Honda finally makes 600cc Race Replica

By Jim Duncan

Over the 16 years since its legendary 1987 debut, the CBR600F has won fame, acclaim and countless racing titles with its hard-hitting combination of light weight and strong, responsive performance.

Widely praised for its smooth, unruffled power delivery, the CBR has come to be relied on for providing the best of both worlds: easy manners and predictable performance for day-to-day riding coupled with race-winning potential at the most competitive levels of World Supersport competition.

However, as tastes have changed over recent years, and greater interest has been shown in the more intensive performance capabilities of the motorcycles in the 600cc Supersport class, especially as related to racing, the gap between the CBR600F’s traditional emphasis on top performance combined with easy, accessible street manners, and the narrow-focused performance required for circuit domination has steadily widened.

In response, Honda decided against totally upgrading the popular CBR600F to full race-ready spec, and thereby altering its position as the class’s finest and most effective all-round Supersport road bike.

Instead, they set out to create an entirely new middleweight class machine designed to meet the hyper performance requirements of the more focused competitive end of the class spectrum, while leaving the CBR600F to continue in its traditional role.

Styling

The new CBR600RR is nothing less than a road-going replica of Honda’s current new MotoGP racing champion, the RC211V.

Packed with a veritable plethora of leading technology gleaned from and proven on test tracks and racing circuits the world over, this new midrange class ‘RR’ also takes its styling cues from the most dominant force in MotoGP’s premiere season.

Unlike anything seen before on the street, and certainly unlike any of its predecessors, the new CBR’s fairing features a sharper nose with a much lower windscreen compared to the CBR600F and F/Sport, and a form geared much more to the needs of the circuit than to the comforts of the street.

Like the RCV, its smaller, more compact fairing achieves a fully optimised balance of the competing qualities of high-speed aerodynamic function and lightweight, instantly responsive control.

The CBR600RR’s newly designed fuel tank, or to be correct, its new fuel tank cover, is fully 70mm shorter in length than the tank on the CBR600F or F-Sport.

Based on a format conceived for and tested on the RC211V racer, this new design plays a fundamental role in the new RR’s compact configuration and swift, neutral handling, as it allows the rider to sit more forward, both closer to the steering head and closer to the machine’s overall centre of mass.

The actual fuel tank shares the space underneath the cover with the airbox, and makes a critical contribution to the new CBR600RR’s guiding concept of total mass centralisation.

The CBR’s sleek seat cowl also features lighter looking lines and smoother curves that flow back to terminate in a slimline LED taillight display that is lighter and thinner by half than the LED taillight featured on the CBR RR FireBlade.

The new seat cowl also mounts a small pillion seat pad that provides a comfortable enough perch—if necessary—for brave-hearted passengers.

However, this pad would probably best be left unoccupied to make the very most of the new CBR600RR’s hard-charging performance potential.

Beneath the seat cowl protrudes another highlight of the CBR600RR’s new design: its new Centre-Up exhaust system.

New Wind Tunnel-Tested Induction Ports

A major performance feature of the CBR600F for the last few years, the fairing’s large, forward-facing Direct Air Induction ports are now positioned outside and below the new headlights, where they continue to feed large quantities of cool, power-producing air into the large-capacity airbox now located under the forward half of the CBR’s new fuel tank cover.

Extensive wind tunnel and track testing found that such large intake ducts tend to impart a vague resistance to rapid changes in direction at full racing speeds.

This usually causes the motorcycle to feel almost as if it has locked onto target or cornering attitude. To counteract this phenomenon, the RR’s ports were made in a simple yet highly effective new twin layer design, with holes punched through the outer layer to allow air to ventilate through and break the ‘grip’ of the airstream rushing into the ports described by the inner layers.

As insignificant as this modification may seem just looking at it, the difference it makes on the RR’s high-speed handling and ‘flickability’ through a racetrack’s chicanes and similar manoeuvres is positively breathtaking.

Coupled with the new CBR600RR’s highly centralised mass and other race-bred improvements, high-speed handling is as lithe and responsive as imaginable, and overall control is taken another rank higher in performance.

New 4-into-2-into-1 Centre-Up Exhaust System

Certainly another eye-catcher on the new CBR600RR is the large single exhaust pipe looming menacingly out from under the rear of the seat like the afterburner on a jet fighter.

