The ZX-6R’s new 636cc engine dishes up good stuff on the dyno, with power curves that follow a steeper, smoother trajectory than the previous 599cc version. Power falls off fast after 13,300 rpm, so short-shift to stay in the thick of it.
The 2013 Kawasaki Ninja ZX-6R 636 has the same ergonomic measurements as the 2009-2012 bike. Soft, well-damped suspension goes a long way toward making this sportbike tolerable for longer rides, while a reasonable rider triangle keeps you from feeling cramped.
Much More Than “Bold New Graphics”
The 2012 Ninja’s frame worked so well—with a great balance of longitudinal stiffness and lateral flex—that Kawasaki saw no need to change it for 2013. The only differences are new mounting points for the updated fairing. As on the previous Ninja, the 2013 bike debuts a new fork design. Both legs of the Showa Separate Function Fork Big Piston (SFF-BP) contain springs, but preload is set solely via the left leg, while the damping circuitry is relegated to the right leg. The Big Piston design provides superior damping at the beginning of the stroke, while the Separate Function format simplifies tuning and saves a claimed 220 grams. A revised shock has a softer, longer spring with more progressive linkage for a smoother ride on the street. The Showa shock is fully adjustable, but doesn’t have separate high- and low-speed compression tuning as on the previous model. Sliding the fork 2mm up in the new triple clamp reduces front ride height, while the longer shock jacks up the rear. Rake decreases from 24° to 23.5°, with sharper handing as a result. In an effort to lighten steering feel, Kawasaki removed the 2012 bike’s Öhlins steering damper and installed new, low-friction steering-head bearing seals.
By far the biggest news with the new Ninja is its return to a 636cc engine, but that’s just the start. In addition, all the engine’s ancillary systems were tuned to support the displacement bump. The extra 37cc is achieved via a stroke increase of 2.6mm, for bore and stroke measurements of 67mm by 45.1mm. The engine uses shorter, stronger conrods to accommodate a longer crank throw, and the pistons’ longer travel necessitated lowering the cylinder ports, which are in place to reduce pumping losses at high rpm. The camshafts were tuned to suit the stroke increase, with longer intake duration and a 0.2mm increase in intake- and exhaust-valve lift. The piston crowns were reshaped to make room for the valves’ increased movement and to reduce compression slightly, which goes from 13.1:1 to 12.9:1. The 2013 Ninja ZX-6R now has an “assist and slipper” clutch, which uses a pair of cams to provide more positive engagement while accelerating, and controlled slip when downshifting. The design transfers load from the clutch hub and basket to the cams, allowing Kawasaki to make the inner hub out of aluminum instead of steel, and to reduce the number of clutch springs from six to three, for a total weight savings of 700g and a much lighter clutch lever pull. Throttle-body diameter remains the same at 38mm, but the 2012 bike’s upper injectors were ditched in favor of larger, single, lower injectors. Deleting the upper nozzles allowed Kawasaki to increase the airbox volume by 11 percent, smoothing power delivery and boosting peak output. The move also made room for longer velocity stacks, which help with low-end performance. Most of what resides between the crankcases is the same as before, but first gear is shorter and all the cogs are thicker for increased durability. The retuned exhaust has balance pipes across all four headers, while a reshaped sub-chamber houses a shorter catalytic convertor. The new bike has a narrower yet longer muffler, made from steel rather than titanium as on the previous model. Redline was lowered from 16,500 to 16,000 rpm. The engine’s measured output is 112 bhp at 13,300 rpm, and 46.4 lb.-ft. of torque at 11,300 rpm.
The 2013 Kawasaki ZX-6R raises the stakes in the middleweight class by offering comprehensive electronic rider aids. A hybrid traction-control package combines two sport settings culled from the ZX-10R’s Sport Kawasaki Traction Control (S-KTRC) with a third, stability-oriented setting from the Concours’ KTRC. Level 1 and 2 are meant to optimize acceleration and control tire spin and torque via ignition timing, while Level 3 combines ignition, fuel, and secondary throttle butterfly manipulation to totally eliminate any front/rear wheel speed differential in order to maintain perfect stability. Additional hardware includes front and rear sensors and associated wiring, but all the software magic is added to the existing ECU. The 6R also has two power modes: Full power is self explanatory, while Low maintains low-end and midrange performance but reduces peak output by 20 percent as well as softening throttle response. Other electronic updates include a new “Zero-Cross Control Voltage Regulator,” which provides more consistent voltage to the bike’s various electronic components and reduces electronic “noise,” enabling more efficient operation and also meeting new European regulations. The optional Kawasaki Intelligent Braking System (KIBS) uses the same sensors as KTRC, plus a Nissin ABS unit that contains its own ECU.
WHEELS & BRAKES
The Ninja rolls on essentially the same six-spoke cast-aluminum wheels as before, albeit with a revised front hub to suit the new rotors and no green rim stripes. The wheels are shod with Bridgestone’s new S20 hypersport tires, the successor to the BT-016s. The OE “J-spec” tires are different from standard S20s in terms of dimensions, and they’re also slightly lighter. The Ninja’s front petal rotors have grown 10mm, from 300mm to 310mm, to provide more stopping leverage. The rotors are also thinner (5mm instead of 6mm) to maintain the same weight as the 300mm discs. New, one-piece “monoblock” front calipers are more rigid than the previous two-piece units, and house four 32mm pistons each rather than a combination of 32mm and 30mm slides. The brake pad compound has been updated as well. At the rear, there’s a smaller Nissin caliper with a single 30mm piston—the same setup as on the ZX-10R. KIBS is a $1000 option.
Why commit to a thorough mechanical and electronic update only to hide them under last year’s clothes? Kawasaki didn’t, so the 636 gets a nose-to-tail styling update. Up front, a larger intake duct fills the gap between the new projector-beam headlights, while new mirrors like those on the Ninja 300 project from a more slanted front fairing section that’s said to have less drag and provide better wind protection for the rider’s hands and shoulders. New integrated front turn signals preserve the Ninja’s racey lines, while new body panels extend from the headstock on back to the tail, covering the upper frame spars in painted plastic. On the previous model you could see a radiator hose peaking through the fairing in front of the cylinder bank, but that’s been addressed via revised routing that keeps the hose hidden. The previously-mentioned muffler is attractive enough to avoid being immediately replaced by an aftermarket part, and the tail section now houses an LED taillight.