2005 Kawasaki ZX-6R
Almeria Spain, 12/15/2004 ~ 2005 marks the 20th anniversary of the GPZ 600R Ninja and the birth of the 600 Supersport class. Since that fateful day twenty years ago, the 600 class has been defined by constant improvement and a controversial trend towards narrow focused racetrack oriented sportbikes.
In 2003, Kawasaki fired one of the loudest shots in the 600 class, when it introduced the extremely aggressive ZX-6RR and 636cc ZX-6R. That ZX-6R made 108Hp at the tire, shading its competition by over 4Hp and scaring its riders with a razor sharp focus that translates into a nervous front end and a punishing ride on anything but the smoothest pavement. Still, its sizable horsepower advantage allowed it considerable sales success.
Not content with dominating the horsepower wars, Kawasaki has decided to refine the 6R's street manners, in an effort to challenge the more comfortable Yamaha R6 for top Supersport "Streetbike" honors. Because Kawasaki claims that the ZX-6R is aimed at street and track day riders, while the ZX-6RR is a limited production motorcycle aimed squarely at roadracers, the all-new 2005 ZX-6R receives special revisions aimed at improving its comfort and overall suitability as a streetbike.
Most notably, these revisions include a more linear powerband, flatter and more comfortable rider's seat, a slight relaxing of the old 6R's nervous steering geometry and an under tail exhaust. In addition, Kawasaki switched from Kayaba to Showa suspension components, softening the old 6R's (overly harsh) dampening in the process.
They also relaxed the riding position, changed the wheels to a lighter and stronger 6-spoke design like the ones on the ZX-10R, changed the brake rotors to a "petal" design (also like the ZX-10R), upgraded the master cylinder to a radial-pump unit, completely redesigned the frame, bodywork, intake and about twenty other things and generally refined the old bike into a nicer package. Kawasaki claims that these changes add around +3Lbs to the bike. Oh yeah, lest you think the ZX-6R is growing "soft" on us, consider this amazing fact: Kawasaki also redesigned the engine and they now claim that the 2005 ZX-6R has gained Nine horsepower.
"The 2005 bike should be putting something in the neighborhood of 117Hp to the ground!"
Since the previous generation ZX-6R made an honest 108Hp at the tire, the 2005 bike should be putting something in the neighborhood of 117Hp to the ground! Folks, I don't care if the thing has ape hangers and foreward controls, if it weighs less than 420Lbs wet and generates 117Hp, nobody is going to call it "soft".
Now that horsepower cat is out of the bag, let's discuss how Kawasaki achieved this stunning output from a mere 636cc of displacement. The obvious changes are the typical hot rodder tricks of higher compression and better breathing. To be specific, the 6R's intake throats have developed an oval cross section, allowing the total volume of airflow to increase, without increasing the actual diameter of the throttle bodies.
This prevented any frame widening to accommodate a wider throttle body rack. Immediately upstream of that rack sits a quartet of new "shower" type injectors, which come on-line above 5,500RPM to supplement the flow from the standard injectors. Once the mixture is properly enrichened, it enters a new cylinder head, which has been enhanced with a smoother surface treatment.
Those smoother intake passages lead to a set of +1mm larger intake valves and once inside the combustion chamber, the mixture is compressed 12.9:1 (up from 12.8:1) by a new set of deeply crowned pistons with low-friction skirts, before igniting and being expelled through a set of +1mm larger exhaust valves. After exiting the engine, the gasses travel to a catalytic converter and then out through a new flapper-valve equipped under-seat muffler.
That computer-controlled valve is closed until around 5,500RPM (depending on throttle opening, etc.), increasing backpressure and boosting low-mid RPM torque. Above 5,500RPM, the valve opens an additional passage through the muffler, to allow the deeper breathing necessary for good high-rpm performance. In a reversal of SOP, Kawasaki moved the cylinders into a more upright position, reducing their foreward-cant from 25° to 20°. Other engine revisions include the addition of a slipper clutch like the one on the ZX-6RR, and a deeper oil sump with a revised pump, to reduce crankshaft windage and cut parasitic drag.
