2013 Kawasaki Ninja ZX-6R (636) Test
Whether or not the long-stroke 636cc 2013 Kawasaki Ninja ZX-6R is a cheater bike or not is beside the point. Few motorcycles are ever ridden in anger, as the majority of riding is done on the canyons and non-competitive track days. It’s all about besting your friends and talking trash after the ride is done.
Outside of the increase in displacement, the new ZX-6R gets a full complement of modern electronic enhancements, as well as improved suspension, braking, steering, clutching, and bodywork. Considering the flaccid sales in the supersport market, Kawasaki’s dedication to the segment is laudable, and may be what is needed to perk up interest in the mid-size class.
Track time was essential to evaluating the 636, and Thunderhill Raceway Park in Willows, Calif. was a perfect location for the job. I raced at Thunderhill 10 years ago and was reminded why I had missed it so much. The track has almost every type of turn or section of turns a road course can offer. It is roughly three miles long and, even with a long front straightaway, you are not resting a single second.
Everyone will focus on the new motor, and with good reason. Where most 600s fall flat on power at high rpm, the 636 kept pulling all the way up to the stratospheric redline. The updates to the motor would fill a book, and it is not any single change that makes the difference.
No doubt, the larger intake and exhaust ports, longer duration and higher lift cam profile, larger airbox, new Keihin throttle bodies (with oval sub-throttles), and tube-balanced exhaust do much of the heavy lifting. Many of the other changes are durability enhancers, such as chromoly camshafts, updated pistons, stronger piston pins, plus connecting rods with thicker stems and larger-radius small ends. It will take a year of hard use to know the results, but Kawasaki has focused on both power and reliability.
Increased torque was a primary focus for Kawasaki engineers, as evidenced by the 37cc displacement increase coming from a longer stroke, rather than wider bores.
The result isn’t perfectly balanced, as the 636 pulls hard off the exit yet seems a little lackluster toward the end of the mid range power, before pulling hard again at the very top. I have to emphasize that it was only slightly noticeable and certainly not a deal-breaker, especially for those not pushing the motor to its absolute limit. Still, there is enough power that the Ninja 636 pulled a wheelie on upshifts, something I was not expecting on a stock 600.
The FCC (Fuji Chemical Company) clutch is new to the 636, though we have seen it on other Kawasaki sport bikes. It’s a clever design, with a cam that pulls the clutch hub and operating plate together, compressing the clutch plates under load. This allows a surer connection with lighter springs, keeping the pull light at the lever.
Downshifts are handled by a slipper cam that reduces the clamping force on the clutch hub and operating plate when dropping gears aggressively, preventing rear wheel hop on trailing-throttle.
Clutches are a big deal for me. I think I went through a number of transmissions in one season – riding every other weekend – on my 2003 Kawasaki race bike, so I was definitely looking forward to what the new 636 had on the track.
Rapid downshifts of up to three gears are necessary for T-Hill, and the FCC clutch and Kawasaki transmission handled these perfectly. I never even came close to a false neutral or missed-shift, each gear was solidly and fully engaged, super deliberate, all the time very quick. It is, hands down, the best clutch and transmission combo I have felt on a 600.
Imagine cresting over a blind hill in 4th or 5th gear. You cannot see where you are going, and once you come over the rise, you grab a handful of brake and make three downshifts.
After the initial bite from the brakes and first down shift – and coming downhill – the rear end gets light and slides just a little. However, once the slipper clutch is fully up to speed on what is happening, it keeps the momentum going forward. The next two downshifts occur with minimal rear end slide to the point of it being unnoticeable.
The other aspect of deceleration is, of course, the brakes themselves. The Ninja 636 gets new radial-mount monoblock Nissin calipers grabbing onto 310mm petal stainless steel rotors in the front. More importantly, the master cylinder is a radial pump design, which has a huge impact on at-lever feel. I adjusted the lever out, as I like it stiff so I don’t have to pull very hard on the lever. I like a lot of bite, and bite do they ever!
Just after pulling the brake lever, the initial bite is not dramatic yet the front end does dive slightly. Granted, this is a very plush dive into the more useable part of suspension, which contributes to the effortless turn-in effort required on the 636.
After learning the track and getting comfortable with the bike, I noticed that my brake markers were getting deeper each session. I was constantly surprised I had slowed down too much or too early for the approaching corner. Having confidence in your brakes is essential for a motorcyclist and even more crucial for a track day enthusiast and most definitely, a racer.
T-Hill has numerous rises where the front end gets light under hard acceleration; this is where the rear brake comes in very handy. Although some rear brakes have a bite almost as sharp as the front, I prefer to have minimal rear brake bite because I am almost always using it to keep the front end down over hills, and only occasionally do I use it entering turns. The 636 rear brake is casual, not abrupt – just how I like it.
