Motorcycles capable of winning world championships in near-stock form are not easily improved. But nobody knows the fine art of refinement better than Honda. Where the previous 600RR boasted a power-to-weight ratio of 3.76:1, the new bike pushes 3.58 pounds for every horsepower, thanks to its nine-pound weight reduction.
Shaving this weight was an exercise in counting ounces for Honda engineers, and almost no component large or small was left untouched. The new frame, featuring thinner wall sections in strategic areas, saves 3.6 pounds, while the new subframe shaves another 17.5 ounces. A new swingarm is lighter by 4.4 ounces, primarily because the upper shock bracket in the Unit-Pro Link(tm) suspension system is now cast into the swingarm, replacing last year's bolt-on piece. The new two-piece shock body is shorter and lighter than last year's unit, and features an aluminium spring-adjusting collar in place of last year's steel adjuster for even more weight savings. At the business end of the swingarm, the new 600 features a push-type chain adjuster like the CBR1000RR that is both lighter and stronger than the previous model's pull-type adjuster. A CBR1000RR-type master cylinder also saves weight in the rear.
More weight savings come through a new exhaust system that is 20.1 ounces lighter than last year's system, despite the addition of a catalytic converter. A redesigned and dramatically simplified rear cowl/seat section eliminates nearly a dozen components and also positions the seat-release key between the cushions for easier operation. Up front, a gull-wing-type top triple-clamp allows shorter fork tubes for weight savings, and a shorter axle trims more weight. Honda engineers even managed to trim weight out of the seat assembly, and even lighten the sidestand bracket. The drive sprocket was machined to save weight. Even the clip-on handlebar bosses and footpeg brackets have been made thinner and lighter to save a few ounces.Power to the people
Hidden away beneath the swoopy new bodywork, the CBR600RR powerplant retains the same basic architecture-a 599cc liquid-cooled fuel-injected in-line four cylinder that redlines at 15,000 rpm. This engine is amazingly compact thanks largely to a layout that places the mainshaft above the crankcase split line, thus allowing the countershaft to move closer to the crankshaft. This compact engine length (236mm) allows the engine to be positioned far forward in the chassis, in turn moving the rider compartment forward for more precise handling.
For 2005, there have been subtle but significant changes to the CBR600RR engine that have radically reshaped the power delivery. Like the CBR1000RR, the skirts of the 600's slipper pistons are now impregnated with molybdenum to create a friction-reducing surface, an innovative treatment both tougher and longer lasting than the LUB coating used previously. More than a surface coating, this process literally shoots particles of pure, low-friction molybdenum into the skirts of the piston with such high force and temperature they become embedded in the surface of the aluminum with a chemical reaction that bonds the material together. These pistons stroke through aluminum composite cylinder sleeves impregnated with ceramic and graphite for further friction reduction and superior heat dissipation.
With engine redline perched at a stratospheric 15,000 rpm, the interval between intake strokes shrinks drastically on the CBR600RR. The original 600RR addressed much of this fuel feeding challenge with Honda's Dual Stage Fuel Injection (DSFI) system, which features two sets of four injectors. In addition to the traditional port injectors, DSFI also employs showerhead injectors in the roof of the airbox to enrich the air/fuel charge during the abbreviated intake cycle, kicking in at speeds above 5500 rpm.
For '05, the 600RR gets new injectors (still featuring 12-holes as before) that flow more fuel more quickly. These injectors send a finely atomized air/fuel mixture through reshaped intake ports that now feature a narrowed venturi section, a carefully shaped area that increases the velocity of the fuel charge to promote more rapid cylinder filling. This addition, along with new EFI and ignition mapping, and a center-up exhaust system featuring a four-into-two-into-one design for increased performance, aerodynamics, and lighter weight, drastically alter the way this CBR makes power.