Day 1 - The Street
All that power is well and good on the racetrack, but on public roads, it's the powertrain's refinements and the integration of the whole package that impresses most.
Though it is a cold morning, there is no need to pull any "cold start" levers, because the '05 bikes now feature an auto fast-idle circuit in their ECU. This means the ZX-6R fires-up with a minimum of fuss and quickly adjusts its idle speed to suit the engine's temperature. The Spanish countryside received a pounding from Mother Nature in the days preceding our visit, so the roads are mostly filthy and wet. As I accelerate away from the racetrack and out into the foothills, the new 6R quickly has me relaxed, because the throttle is delivering exactly the level torque that I request, so traction management is a breeze and the wet roads quickly fade to the back of my mind.
Between the flapper valve and the addition of those shower injectors, Kawasaki has managed to flatten the torque curve, creating a nice and linear power delivery, that pulls very hard through the midrange and then screams into the stratosphere. The changes are quite noticeable, though not what you would call "dramatic", thanks to the linear manner in which the torque is metered out.
After a few corners, it is immediately apparent that the shift quality and drive lash have been improved upon over last year's model and the new slipper clutch works like a charm. I would rate the shift quality as outstanding, very smooth and with a minimum of lash, slop or pedal travel. Of course it's no VFR, but this is one highly refined supersport.
The day's street ride, has us following a pre-determined route to various photo points and I enjoy the scenic views, as I cruise along between 50-260Kmh, depending on surface conditions and weather or not there is another vehicle within three miles of me. Spain is different indeed. After a few photos, I need to make-up some time on the rest of the group, so I find myself hustling through a nice set of twisty pass roads, where the conditions vary from soaking wet to sunny and dry, depending on what side of the mountain you are on.
"The stakes are high enough to make me a bit nervous.."
The stakes are high enough to make me a bit nervous, but the bike is happy to oblige whatever my ego or cowardice decide to dish-out. In these conditions, there are three things in particular that I appreciate about the '05 bike.
1.) The new Radial-Pump Master Cylinder offers very good feel and allows me to meter braking forces with the same accuracy that the fuel injection delivers acceleration.
2.) Kawasaki relaxed the steering geometry from 24.5° to 25° and extended the trail from 95mm to 104mm, so that the bike has less of a tendency to headshake over rough pavement, than last year's bike.
3.) When they switched from Kayaba to Showa suspension components, they specified softer damping for the forks and shock, so the ride is smoother and less prone to chatter.
Now that I've been in the saddle for a while, I'm starting to appreciate the flatter seat, and more relaxed riding position. Although the pegs are in the usual (high) place, I find that overall comfort is excellent for a supersport bike.
To be fair, I didn't spend any time droning down a freeway or trolling through traffic, so a thorough evaluation of the bike's comfort level will have to wait for a stateside test. However, I do think it's safe to say that the new ZX-6R is at least as comfortable as any other supersport that I've ridden.
600 Class "Streetbike" Score: A
After our street ride, we met back at the Circuito de Almeria, for a short (wet) track session. Since we didn't have any full-wet race tires, conditions dictated that we keep the speeds moderate. Once again, the supple suspension, linear power delivery and predictable brakes kept the drama to a minimum.
Though we didn't really do much hot lapping, I rode enough to gain an appreciation of the 6R's ability to be placed accurately on the chosen line and its predictable nature when ridden with a bit of wheelspin (wheee!). At the end of the day, we returned to the Hotel and cleaned up for an oddly fish-centric dinner, punctuated with the rude comments and off-color jokes that can only be told by a bunch of drunk & jetlagged motojournalists.
I think I remember belching a tequila flavored prayer into my pillow before I lost conciousness.... It went something like this: "Please lord, let the track be clean and dry tomorrow, cause I think velocity is an excellent hangover cure."