With the motor and brakes sorted out, it was time to concentrate on the handling and suspension. As I slowly came up to speed my first session, it appeared as if I was finding every bump on the track. The front end felt very soft – too soft – to the point it was bouncing around on every bump I hit.
I was a bit surprised, as the Ninja 636 has the new Showa BP-SFF (Big Piston-Separate Function Fork), which has springs on both sides, with preload adjustability in the left tube exclusively and damping pistons and adjustability all in the right tube. With all the adjusters on top of the fork tubes, there is a temptation to start twiddling immediately.
Rather than make all sorts of adjustments, after a cold, slow session I decided to wait until the following sessions to see if further adjustments were necessary. At the end of the day, I had not made a single suspension change to the 636. I was shocked.
Kawasaki techs, who had their watchful eye on me, admitted they raised the rear ride height and stiffened up the damping before letting me out on the track. Still, this was the standard track day setting used‚Äînot even the sag was changed.
Of course, the Ninja could use some fine-tuning for the consistent track day rider or racer, but for your typical street or track day rider, you’re good to go with the standard track day settings.
Front end confidence is critical for initial corner turn-in. Most of the time, this happens at a very high rate of speed and the front end can feel a little unstable. Not the 636, however. It continuously and effortlessly handled these high-speed approaches (such as Turn 1) with complete stability.
Due credit has to go to the Bridgestone Battlax Racing R10 tires. These are not the flagship DOT tires for nothing. Feel and response is crucial, and the Bridgestones delivered without fail.
I found myself not using up the entire racetrack as the motorcycle held its line superbly. The initial bite of the brakes kept the front end low and I never experienced an abrupt rebound or pogo effect that would cause the Ninja 636 to run wide.
The handling is simply outstanding; I was highly satisfied with stability on turn-in, holding my desired line, and exiting the turn without running right up the end of the racetrack.
Further into setup, it was time to work with the Kawasaki Traction Control (KTRC) system. Similar to, but not the same as the Ninja ZX-10R and ZX-14R systems, there are three modes of traction control available, as well as the option to turn it off completely.
I was most comfortable with full power, Mode 1 (least regulated), which allows some spinning of the rear wheel. Exiting the corner hard on the throttle can be a little sketchy at Thunderhill with all the elevation changes, yet with Mode 1, the bike would experience a nice, smooth, controlled slide with no abrupt movements or changes.
Coming down the Corkscrew-like section, you’re in first gear at the top, clicking into 2nd while straight up and down, and then go to full lean dropping down in elevation significantly hard on the gas. Put simply, it is High Side City, and the only rear end sliding I experienced in this section was at the very exit of the turn once the track had already flattened out. I felt confident and was even surprised with how gracefully the 636 handled the section.
Mode 2 and 3 traction control (middle and highest regulated), combined with full power would be great for riding in the rain, or for a very inexperienced track day rider. Again the power curve was smooth and steady, electronics have changed the game!
The motor also has a Low power setting, which I knew would not be to my liking, though it may be in the rain. The low power setting is extreme, and the bike is begging to be unleashed. The regulation is smooth, there’s no abrupt revving, and the power curve is steady. I would use this setting to teach my Mum how to ride – maybe even grandma.
I did experience the motor with the KTRC traction control off on full power. The only time I really noticed the lack of traction control was at the exit of the turn when I rolled on the throttle hard, still holding significant lean angle. Mode 1 had exactly the right amount of impact, and remained my preferred setting. Kawasaki got the traction control down on this bike just as the Ninja ZX-10R; it is flawless.
The Ninja 636 does have lights and mirrors, so a bit of time on the street is an essential part of the test. The racing position necessary for the track does not sacrifice comfort for the street, and I wasn’t the least bit sore after close to 100 miles.
Everything I liked on the track was reproduced on the road. I noticed how light the steering felt, which is a positive for street riding. The suspension had been adjusted to be street-friendly after the track time, and that was a plus.
I hopped on my older competitive-brand supersport bike the day I came home and the first thing I noticed was how heavy and sluggish the front end felt in comparison to the 636.
When a bike gets a wholesale update as the Ninja ZX-6R did this year, there is no way to predict the outcome. Yes, you expect improvements as technology refines the riding experience, yet you are still at the mercy of engineers, developers, and budgetary constraints.
Given that, the 2013 Kawasaki Ninja ZX-6R is an unqualified success. The larger motor is only part of a brilliantly painted picture. With all the upgrades working in concert, the only limitation you have on the track is yourself.
Photography by Adam Campbell & Kevin Wing