by Neale Bayly
There has been a lot of excitement and buzz about the 600cc class this year, with all the major players rolling out new or improved machinery. Suzuki kicked it off with their latest GSXR when we traveled to Italy in March, and since then, Yamaha, Honda, and Triumph have unveiled their respective weapons. As the last to show their hand, Kawasaki chose the challenging Almeria racetrack and surrounding mountainous countryside of southern Spain, to introduce their latest weapon to the world’s media. Over the course of two days, we got to sample the ZX-6R in a variety of riding situations as well as attend the usual technical briefing to learn about the bike, and some Q and A with Kawasaki’s engineers.
For ’05, Kawasaki has stuck with their successful formula of offering the R model for the street with a larger 636cc engine, while their identical looking RR handles race duties with its class legal 599cc power plant. The RR also features a few minor chassis changes, a close ratio transmission, and other changes to better suit it for racing, but we weren’t in Spain to test it, so more about this one at a later date.
My time on the original 636 had been limited to a few track sessions, but I came away with good memories of a solid handling machine with good useable mid-range grunt and superb brakes. Talking with my fellow scribes at the launch, apparently harsh suspension was the bike’s Achilles heel, but I didn’t ride it off the smooth track so I can’t comment. What I can say is the new ’05 6R might just be the most perfect mid-range sport bike on the market. With no real 750cc class, Suzuki GSXR750 excluded, the next choice is one of the liter bikes. And, while the four cylinder bikes on offer in this category are absolutely phenomenal, they are all total overkill on the street and need some serious commitment for fast track work. The V-twin offerings are a little more practical, but come with a significantly higher price tag.
A 600cc on the other hand, while still ballisticaly fast, is a little more user-friendly for the street, and a lot less intimidating for track days. Sure they typically suffer from modest low and mid-range power, but the rush of adrenaline to be found approaching red line, while cog swapping as fast as possible, goes a long way to overcoming this. Not so anymore. The extra 36cc to be found in the Kawasaki 6R motor gives the rider some serious mid-range and low speed drive ability from as early as 3000rpm if needed. There is no pronounced step in the power, or holes in the power band, and the engine pulls strongly all the way till the shift light tells you its time to change up around 15,000rpm.
This year’s bike makes ten more horsepower than last year’s model for a quoted 136 at 14,000rpm with ram air assistance. This has been achieved with some significant work to the top end of the engine. Starting in the cylinder head, the ports are treated for extra smoothness, and larger valves are placed further apart to get fuel in and out faster. Opening and closing them, racing kit cams with increased profiles are used, while below the head the higher compression pistons have reshaped crowns and new low friction skirts.
To help with the power boost, larger 38mm throttle bodies are employed, and to allow them to be bigger without increasing the engine’s width they are now oval, which is a first in the motorcycle industry. Firing fuel into the bigger, more efficient throttle bodies is a dual injector system; utilizing extra-fine atomizers in the throttle bodies it has a set of secondary injectors in the airbox. A new centrally located, more efficient ram air system is now used to help the extra fuel do its job in the combustion chamber. The result of these changes is absolutely perfect throttle response anywhere in the rev range in any gear.
Our first couple of sessions on the track were ridden in damp, cool conditions, and there is never a more important time to have smooth throttle response. The system is so perfect, I was able to run low gears and high rpm to better control my corner exits, the small throttle openings needed to make forward progress giving instant, smooth trouble-free power on demand. Rolling off and back on the throttle again when needed was a confidence inspiring action, and allowed me to circulate the damp track with a fair amount of speed. If there were any problems to be found in the system, those first sessions would have most certainly showed them.
No prizes for noticing the new exhaust. With its fashion following under tail routing, it gives the bike a very clean and sleek look. What you can’t see is the internal exhaust valve. A first for a 600cc sport bike, an ECU reads engine revs and throttle position to determine when to open or close the valve. This helps the ZX-6R make better low and mid-range power, and only gets praise from this corner, especially on the rain soaked mountain roads around the Circuit Almeria during our street ride. The exhaust system also gets a catalytic converter for cleaner running.
Before moving on, there are a couple more things to note with the engine. First, a slipper clutch is now employed to help with premature down shifts. While I never needed it, it was a comforting thought peeling off speed from about 150mph down the back straight for the second gear right-hander that I couldn’t mess up by dropping gears too quickly. Secondly, the engine cases have been beefed up to handle the extra power, and a deeper sump is used to lower the amount of oil circulating around the moving parts in the upper end of the engine.
