design and construct a CBR/ZX6-beater. To take up this challenge the new YZF600R carries nothing radical-just good development.
Sales of its bigger brother, the YZF750, have been quite good in Europe and Canada, and that fact influenced the designers of the 600, which inherited the good looks of the 750; taillight, fuel tank and seat are identical. The fairing is the same endurance-based unit, but—as we discovered during the bike’s European press introduction in Jerez, Spain, in December-tall enough to move high-speed air over the rider’s shoulders. This also leaves plenty of space for clambering over the tank and tucking in when called for.
Mirrors that actually work are a wonderful surprise, while the twin cat’s-eye headlights are a nice touch. The screened vents near the front tumsignals appear to have no function other than to provide minimal extra flow to the larger-capacity radiator.
The YZF’s riding position is surprisingly comfortable, given the bike’s performance-oriented mission. The pilot sits fairly upright, and finds only a modest stretch to the clip-ons, causing very little pressure on the wrists at slow speeds. No complaints about the seat, either.
The old FZR600 had a steel frame, and so does the YZF, which uses steel instead of aluminum to help keep the bike’s price to acceptable levels. Depending upon the plane in which it’s being measured, the new frame is between 85 percent and 146 percent stiffer than the old bike’s. The engine, hung at a 35-degree forward slant, now becomes an integral part of the frame, dispensing with the old bike’s front downtubes-this probably is responsible for a weight savings of a couple of pounds. The steel swingarm, a meaty Deltabox item, is similarly rigid. Production racers will be pleased to learn that the rear half of the subframe is detachable, making it easier to replace this section, which is vulnerable to crash damage.
No crash damage, however, at the Jerez circuit, where the biggest test of chassis (and rider) is the uphill right after the start/finish straight. A fast entry means a very fast exit, banked over, dragging the footpegs and drifting onto a patch where both tires slide, and then grip. When this happens, the YZF flicks upright, and while accelerating you have to pull the bike back down. But no tank-slap or wobble exaggerates your heartbeat here, even though this bike’s wheelbase is four-tenths of an inch shorter than the FZR’s.
Bikes at the Jerez introduction were shod with Metzeler ME Zls (120/60 ZR17 front, 160/60 ZR17 rear), and very good they are, too. Unfortunately, no one could confirm what the production bikes will wear, but if it’s the rumored Bridgestone BT50s, there’ll be nothing to complain about.
Discs and calipers are unchanged for ’94, but the master cylinder has been revised so it doesn’t give the instant grab of old. Also revised is the lever-this is now an adjustable item.
Track testing produced just one problem with the stock set-up: understeer. In long, fast comers, the bike tends to run wide of the chosen aiming point. To keep the bike on the line you want, constant pressure on the bars is required. The cure for this is a simple one. Raise the tubes of the new 41mm fork three-tenths of an inch and leave preload standard (four adjustment lines out of seven). At the rear, increase preload to five of seven notches (standard is three) and leave rebound damping alone. The difference is instantly noticeable. The fork was more stable on the brakes, and the front wheel felt planted under braking and hard cornering because of the forward shift in weight. A frazzled tread all the way to tire’s edge proved that the front ME Z1 had been worked harder.
If the YZF s chassis is excellent—and it is—the engine is even better. Apart from being a four-cylinder four-stroke, the engine bears little resemblance to previous models. The most discussed change is to the block; cylinder walls are no longer cast steel liners, but instead are straight aluminum bores coated with a ceramic composite—a process similar to Nikasil plating. Advantages, Yamaha says, include less weight, tighter clearances and cooler running. Disadvantages include non-availability of oversize pistons. Racers, desperate for every square centimeter’s-worth of gain, may see this as a problem. With squat, short-skirted pistons, bore and stroke is now 62 x 49.6mm to make 598cc.
Cylinder-head components are nothing outrageous. Everything s just a little lighter and more compact, surrounding the usual 16-valve head. This is aided by an increased-flow airbox and 34mm CV carburetors (the FZR used 32mm carbs) feeding fuel into shorter inlet tracts. The exhaust is now a 4-2-1 with large-bore headers to help boost midrange and top end. All this results in a free-revving engine with a wide power spread. Claimed torque is 48.5 foot-pounds at 9500 rpm with max power of 98.6 horsepower at 11,500, equalling the claimed output of Suzuki’s RF600R, Kawasaki’s ZX-6 and Honda’s CBR600F2.
Moving off idle, the engine pulls cleanly, with no sensation of over-lean carburetion at low revs. It’s when the tach needle moves around to 6250 rpm, though, that things really
start to happen, with power flattening at an indicated 11,750 rpm-1250 below the 13,000-rpm redline. Gearchanges through the six-speed box were positive and clunk-free, and despite the abuse it got, the new, larger clutch assembly remained intact, with none of the overheating and snatchy action exhibited by the old FZR showing through.
So has the YZF got the 600 class whupped, you ask? Impossible to say without a back-to-back comparison, and in the U.S. that will have to wait. The bike isn’t scheduled to be in dealerships until mid-summer as a 1995 model. For now, one thing is clear: At one time, the deposed FZR was the middleweight sportbike because of its punchy power delivery and brilliant steering. This new YZF maintains the FZR s promise and adds to it a healthy dose of horsepower. That may be a tough combination to beat. —Trevor Franklin
Trevor Franklin is Road Test Organiser at Performance Bikes, one of our favorite British motorcycle magazines.
