Kawasaki did the modifications to its ZX-6R in house, using a majority of parts which are available from their performance parts catalog.
MotoUSA’s reigning Supersport Shootout champion comes into this comparison as the odds-on favorite. With no changes for ’10 with the exception of the BNG (Bold New Graphics) treatment (you had to know that was coming somewhere in this story…), the Kawasaki started with a target on its back, and for good reason. Not only does it make the most power out of the box, but it was also quickest in our ’09 Superpole session and picked almost unanimously by all testers in last year’s comparison. With ex-factory racing mechanic Joey Lombardo building the modified ZX-6R in house at Kawi, we suspected big things would be the result. Were they ever…
For Stage 1 Team Green aimed to source the majority of the go-fast parts from in the Kawasaki Performance Parts catalog. They opted for a Leo Vince SBK Corsa titanium full exhaust with titanium and carbon end can, while a Kawasaki kit adjustable ECU and wiring harness adapter where put in place and tuned to match the exhaust. As for gearing, the ZX-6R comes from the factory with a 520 chain. All Lombardo had to do was get new sprockets, those coming from
Drive Systems USA, the chain remained stock. With the quick addition of a shim on the rear shock to add more forward weight to the ZX and mirrors removed the Stage 1 changes were complete.
If the dyno made one thing clear it was that once derestricted the Kawasaki makes some serious power. While all three of the others where within 1-2 hp, the ZX topped the entire field by more than 5 horsepower, turning the drum to the tune of 117.94 hp – a jump of over 12 hp from the 105.87 it made in stock trim. This gain was second only to the Honda in terms of improvement, as the CBR600RR gained just over 13 hp from stock. As for torque, this was much more in line with the competition. The ZX was just shy of the class-leading Suzuki in modified form at 45.97 lb-ft compared to 46.30 lb-ft, respectively, picking up a little more than three lb-ft over the 42.75 it produced in stock trim. In fact, all four 600s were extremely close in this regard, a range of only 1.06 lb-ft separating the entire field once modified.
The ZX comes into this shootout as one of the heavier stock machines, weighing in at 422 lbs full of fuel. Removing the stock exhaust helped out its cause, shedding 15 lbs in the process. Combined with the slightly lighter sprockets the end result was a ready-to-ride wet weight of 405 lbs, which was the heaviest of the bunch by a single pound over the Suzuki.
With the addition of a Leo Vince exhaust and Kawasaki’s kit ECU, the ZX-6R was easily the undisputed horsepower king in Stage 1, pumping out 117.94 hp and 45.97 lb-ft of torque. Sprockets were sourced from Drive Systems USA.
As expected the Kawasaki’s engine was smack-you-in-the-face apparent from the first lap out of the pits. Strong throughout the rev range, once above 12 grand the beast came to life and left everything else floundering in its wake. Also the addition of the Kawasaki kit ECU gave an additional 1500 rpm of over-rev up top, extending redline from 14,000 to 15,500, something that didn’t go unnoticed. And the ZX would pull all the way to the limiter with no signs of letting off. Compared to stock the horsepower also peaks a full 2000 rpm higher, the base bike topping out at 12,200 rpm while the Stage 1 machine peaks at 14,200 rpm. Though while the engine was no question the ZX’s crowning glory, it also caused the bike’s low point during the second day of the test, which we will get to shortly. First let’s touch on the good stuff.
“The Kawasaki has hands down the strongest motor,” Sorensen remarks. “It has all the low-end power that you would want in addition to having a strong upper-mid range and the most over-rev of any of the bikes. The power has more noticeable steps than some of the other bikes, but feels like there is more acceleration, so it’s worth it.”
Neuer’s comments reflected those of Chuck’s. “The Kawi was super strong all the way through the power curve and the map was spot on,” he adds. “It’s just plain fast, making strong and usable power from top to bottom. It’s also not only the fastest but also one of the most forgiving if you make a mistake and lose revs.”
The Kawasaki is without question king of the motor wars, but as I alluded to earlier it showed some signs of weakness on Day 2 of the shootout. During our Superpole session on Sorensen’s out-lap, already nearly at full-tilt, wide-open down the back straight, the engine completely let go, seizing a rod bearing and blowing a hole through the case the size of my fist (that’s not an exaggeration in any way). Thankfully Chuckie was on the ball and as soon as he felt a vibration pulled in the clutch.
Despite it dumping out every last drop of oil instantaneously, much of it on the rear tire, Sorensen pulled off the save of the century and didn’t go down (he’s a former AMA champ for a reason). He then pushed the bike back to the pits and as the track was cleaned Lombardo, along with help from the Suzuki and Yamaha boys, was able to get the parts switched to the back-up bike and still made it in Superpole. Amazing stuff.
