Kawasaki's Kenan Sufuoglu won four World Supersport races in 2012 and finished the season atop the points standings. This in itself is hardly news, as Sufuoglu and Kawasaki have separately proven strong contenders in any series. What's interesting though is that Sufuoglu's success last year came on a bike that Team Green will not ship to the U.S. in 2013 — the 600cc ZX-6R, which will be offered overseas as a 2013 model. The U.S. market instead gets access to Kawasaki's new 636cc ZX-6R, a bike that the manufacturer has built with the everyday rider in mind.
Sport Rider is no stranger to the new ZX-6R platform; we first threw a leg over the 2013 model during the bike's world launch last October, and then touched on its many new features in our first ride report ("Born Again," January '13). Once the dust settled on the ZX-6R's big intro, however, we found ourselves still curious as to how the bike would handle daily commutes, and how it would work on roads that weren't bowling-alley smooth. On top of that, we wondered how the street-biased 636 would work at the track when there wasn't a flock of Kawasaki technicians attending to every last detail, including suspension setup. All of these were questions that warranted some more one-on-one time with the bike.
Our interest in spending added time with the new ZX-6R was coupled by a desire to expose the bigger differences between the 2013 model and last year's 599cc model. Aspirations in mind, we decided to throw a leg over not one, but two ZX-6Rs as part of this test; every inch of tarmac that we'd cover on the 636, we'd cover on its smaller-displacement sibling. This wasn't a chance to pick a winner between the two bikes, mind you, rather an opportunity to see if Kawasaki's change in pace had legitimately sent the manufacturer in the right direction. And if it had, how far had Kawasaki propelled itself into the green?
Don't judge a book by...well you know the rest
Kawasaki is quick to remind the industry that its 2013 ZX-6R is centered on around-town comfort, but its spec sheet suggests that the bike will still ignite your senses by way of clear-cut performance. The suspension, brakes and engine have all been updated, for instance, and Kawasaki's only sweetened the pot by outfitting the 636 with its three-level traction control system and separate power modes.
The ZX-6R's engine is the most reworked and benefits from a 2.6mm-longer stroke in addition to a slew of internal changes, including reshaped ports, cams and pistons. The 636 pumped out 111.2 horsepower at 13,300 rpm and 46.3 foot-pounds of torque at 10,900 rpm when strapped to our SuperFlow dyno. Our 2012 test mule, by comparison, spun the drum to the tune of 110.4 horsepower at 14,000 rpm and 44.5 foot-pounds of torque at 11,400 rpm. What's more impressive than the incrementally higher peak power figures is that the 636 holds its advantage across the entire rev range, and that the biggest gains are found between 7000 rpm and 11,500 rpm, precisely where you'll find the tach needle when riding at a safe and legal speed.
Roll-on testing further confirmed the ZX-6R's midrange advantage; the 2013 ZX-6R went from 60-80 mph in just 3.13 seconds and 80-100 mph in 2.91 seconds. Compare that to our 2012 test model, which covered the former gap in 3.64 seconds and the latter in an elongated 3.49 seconds.
The 2013 ZX-6R's ergonomics remain track-focused, but a relaxed reach to properly positioned clip-ons means 60-mile-plus commutes aren't succeeded by ten minutes of "ice on, ice off" wrist therapy. That same level of comfort doesn't trickle down through the rider triangle, and we found the footrest-to-seat distance to be insufficient for any rider over the six-foot mark. Fortunately, a slightly cramped seating position is among the only downfalls to the Ninja's otherwise stellar ergonomics package. Typical Kawasaki mirrors provide a clear, unimpeded view of who's in tow.
The newer ZX-6R's aggressively shaped fairings further blur your understanding of the bike's design brief, but a few miles spent in the saddle remind you of its street-biased nature. Biggest difference this year is that both the clutch and brake lever have a lighter pull and consequently require less forearm manipulation. Feel through the clutch lever's travel is silky smooth as well, which works in conjunction with the torque-happy engine to provide effortless stoplight-to-stoplight launches.
The 2013 model's suspension package is developed around .50N/mm lighter fork springs and a 7.5N/mm lighter shock spring that further boost around-town performance. The setup absorbs potholes, manholes and speed bumps with a plushness that would otherwise have had us believing the 2012 bike was suspended by wood slats. The benefits don't culminate at the freeway onramp either; the newer ZX-6R coasts down the interstate with few wrinkles in the chassis and absolutely no buzz through the handlebar. Frankly, our test riders could only wish to have had the same comments regarding the 2012 ZX-6R.
The 636cc ZX-6R’s primary...
The 636cc ZX-6R’s primary advantage is from 7000 rpm to 11,500 rpm, which is precisely where the tach needle rests when riding down the freeway or at city street speeds. Something tells us that’s hardly a coincidence.
The 636 engine is no powerhouse up top and starts gasping for air well before you run into the rev limiter, but that increase in midrange power that was highlighted by our back-to-back dyno runs proved advantageous through every last section of canyon road that we covered. Last year's ZX-6R isn't a poor performer through any part of the rev range mind you, but the 599cc engine shines brighter once the tach needle skips past the 13,000 rpm mark — pass that point on the street, however, and chances are you'll almost immediately be seeing flashing red/blue lights in your mirrors. The 636, in comparison, happily grunts off the corner almost regardless of where the needle resides, and continues to drive through the midrange in a way that allows you to forgo the shift lever in the tight stuff.
The 2013 model's modestly damped Showa Separate Function Big Piston fork and rear shock surprisingly don't reach their limits any quicker than an experienced rider would, and provide such a high level of feedback that they were extremely easy to set up at the track — even without Kawi techs on hand, mind you. The 636's 5mm-shorter wheelbase combines with a .5-degree steeper rake to make the bike much lighter through a right-left transition, and the only area where the newer ZX-6R steers slower is at the entrance of the corner. Presumably, the latter characteristic is a result the bike being buried in the lower part of its travel as a result of the softer, aforementioned springs.
Corner entrances aren't by any means a tiresome experience on the 636, and the F.C.C. clutch manages to keep the bike stable under aggressive braking. "The slipper clutch works really well," claims Kento, who goes on to say that, "I think Kawasaki's done a good job of tuning the fuel injection under deceleration, which helps as well." The Nissin brakes deserve equal praise, and are far superior to the two-piece units on the 2012 model. Biggest difference is that the monobloc pieces have a less aggressive initial bite, but plenty of power through the pull. Last year's calipers, in contrast, are much more difficult to modulate and are just a finger twitch away from upsetting the chassis. Even at a tight track like the Streets of Willow, there was absolutely zero brake fade to speak of when riding the 2013 model.
The 600's engine initially feels stronger at the racetrack (and its top-end performance would likely hold benefits on a track with longer straights), but it becomes readily apparent that the more lively sensation is a result of its more aggressive power delivery than an actual power advantage. The 636 feels less frantic on the gas; it's a little like a matured honor-roll student in comparison to the ADD-distressed teenager that the 2012 bike resembles. What's more, the 636's added midrange allows you to drive through the middle of the corner without wrapping the throttle to the stop (in search of revs) and testing adhesion limits.