Following the lead of several of the world’s most competitive race machines, including Honda’s own RC211V MotoGP racer, this new ‘Centre-Up’ exhaust system snakes directly under the engine, then up and over the rear tyre to nestle its large-capacity stainless steel inverted isosceles trapezoid-shaped silencer in the specially sculpted space beneath the seat.

A big question for many who are contemplating the RR will be this: Can I install my aftermarket titanium Remus exhaust? If the new design hinders the installation of a slip-on can, Honda could well lose a lot of customers. Keep your eyes glued to the news section for more on this topic...

Back to the new-design exhaust system, and when you taken a side-mount pipe out of the airstream, the turbulence and related air resistance associated with said side-mounted pipes is eliminated, while nothing is left to get in the way of maximum cornering clearance.

An elegant solution to several design problems, and an exclamation point on the new CBR600RR’s hyper-aggressive new look.

Engine

The new CBR600RR is no mere styling exercise based on a higher-tuned version of the CBR600F’s well known and highly regarded engine.

Instead, its new ‘RR’ version powerplant was designed from the ground up to provide an all-conquering blast of track and street performance that will leave no mistaking who’s riding with the winners in 2003.

With a much more circuit-oriented mission dedicated to unrivalled racetrack dominance, the CBR600RR’s development team concentrated on refining the fundamentals of high-performance engine design with a host of major improvements and new concepts forged in the fires of Superbike and MotoGP competition.

Interestingly enough, extensive testing of various combinations of bore and stroke sizes found that the current CBR’s displacement figures were also ideal for the new ‘RR’s performance targets, so no changes were made to the engine’s basic displacement figures, which remain the same as the current CBR600F.

Instead, efforts were focused on achieving improvements in engine performance through both a smaller and lighter design, reduced mass and friction and more efficient combustion characteristics. This was ultimately achieved through two major changes in the engine’s design.

A Narrower Profile

With the goal of achieving a major increase in cornering clearance and banking angle, the engine’s width was reduced at the crankshaft through the repositioning of several key components.

First, the crankshaft’s starter gear was moved from its current location on the left, behind the ACG, to the right, which freed up room to move the ACG itself further inboard, and reduce the dimensions of its cover accordingly. The distance from the engine centreline to the outer perimeter of the ACG cover was subsequently reduced by 21.5mm.

This change alone, combined with a shift of the engine’s centreline relative to the centreline of the frame, and the newly designed ACG and clutch covers with their deeply tapered underside corners, effectively narrowed the width of the engine to realise a significant 3° increase in bank angles for each side, while ensuring more than ample cornering clearance at all-out racing speeds.

‘Nutless’ Connecting Rods

Connecting rods also play a big part in helping to achieve peak power-producing engine speeds, and excessive weight or mass here slows response and acceleration while introducing vibration and stress that can adversely affect operation at higher rpms.

The new CBR600RR’s connecting rods feature a lighter ‘Nutless’ design first pioneered on the VTR1000F and VTR1000 SP-2, which use standard threaded bolts screwed directly into tapped holes in the body of the rod, instead of the conventional nut and bolt combination used in most rods to hold their endcaps in place.

Requiring only one tool to assemble, the new design is 12g lighter than the conventional bolt and nut combination, for a total weight savings of approximately 35g per cylinder, or 140g overall.

This significant reduction in reciprocating weight makes a major contribution to reducing the engine’s mechanical load to help the new CBR600RR achieve a much more aggressively sharp feeling of responsive acceleration. The RR’s new connecting rods have also been carburised for an ultra-hard outer surface that ensures an optimal balance of strength and durability over the course of riding and racing extremes.

The end result of all these improvements is a quicker-revving engine that produces strong power throughout its wide rev range and almost instantaneous bursts of blistering acceleration.

Next-Generation Dual Sequential Fuel Injection System (PGM-DSFI)

Fuel and air management has come a long way in a few short years, with the latest fully mapped and digitised fuel injection systems not only providing quicker starts, sharper response and more powerful performance, but achieving all this while consuming far less fuel and releasing far less in the way of harmful exhaust emissions.

Great strides have also been made in delivering smooth and steady low-speed performance for smaller, mid-displacement engines, with comfortably linear control in the lower revs making a major contribution to easier driveability in urban traffic conditions.

