Of all the classes and categories that exist in motorcycling, none is as hotly contested among manufacturers as that of the supersports. Middleweight sportbikes represent the cornerstone of street-going product in the United States, with bragging rights and consumer demand driven directly by success on the racetrack.
Winning an American Motorcyclist Association (AMA) Supersport Championship is a coveted and essential element to earning a piece of this all-important market share. As a result, the title chase has become a gloves-off affair to create the best production-based 600cc sport machine. The clear winner in this annual gambit is the consumer, benefiting from the mercurial technological and engineering advancements that drive motorcycle manufacturers to win.
Kawasaki currently holds the AMA Supersport Championship title (as well as the runner-up position) with its supreme ZX-6RR 599cc machine. In addition to the one-two punch on the track, Kawasaki—clearly marking its intentions to own the middleweight class—offers consumers an incremental edge over the competition with the ZX-6R 636. The addition of those 37cc, combined with 20 years of Ninja pedigree, have made the ZX-6R Kawasaki’s best-selling motorcycle.
Like its racing sibling, the ZX-6R is clearly aimed at hardcore sport riders, while providing a more user-friendly street machine with the added bump in engine displacement and a wider-ratio transmission. The machine radiates confidence with striking good looks—born from the aerodynamic sensibilities of the wind tunnel—and extraordinary performance which come together to deliver a visceral wallop that is impossible to dispute.
To allow the ZX-6R a proper forum to divulge its racing roots, we spent two full days as guests of Takeit2thetrack.net, screaming the machine around Spring Mountain Motorsports Ranch in Pahrump, Nev. Delivering crisp yet smooth throttle response, the in-line 4-cylinder engine performed extremely well at low rpm—where its ample torque impresses for a supersport—but it prefers to be wrung out and really starts to sing at the higher rev range, coming into its own well above 11,000 rpm. (Click images to enlarge)
Dual-stage fuel injection smoothes out the all-too-familiar hiccup encountered when rolling the throttle on from the fully closed position, and helps take the jerkiness out of getting back on the gas mid-corner. This makes negotiating a series of turns, which requires continual on-and-off throttle action—especially at lower speeds—a much easier experience that should not be underestimated by the track day novice and which will be equally appreciated by experts.
Inverted 41mm, fully adjustable Showa forks and Kawasaki’s patented Uni-Trak rear shock linkage absorb the potholes and uneven pavement of real world street riding as well as provide top level performance for track day outings. A dry weight of 362 pounds, combined with a short wheelbase and a long, braced swingarm (a design borrowed directly from Kawasaki’s GP bikes), results in nimble handling. Whether under hard acceleration or during seriously aggressive braking, the machine stays composed, without any twitching or chatter from either the front or rear end. The ZX-6R is a solid, stable motorcycle.
The dual 300mm front brake discs—as well as the single rear 220mm unit—have a petal-shaped perimeter that adds not just a styling cue taken directly from the race bike: The front 4-piston calipers are radial-mounted for positive, incremental feel at the extremely high braking forces encountered at racing speeds, yet they also deliver smooth, confident braking for everyday street riding.
The 6-speed transmission has been refined and no longer has the disconcerting clunk that previously haunted shifts between first and second gear. In equal measure, the new gearbox allows the rider to find neutral with ease—something the previous year’s models had difficulty with. The ZX-6R comes standard with an impressive race-inspired slipper-clutch. This back torque–limiting unit allows aggressive downshifts by automatically synchronizing rear wheel speed to engine rpm for smooth, progressive shifts while reducing the possibility of rear wheel hop or lockup.
The cockpit of the ZX-6R takes its dimensions and ergonomic feel from its big brother, the ZX-10R, accommodating taller riders with a more spacious seat/handlebar/footpeg relationship. The steering head has been pulled back, reducing the rider’s reach to the handlebars, rendering a seating position that allows for more precise leverage and control. The Kawasaki utilizes a dashboard instrumentation layout that combines a digital speedometer, LCD tachometer, temperature gauge, clock and trip meter into a very compact unit tucked between the windscreen and top triple clamp. Overall instrument visibility for the rider is quite good, but readings on the LCD tachometer are difficult to discern in bright sunlight. (Click image to enlarge)
The ZX-6R is a comfortable mount with a healthy powerplant, whch makes for enjoyable street and canyon outings. But as proof of its embedded racing DNA and Kawasaki’s clear intention for its use as a track day machine, the 636 comes with an adjustable shift indicator and lap timer.
The shift indicator is easily visible in the lower peripheral vision, which helps the rider keep his eyes on the track, rather than counting revs on the tachometer at race speeds. The thumb-operated lap timer is an entertaining accessory, allowing you to monitor your progress on a circuit or, perhaps inadvertently, merely serving to humble you. Either way, with the ZX-6R beneath you, rest assured the ride is going to be very illuminating.