Yamaha Yzf-R1
YAMAHA YZF-R1
CW FIRST RIDE
Chips ahoy!
DON CANET
IT'S TOUGH TO FOOL THE PEOPLE, ESPECIALLY WHEN THE PEOPLE have access to dynamometers. Yamaha's signature five-valve per-hole Genesis cylinder-head design had served the company's sportbikes well for 20 years, but it was time for a change. The problem was midrange torque—or lack thereof. With the 2007 YZF-R1 `s new four-valve chambers, compression ratio is up to 12.7:1 and torque is said to have fattened nicely in the middle revs. In the past, Ri torque has peaked up above 10,000 rpm, giving a narrower powerband than the competition, whose torque generally peaks at 8500 revs. With a tuning shop seemingly on every street corner these days, everyone could see the deficien cies in the YZF's dyno chart.
Street cred was not helped by the lack of a factory Ri in AMA Superbike racing. Both problem areas have been addressed for `07, as Yamaha USA made its demands known during the new bike's planning and testing phases. Evidently, Yamaha's European importers placed greater emphasis on peak power production, whereas the American arm requested power delivery that was meatier in the midrange. Yamaha’s engineers answered the call, giving the new R1 a broader torque spread and smoother power delivery, while improving the top-end punch we’ve known in the past. Yamaha’s latest technology now fuels the literbike fire with Yamaha Chip Controlled Throttle (YCCT), the fly-by-wire throttlecontrol system that debuted on last year’s YZF-R6, but with the four throttle bodies upsized to 45mm. The tuning-fork folks upped the ante, though, by chipping in with another technical innovation that addresses the tradeoff engine tuners have traditionally faced in settling on a particular velocity-stack length. The Yamaha Chip Controlled-Intake (YCC-I) system offers a clever solution to obtaining both the low-to-mid rev performance of a long intake tract and the peak performance boost of a much shorter tract. Overall intakefunnel length is 140mm until engine revs exceed 10,400 rpm with the throttle more than 57.5 percent open, at which point an electric motor quickly lifts away the upper portion of the split velocity stacks, reducing the effective length to 65mm.
The new Rl’s 998cc liquidcooled inline-Four still looks familiar but breaks long-standing company tradition by no longer employing the 20-valve cylinder-head arrangement that’s been a heralded family trait since its debut two decades ago in the FZ750 engine. Eliminating the center intake valve-with the stem set at an off angle from its flanking mates-has made for a much smoother combustion chamber and piston-crown shape. This has resulted in improved combustion efficiency and cleaner burning, as well as enabling the compression ratio to be bumped from 12.4 to 12.7:1. Intake valves have grown from 23.5mm to 31.0mm in diameter and are now made of titanium while the steel exhaust valves remain
unchanged from last year. Valve lift sees a substantial increase from 7.6mm to 9.2mm on the intakes and 7.5mm to 8.3mm on the exhaust side, along with revised valve timing said to promote stronger acceleration from low rpm.
Prior to our track test, I wondered if this sudden shift in tune could be felt from the saddle. That opportunity would be put on hold the following day as we arrived at a rain-soaked Laguna Seca Raceway. While waiting for the track to dry, I had a chance to examine parts laid out on a table in the pit garage. The R1 now has a slipper clutchonly available on the R1 Limited Edition last year. The interesting thing here was the trio of tensioning springs used to tune the amount of slippage allowed during deceleration. I learned that for racing and hardcore trackday use, riders can remove a spring to further reduce engine braking from the standard setup. To improve durability and promote smoother engagement, a rib has been cast into the new clutch basket that helps direct more engine oil onto the clutch plates.
Thanks to a stiff breeze and a few breaks in the cloud cover, we got in three hours of track time following lunch. While working heat into the standard Pirelli Diablo Corsa radiais, I took the opportunity to conduct roll-ons from low rpm in the higher gears. While the R1 doesn’t appear to match the low-end grunt of the Kawasaki ZX-10R or Suzuki GSX-R1000, there’s a notable degree of improvement over last year’s bike. Em certain the gain must be experienced on the street to be fully appreciated and the final verdict must await back-to-back comparison testing.
Another item of note was the precision and control I felt through the throttle as the pace increased, allowing me to flirt with the limits of cornering grip without any sudden surprises. Even though I found myself running high revs in second gear through several of the track’s 11 turns, the Rl’s YCC-T and minimal drivetrain lash allowed me to do so with a great degree of confidence. In the later sessions I began pulling third gear through some of those same corners without any detectable loss in acceleration on the exit. Keeping the engine spinning at or above 8000 rpm provided all the drive I was prepared to handle.
The chassis felt ready for more. Thorough revisions to the Deltabox aluminum frame were aimed at optimizing its rigidity balance. This also entailed a more flexible fork held in a more rigid steering-stem/triple-clamp assembly and a new 16mm-longer truss-style aluminum swingarm that’s stiffer torsionally but softer laterally for more give at deep lean angles. Main frame-spar rigidity, meanwhile, has been substantially reduced. Goals were improved turn-in and mid-corner front-end feel, as well as boosting cornerexit traction.
The suspension has received attention as well, with the 43mm KYB inverted fork getting a slight increase in spring rate and improved internals for more consistent damping. The Soqi-brand shock now offers highand low-speed compression-damping adjustment in addition to the usual rebound and preload options. Revised linkage provides more progression and increased firmness deep in the rear suspension’s travel. Another, cool (ahem) improvement is the relocation of the exhaust collector and catalyzer to outboard
of the swingarm, moving it away from the shock body. Aside from an occasional gust of wind catching the side of the bike as I crested the rise on the climb toward Laguna’s famed Corkscrew, chassis stability proved solid if not completely rock-steady. The suspension did a good job soaking up the track’s few bumps and undulations, while the cross-mounted steering damper kept all wiggles and shakes in check. Yamaha’s testers claim a distinct reduction in steering effort can be felt compared to last year’s bike.
I didn’t have the luxury of a back-to-back comparo but wouldn’t dispute the claim. The front Pirelli Diablo Corsa has been built to Yamaha’s spec and is lighter than the standard over-the-counter version. This, along with the RI ’s use of 10mm smaller, 310mm-diameter brake rotors, accounts for a significant reduction of inertial weight up front. The rotors are the same thickness as before but attention to detail is evident in the weight-reducing groove machined in their outer edge and use of thinner, lighter buttons to attach the discs to the carriers.
New radial-mount six-piston Sumitomo calipers have maintained outright braking power despite the reduction in rotor diameter, while the caliper’s separated four-pad design equalizes pad wear and resists backing-plate warping. The same Brembo radial master cylinder is used to good effect with excellent sensitivity and a moderate two-finger squeeze providing all the stopping power my forearms could bear. Charging deep into Laguna’s downhill Turn 2 put the brakes and the engine’s slipper clutch to the test, both of which passed with flying colors. Throttle blips during downshifts have been relegated to an optional exercise, as I never encountered any rear-wheel hop even when banging down through multiple gears.
Just as Yamaha’s EXUP exhaust valve-still in use on this Rl-is a Yamaha innovation that’s become commonplace on many modern sportbikes, you can wager the competition will soon chip in with their own variants of the new features this bike has introduced to the mass-production Superbike. The competition probably won’t have a choice in the long run, because the new Rl-for all the advances it brings-works. □
For additional photography of the Yamaha YZF-R1, visit www.cycleworld.com