However, while current systems provide excellent performance for most on-road riding applications and engine speeds, the new CBR600RR was, from its inception, intended to deliver strong power all the way up to a blazing 15,000rpm power peak.

At such engine speeds—and incredibly short intake and exhaust stroke intervals—the limits of current fuel delivery system configurations were soon found.

Specifically, while fuel injected into the intake ports at close proximity to the opening valves does provide excellent response and strong power output at low-to-midrange operating speeds, at higher intake velocities the fuel spray simply doesn’t have enough time or distance to fully atomise and adequately mix with the in-rushing air to provide the optimum air/fuel mixture needed for efficient combustion, and thus strong power output.

To counteract this phenomenon, the CBR’s engine design team first tested and then installed another full set of four 12-hole injectors, positioning them high in the roof of the airbox.

This second set of injectors has been programmed to only operate when the throttle is opened wide at engine speeds of approximately 6,000rpm, resulting in a significant boost in fuel intake and combustion efficiency at high speeds.

Opening a tiny fraction of a second before the main injectors on each intake stroke, this auxiliary set of injectors primes the air rushing into the velocity stacks of the lower throttle bodies with a more finely atomised spray of fuel.

This highly accelerated air/fuel mixture is further enriched by the normally timed injectors installed in the new larger throttle bodies (up from 38 to 40mm), which release a precisely modulated volume of fuel into the mixture rushing into the combustion chambers to ensure stronger, more complete combustion at high engine speeds.

Another important benefit of this new system is that the pre-charged induction also significantly cools the air flow through the throttle bodies and intake ports.

This results in a much denser charge of air/fuel mixture into the chambers than could otherwise be achieved in a normally aspirated engine at such a blazingly fast intake stroke interval—at 15,000rpm, a mind-boggling 125 openings and closings of each intake and exhaust valve every second.

Chassis

Besides high power and light weight, perhaps the most fundamental factor affecting the design and optimum performance of any sports-oriented motorcycle is the way its weight is distributed.

Since motorcycles, unlike cars, bank and turn around two axes—an ‘earthbound’ variation of the roll and yaw characteristics one associates with aeroplanes—any excessive weight or mass positioned near the machine’s outer extremities exerts a strong inertial influence on—and resistance to—its ability to swiftly lean and change direction.

Thus, nearly all recent racing machines and many high-performance Supersport motorcycles have come to be designed with a growing emphasis on the concept of mass centralisation.

Like the RC211V from which it receives its primary design influence, the totally new CBR600RR features a more compact form designed primarily for racetrack dominance.

Its uniquely constructed new frame, innovative chassis layout and advanced, MotoGP-class suspension system combine to provide an unprecedented level of performance and almost paranormal response that will soon be shedding seconds off lap times from Suzuka to Silverstone.

Optional Equipment

The CBR600RR will also be released with an assortment of optional parts that have been specially designed and produced by Honda Access Corporation to improve upon aspects of its road and track performance. These include:

• A motion-and vibration-sensitive alarm system that emits a piercing wail if tampering is detected.

• A slip-on moulded plastic pillion pad cowl that clicks into place to give the new CBR600RR a more singularly sporty and purposefully competitive look on par with its new level of performance.

• A specially selected U-lock designed to fit into the compact U-lock carrier space located under the pillion pad.

Optional HRC Racing Kit

As it has for the VTR1000 SP-2 and many of Honda’s other production motorcycles that vie in amateur and world-class racing competition, Honda Racing Corporation (HRC) is releasing an extensive array of specialised racing parts for the CBR600RR.

This complete racing kit includes engine, chassis, suspension and body parts designed for stronger power, lighter weight, sharper handling and better aerodynamics to hone the new RR’s capabilities to a finely tuned competitive edge, and focus every aspect of its performance potential on the twin goals of competitive World Supersport racing capability and ultimate victory.

So, when all is said and done - can the CBR600RR take the fight to the current kings of 599cc racing - the Suzuki GSX-R600 and the Yamaha YZF-R6? We'd have to say yes, though keep an eye out for the an all-new Kawasaki Ninja, designated ZX-6RR, as well.

With all the tweaking and fiddling for extra power that Honda has been doing, expect Suzuki, Triumph and Yahama to create similar hi-po homologation specials in the near future. As it stands however, the new CBR600RR is one sexy piece of kit - mayhaps it's time to trade up...