When we pitted the updated ZX-9R against the CBR929RR and latest R1 (August 2000), the Kawasaki--facing competition with near-seamless carburetion and fuel injection--was hampered by its abrupt throttle response. Specifically, when the Kawasaki's throttle is opened on corner exits, no matter how smoothly, the engine catches suddenly after a moment's hesitation, causing some instability and making the bike run wide. This isn't very much fun when running too wide means a 100-foot drop into a canyon. This characteristic tarnishes an otherwise excellent motorcycle, which garnered high marks in our open-class comparison test for ergonomics and general everyday use.
Raising the needles slightly (something that works wonders on '98 and '99 ZX-9Rs) and messing with the fuel screws on our test bike's carburetors failed to remedy the situation, so we turned to Factory Pro's Marc Salvisberg (800/869-0497) for his take on the ZX-9R. According to Salvisberg, the bike's Keihin CV carb design is shared with one other bike--Yamaha's R6, which suffers from the same malady to a certain extent. But because the R6 is much less powerful, the symptoms are less noticeable. Salvisberg says the culprit is the emulsion tube (the brass nozzle the needle slides into and what the main jet attaches to), and new emulsion tubes are the key component in Factory's ZX-9R jet kit.
We installed said jet kit in our test bike, along with a BMC air filter and a Leo Vinci (877/463-4462) full exhaust system, with excellent results. Immediately, we noticed the surging above 6000 rpm had disappeared; the engine picks up cleanly during off-on throttle transitions. And not only is peak power up a bunch, but also the 9's already stomping midrange is boosted significantly. The recommended settings from Factory Pro give the bike amazing pull from lower rpm--enough to lift the wheel from as low as 4000 rpm in first! We found the jetting to be a tad lean in the 4500 to 5500 rpm range, with some of the old stumble present, which was remedied by raising the needles a notch, but the trade-off was some power just off idle. If we had more time to play with the Kawasaki, we'd try some needles with a bit less taper.
A phone call to Targa Accessories (800/521-7945) netted us some bits and pieces to dress up the ZX-9R. The seat cowling, frame sliders and smoked windscreen give the bike a purposeful look, and the aluminum footpegs are much grippier and give better feel than the stock rubber-covered parts. This was also a perfect opportunity to try Bridgestone's new BT010 tires (800/543-7522), which are standard equipment on ZX-9s sold overseas.
Our bike shed some weight (approximately seven pounds) with the switch in exhaust systems, and the high-quality Leo Vinci pipe is quite mellow around town and at lower revs. Sound levels increase as the revs are dialed-in, with the pipe measuring 101 decibels on our sound meter. Happily, the ZX-9 lost none of its around-town or highway manners, and is quite docile when discretion is used. In all, our experiment resulted in a better ZX-9R in virtually every way--more power, easier to ride and heaps of fun. --A.T.