There are some slight changes in the transmission also with a new bearing on the shift drum locator arm for better shifting, a taller third gear, and needle bearings at the end of the transmission shafts for greater strength. I didn’t have any problems with the previous model’s gearbox and certainly didn’t experience any with the ’05. It shifts with silky smooth precision and no missed gears made it into my notebook over the two days.
Wrapping around the screaming 15,000rpm power plant is a new frame. Reduced in length by 13mm, it allows the use of longer swing arm, while also shortening the wheelbase 7mm. The rake is also tightened up half a degree, but the changes in no way bestow any twitchy handling traits on the 6R. Suspension duties are taken care of by Showa this year in an attempt to find more compliance. Featuring tough looking 41mm inverted cartridge forks up front, and a gas charged rear shock out back, the ride quality is second to none. Allowing the bike to literally float across the many surface irregularities to be found on the Spanish coastal roads, while not sacrificing any stability or cornering precision, I was very impressed with the set up. For the track, the suspension settings were firmed to deal with the higher speeds, and there were no disappointments to be found here either. The bike was extremely compliant, with no extra dive under hard braking or squat under equally hard acceleration, staying committed to my chosen line with the lightest push on the bars.
Attaching to the excellent forks are some of the best stock stoppers in the business. Radial mount Tokico four piston calipers bite down on 300m stainless steel petal rotors and simply inspire confidence. There are seriously heavy braking spots on the track, and chasing down a fellow hack, I made up a bunch of time on him in these spots. The front-end just stays planted, and the bike stops solidly in a straight line as the digital speedometer numbers drop almost as fast as they rise under acceleration. Aiding and abetting the process, a five way adjustable radial piston master cylinder pumps the necessary fluid to the pistons with little more than a light two-finger squeeze. There is a back brake also, but I can’t say I used it much, although I did try it to make sure it didn’t lock up too quick in the rain in case I needed it, and it has a useful amount of travel before that happens.
Taking a look at the lightweight under slung caliper, which also grabs a petal rotor, gives a good opportunity to check out the sexy looking satin black swing arm. Looking more like something from a Moto GP machine, your name is going to have to be Tommy Hayden if you are going to find any trouble with this beast.
It would be easy to think that all of this super slick hardware and increased engine performance would have pushed the ZX-6R toward a more radical ride position and ergonomics, but in actual fact the opposite is true. The seat now angles back and the bars are closer to the rider due to a more pulled back steering head. This allows you sit more “in” the bike, and it is actually extremely roomy for a 600cc machine, even bordering on comfortable out on the road. I was actually thinking a set of bar risers and some soft luggage could easily extend the 6R’s abilities to sport touring duties if needed.
The riding position also worked extremely well on the track, making the fast left/right transition through the hairpin a breeze. It also allowed me to tuck well down for the long back straight, and to circulate the track with a good degree of comfort. There is also an indentation in the gas tank to further allow the rider to get lower behind the screen on those mornings when you are late for work.
Visually, the bike is a little short of stunning from any angle, and all new bodywork, gas tank and wheels, that compliment the under tail exhaust, are responsible. And, as well as being a looker, the new ZX-6R is also more aerodynamic for improved top speed and acceleration. Designed to allow the air to pass over the rider in a smoother path, the gains are said to be the equivalent of adding ten horsepower.
For the test, the standard fitment Bridgestone BT014 radials were wrapped around the new wheels, with super sticky race compound BT002’s going on in the afternoon. The damp conditions in the morning didn’t allow us to push the stock tires, but on a dry track the 02’s allowed me to push as hard as I wanted without any drama. For track days, a set of these is a must.
At the end of my ride I noticed an ’04 in one of garages and, parked next to the new models, it was interesting to note how different the two bikes are. Softer, sleeker and with more flowing lines, it is also faster (the local track expert went 1.5 seconds quicker) with better handling and a more comfortable riding position. Is this the best 600cc bike on the market? Well, with the bigger motor giving so much extra mid range, the superb ergonomics, and a chassis and suspension package that is at least on par with anything out there, I have a strong feeling the Kawasaki ZX-6R will be top of the class this year.