Without sacrificing any of the meaty punch high up in the rev range, the 2005 600RR begins to pull much earlier. Now a noticeable hit comes at about 7500 rpm, with the bigger jump about 1000 rpm later. As a result of this additional torque down low, the '05 engine feels much bigger than its displacement indicates, yet it still revs out to redline with the same kind of quickness and ferocity as the previous iteration. Net result: the new CBR600RR accelerates harder sooner in the powerband, giving riders more gear choices and making it easier to rip on even the tightest, kinked-up backroads you can find. Already a winner on the race track, the new CBR600RR is now a much better partner for street-oriented sport riding.
An all-new chassis makes this second-generation CBR600RR the class of the class.
The CBR600RR's fine die-cast aluminum frame is still manufactured using innovative casting methods to provide optimum rigidity and flex characteristics where needed. But the new frame features thinner wall sections to save weight and further fine-tune handling.
Bolted to the front of this frame is a massive new 41mm inverted Honda Multi-Action System (HMAS) cartridge fork featuring separately adjustable spring preload, rebound and compression damping. Designed not only to provide added rigidity and a significant reduction in unsprung weight, this state-of-the-art inverted fork also accommodates the RR's new four-piston Tokico radial-mounted front brake system. Because these massively powerful race-style calipers-squeezing 310mm floating discs-bolt into distinctive turret-type mounts similar to those introduced on the CBR1000RR, the calipers can better resist the shear forces generated under braking for less deflection and a stronger, more rigid set-up. This new configuration also creates space for a centrally located tightening bolt to help hold the two halves of the caliper together, and this new three-bolt design produces a more rigid caliper for improved stopping power, more even pressure distribution, and exemplary feel through the lever.
In back, the CBR600RR boasts the most advanced suspension system this side of a MotoGP grid. The innovative Unit Pro-Link rear suspension system, introduced on the 2003 CBR600RR and also used on the CBR1000RR, is patterned after the RC211V GP racer. In this system, the upper shock mount is contained within the swingarm rather than the frame. With no top frame-mount for the shock, this unique system reduces the transmission of negative suspension energy into the frame, allowing engineers to optimize frame rigidity and producing improved rideability out of corners. Just as importantly, this system clears room in the chassis for a fuel tank mounted low and close to the engine, adding to the RR's centralized mass. By integrating the upper mount into the swingarm's construction for 2005, this lighter and more compact design greatly facilitates rear damper maintenance by making possible quicker and easier access, while having fewer parts to contend with.
The CBR600RR's steeply angled nose also contains revised ram air ducts now more cleanly integrated into the aggressive lines of the bodywork. Above these ducts are redesigned Line Beam headlights, which are subtly redesigned with a sharper, more arresting image. These low-profile units feature compact, high-illumination multi-reflector designs projecting through clear lenses. Less than half the height of the headlights seen on most road bikes, these ultra-sleek beams provide a brilliant night-time view of the road ahead.
Other changes have shaped the CBR600RR's epidermis. The new, shorter tail cowl now combines with a new set of matte black side covers to provide a lighter and slimmer profile that also enhances rider mobility. The combination of new tail cowl and side covers also weighs less than the one-piece unit they replace, and the tail cowl's new centrally positioned pillion padlock located directly behind the rider's seat provides easy access to the under-seat storage area.
More weight savings can be found inside the CBR600RR's cockpit. The new RR's compact, fully electronic instrument panel is one of the slimmest and lightest ever mounted on a street bike. Positioned on either side of its large, central tachometer are a compact LCD display for fuel level and coolant temperature, and a large LCD readout of speed, dual tripmeters and related warning indictors. Brilliant ISO-marked LED indicator lights are positioned around the perimeter of the panel. When the ignition key is switched on, the CBR600RR comes alive with an eye-catching start-up routine that flashes the instrument panel's indicators and sweeps the tachometer needle.
Balancing Outer-Limits Performance with the Real-World Experience
It is rare to see engineering capable of enhancing a bike's outer-limits racing potential while also refining and benefiting the real-world street riding experience, but this is exactly the balance Honda engineers struck with the 2005 CBR600RR. In the highly competitive 600 sport bike marketplace, where increasing performance often means narrowing a machine's focus, the new CBR600RR casts a wide performance net just as certain to snare the imagination of street riders as it is to capture more championships in 2005.
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