Cycle News - Archive Issues - 2000's

terparts, and the lO-percent chance of rain the following day ended up being a bust. So, we headed to the Circuito de Almeria for a full day of track riding. The first couple of sessions were a bit on the damp side, but by lunch time the track had dried out completely. The Almeria track is a good test track because it offers a diversity of corners and plenty of stop-and-go sections, and the long back straight is perfect for feeling out the motor. Kawasaki went to great lengths to improve the power output from the ZX6R this year. The motor has been completely redesigned from the sump to the cylinder head. Starting at the top, the cylinder head features larger intake and exhaust valves, with different spacing for improved efficiency, combined with new cam profiles. Additionally, the intake ports have This top view not only shows how slim the new ZX·6R is, but it also shows the split fuel· tank/ airbox cowl. been polished to improve efficiency. The motor features a very compact, 25-degree included valve angle to improve the efficiency that the mixture gets into the combustion chamber. The pistons are brand new and feature reshaped crowns, in addition to shorter skirts for reduced friction. The crankshaft has been strengthened to reduce flex and features larger-diameter main journals, which were increased from 30 to 3 Imm. The engine cases themselves are now thicker castings to add rigidity and reduce vibration, and the oil sump is deeper to avoid oil starvation at extreme lean angles (or while doing wheelies). The oil pump itself is now wider and spins slower for improved flow. Feeding the fuel/air mixture to the engine are brand-new throttle bodies, which have 38mm, oval-shaped subthrottle valves and feature two injectors for each cylinder - one mounted in the standard position in the throttle body and one shower-type injector mounted in the airbox above. The oval shape of the throttle bodies has allowed airflow to be increased by 20 percent without making the throttle body assembly any wider. The secondary shower-type injectors in the airbox kick in once the motor reaches 5500 rpm. The RAM air system and airbox have been redesigned to feed the new throttle bodies more air. The tank shroud is now split, with half of it covering the fuel cell - which keeps most of its mass low down in the frame for a better center of gravity - and the other half covering the airbox. Another key to the ZX-6R's performance is the addition of an exhaust valve just up stream from the new, under- the-seat exhaust, which helps improve low- and mid-range performance. This is the first time Kawasaki has ever used this type of device on a 600, and it is actuated by the ECU depending on throttle position and engine rpm. The ZX-6R also features a catalytic converter for the first time this year, which resides underneath the engine and not up under the seat. This should keep the passenger seat cooler. I can assure you that these changes make a big difference from a performance standpoint. On the track, it was obvious that the ZX-6R meant business. On the long back straight the motor pulled incredibly hard for a bike just a tad larger than 600cc, but it's really amazing how much power that 36cc adds. Another area that really impressed me was that while exiting some of the tighter corners, I had to be fairly careful opening the throttle in a couple of places to keep the rear tire from spinning up, especially in the morning before the Bridgestone BT-002 race tires were fitted. This bike just plain hauls. One welcome addition to the bike for 2005 that was borrowed from the smaller displacement ZX-6RR is the ramp-style slipper clutch. At the end of the back straight, it's necessary to back shift three or four gears before a chicane. Even with the back tire barely touching the ground under hard braking, the rear end stayed inline. Feel from the slipper clutch was predictable and at times hardly noticeable at all. And while on the subject of braking, the front discs are new, 300mm petal-style units with four-pad, four-piston radialmount calipers taking care of the squeezing. Out back is a 220mm petal-style rotor with a single-piston caliper. I can't say enough about how well they worked on the track - both feel and power were difficult to find fault with. Perhaps the number-one reason that the ZX-6R lost our shootout last year was that the suspension on the bike was extremely harsh, especially on the street. Kawasaki has addressed this problem • head-on by not only changing the suspension both front and rear, but also by switching from Kayaba to Showa units. This came as somewhat of a surprise, but the engineer responsible for the change said that Kawasaki was willing to make whatever change was necessary to improve the suspension - and the Showa stuff was simply better. I didn't get that much time on the street to get a good feel for it, but it did feel a bit plusher. On the track, however, I thought that the suspension was a huge improvement. The 4 Imm inverted fork felt plush without blowing through its travel, and it offered plenty of feedback. The same can be said of the rear Showa shock, which felt like it was gliding over the undulations in the track instead of skipping over them. One of our complaints about the ZX-6R in the past has been that it just didn't turn as crisply as the R6 or GSX-R, but the new ZX-6R has a new frame and swingarm designed to remedy this. The frame is now roughly 13mm shorter from the steering head to the swingarm pivot, which allows for a longer, GP-style braced swingarm, giving the bike stability and the ability to hook up coming off of the corner while still allowing the bike to turn qUicker. The wheels are all-new, ZX-IOR style, sixspoke units that are lighter for reduced unsprung mass, in addition to the lighter petal-style brake rotors. So does it turn any better? Certainly especially through Almeria's three fast chicanes and sole, ridiculously slow bus-stop chicane. The ZX-6R - without riding it back to back with the competition - feels a lot more CYCLE NEWS • JANUARY 12,2005 21

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