Yamaha and Suzuki both chipped in right away to aid Kawasaki in getting the back-up bike ready for Superpole after the original blew a hole in the case halfway through Day 2 at Streets of Willow.
Though the question quickly arose: How could a fairly stock bike with limited modifications have such an issue? Was it the additional rpms allowed by the kit ECU? Following the shootout Kawasaki went back over the damage and claims this was from a case (or cases) of mechanical over-rev, which happens most of the time when a rider downshifts improperly, pushing the motor past redline under deceleration, something the rev-limiter is unable to stop. Kawi believes this may have happened earlier in the test at some point(s) and weakened the engine in several areas as a result, adding that it had nothing to do with the additional rpms allowed by the kit ECU.
Whether or not this is the cause we have no way of knowing for sure. One thing worth taking into consideration in Kawasaki’s defense is that the horsepower and torque numbers you see here are from the back-up bike, as the dyno runs were performed following the track portion of the shootout. This shows that any new 2010 Kawasaki ZX-6R would more than likely be capable of these horsepower gains, and that the engine’s malfunction may have merely been a fluke. But we will let you be the judge.
One thing that was for sure was the Kawasaki’s well-sorted final-drive gearing. The 15/45 combination worked extremely efficiently at both tracks, providing good drives off the slower corners at Streets and easily pulling top gear down both the back and front straights at Big Willow. Much like the Honda, the ZX’s gearing was head and shoulders above the other two without making a single change at either track.
“Both the Kawasaki and the Honda were geared exactly where they needed to be,” says Sorensen. “The Yamaha and the Suzuki both ran five-speeds at the big track whereas the CBR and ZX would pull top gear without problem. Same held true for streets, as the ZX worked well everywhere and wasn’t between gears at all.”
Showa’s Big Piston Fork on the front of the Kawasaki continued to receive praise on corner entry and mid-corner, though the bike’s limiting factor is without question the stock shock.
Handling was a much improved area over its ’08 predecessor, thanks to the addition of Showa’s Big Piston Fork. This aided in corner entry and handling overall, though the ZX’s stock rear shock has always been a point of contention and weakness for the green machine – and the current bike is no exception. While one can push extremely hard going on the brakes, mid-corner and exit is limited by the rear end as one can only tune it to a certain extent without hampering the bikes abilities in other areas, making for a constant compromise, more so than some of the competition.
“I give the Kawi fork a high rating not just because of the feedback you get from it but also for the excellent adjustability you have in the settings, and that you can notice the differences when you change the clickers even the smallest amount,” says Sorensen. “Kawi used higher quality internals for this fork and it shows. Eventually the other manufacturers will apply the same thinking.”
As for the shock, Sorensen adds: “The rear moved around a bit more than some of the other bikes and was one of the limiting factors for the Kawasaki.” Neuer was on the same page, commenting that the “shock need a bit more preload or something, it was sketchy at the big track; lots of movement in Turn 5.”
With the exception of its strange engine issue on Day 2 of the comparison, so far the Kawasaki (above) and Honda have stood out as the front running pair so far.
Even without being able to get the shock perfectly set up, at Big Willow where motor is king, the Kawasaki came out on top with a best time of 1:27.36, four tenths ahead of the second-place Honda, which did a 1:27.75. As for Streets, the top two switched spots, with the Honda taking honors in front of the Kawi, 1:19.27 to 1:19.56, respectively. Averaging the two shows the Kawasaki just edges the Honda overall, though by less than a tenth of a second. Also consider that the bike which was ridden in Superpole at Streets was the back-up bike due to the first blowing up, on which no previous set-up had been done.
In regards to how it compares to last year in stock form the Kawasaki made one of the smallest gains in terms of outright lap times at Streets, dropping from a 1:20.23 (which was the fastest of the ‘09 test) to said 1:19.56, a gain of just under seven tenths of a second. This is still a formidable gain, however, especially considering how good the bike is in stock from. It did win last year’s shootout.
While this is only the first stage of our Modified Supersport Shootout and we won’t be determining a winner until all is said and done, one thing has become extremely clear – the more modifications we add the closer these bikes get. With the exception of the Kawi’s hp numbers, all the bikes spun the dyno within a couple hp. On track things were even closer, as the gap in lap times at Big Willow was just over seven tenths of a second and at Streets it was a hair over one second. This compares to a gap of almost 1.8 seconds at Streets during the stock shootout last year.
From here the bikes get upgrades to the suspension and brakes, plus a speed shifter, rear-sets and clip-ons, turning each of them into full-fledged trackday weapons. The Kawasaki and Honda proved strong so far but will the addition of more mods help put the Suzuki and Yamaha pull back into contention? Or will the gap get even larger? Stay tuned for Stage 2 to find out.