2005 Kawasaki ZX-6R

story by Sean Alexander, Photograph by Kawasaki, Created Mar. 19, 2004
Almeria Spain, 12/15/2004 ~ 2005 marks the 20th anniversary of the GPZ 600R Ninja and the birth of the 600 Supersport class. Since that fateful day twenty years ago, the 600 class has been defined by constant improvement and a controversial trend towards narrow focused racetrack oriented sportbikes.

In 2003, Kawasaki fired one of the loudest shots in the 600 class, when it introduced the extremely aggressive ZX-6RR and 636cc ZX-6R. That ZX-6R made 108Hp at the tire, shading its competition by over 4Hp and scaring its riders with a razor sharp focus that translates into a nervous front end and a punishing ride on anything but the smoothest pavement. Still, its sizable horsepower advantage allowed it considerable sales success.

Twenty years of middleweight Ninjas

Not content with dominating the horsepower wars, Kawasaki has decided to refine the 6R's street manners, in an effort to challenge the more comfortable Yamaha R6 for top Supersport "Streetbike" honors. Because Kawasaki claims that the ZX-6R is aimed at street and track day riders, while the ZX-6RR is a limited production motorcycle aimed squarely at roadracers, the all-new 2005 ZX-6R receives special revisions aimed at improving its comfort and overall suitability as a streetbike.

Most notably, these revisions include a more linear powerband, flatter and more comfortable rider's seat, a slight relaxing of the old 6R's nervous steering geometry and an under tail exhaust. In addition, Kawasaki switched from Kayaba to Showa suspension components, softening the old 6R's (overly harsh) dampening in the process.

They also relaxed the riding position, changed the wheels to a lighter and stronger 6-spoke design like the ones on the ZX-10R, changed the brake rotors to a "petal" design (also like the ZX-10R), upgraded the master cylinder to a radial-pump unit, completely redesigned the frame, bodywork, intake and about twenty other things and generally refined the old bike into a nicer package. Kawasaki claims that these changes add around +3Lbs to the bike. Oh yeah, lest you think the ZX-6R is growing "soft" on us, consider this amazing fact: Kawasaki also redesigned the engine and they now claim that the 2005 ZX-6R has gained Nine horsepower.

The Rain in Spain....

"The 2005 bike should be putting something in the neighborhood of 117Hp to the ground!"

Since the previous generation ZX-6R made an honest 108Hp at the tire, the 2005 bike should be putting something in the neighborhood of 117Hp to the ground! Folks, I don't care if the thing has ape hangers and foreward controls, if it weighs less than 420Lbs wet and generates 117Hp, nobody is going to call it "soft".

Now that horsepower cat is out of the bag, let's discuss how Kawasaki achieved this stunning output from a mere 636cc of displacement. The obvious changes are the typical hot rodder tricks of higher compression and better breathing. To be specific, the 6R's intake throats have developed an oval cross section, allowing the total volume of airflow to increase, without increasing the actual diameter of the throttle bodies.

This prevented any frame widening to accommodate a wider throttle body rack. Immediately upstream of that rack sits a quartet of new "shower" type injectors, which come on-line above 5,500RPM to supplement the flow from the standard injectors. Once the mixture is properly enrichened, it enters a new cylinder head, which has been enhanced with a smoother surface treatment.

A quartet of new "shower" type injectors sit immediately upstream from the new oval-shaped intake throats.

Those smoother intake passages lead to a set of +1mm larger intake valves and once inside the combustion chamber, the mixture is compressed 12.9:1 (up from 12.8:1) by a new set of deeply crowned pistons with low-friction skirts, before igniting and being expelled through a set of +1mm larger exhaust valves. After exiting the engine, the gasses travel to a catalytic converter and then out through a new flapper-valve equipped under-seat muffler.

That computer-controlled valve is closed until around 5,500RPM (depending on throttle opening, etc.), increasing backpressure and boosting low-mid RPM torque. Above 5,500RPM, the valve opens an additional passage through the muffler, to allow the deeper breathing necessary for good high-rpm performance. In a reversal of SOP, Kawasaki moved the cylinders into a more upright position, reducing their foreward-cant from 25° to 20°. Other engine revisions include the addition of a slipper clutch like the one on the ZX-6RR, and a deeper oil sump with a revised pump, to reduce crankshaft windage and cut parasitic drag.

Choose Your Color!

Day 1 - The Street

All that power is well and good on the racetrack, but on public roads, it's the powertrain's refinements and the integration of the whole package that impresses most.

Though it is a cold morning, there is no need to pull any "cold start" levers, because the '05 bikes now feature an auto fast-idle circuit in their ECU. This means the ZX-6R fires-up with a minimum of fuss and quickly adjusts its idle speed to suit the engine's temperature. The Spanish countryside received a pounding from Mother Nature in the days preceding our visit, so the roads are mostly filthy and wet. As I accelerate away from the racetrack and out into the foothills, the new 6R quickly has me relaxed, because the throttle is delivering exactly the level torque that I request, so traction management is a breeze and the wet roads quickly fade to the back of my mind.

This "Raw Titanium" color and the new "Magma Red" are quite nice in person.

Between the flapper valve and the addition of those shower injectors, Kawasaki has managed to flatten the torque curve, creating a nice and linear power delivery, that pulls very hard through the midrange and then screams into the stratosphere. The changes are quite noticeable, though not what you would call "dramatic", thanks to the linear manner in which the torque is metered out.

After a few corners, it is immediately apparent that the shift quality and drive lash have been improved upon over last year's model and the new slipper clutch works like a charm. I would rate the shift quality as outstanding, very smooth and with a minimum of lash, slop or pedal travel. Of course it's no VFR, but this is one highly refined supersport.

The day's street ride, has us following a pre-determined route to various photo points and I enjoy the scenic views, as I cruise along between 50-260Kmh, depending on surface conditions and weather or not there is another vehicle within three miles of me. Spain is different indeed. After a few photos, I need to make-up some time on the rest of the group, so I find myself hustling through a nice set of twisty pass roads, where the conditions vary from soaking wet to sunny and dry, depending on what side of the mountain you are on.

The new ZX-6R quickly has me relaxed, because the throttle is delivering exactly the level torque that I request, so traction management is a breeze and the wet roads quickly fade to the back of my mind.

"The stakes are high enough to make me a bit nervous.."

The stakes are high enough to make me a bit nervous, but the bike is happy to oblige whatever my ego or cowardice decide to dish-out. In these conditions, there are three things in particular that I appreciate about the '05 bike.

1.) The new Radial-Pump Master Cylinder offers very good feel and allows me to meter braking forces with the same accuracy that the fuel injection delivers acceleration.

2.) Kawasaki relaxed the steering geometry from 24.5° to 25° and extended the trail from 95mm to 104mm, so that the bike has less of a tendency to headshake over rough pavement, than last year's bike.

3.) When they switched from Kayaba to Showa suspension components, they specified softer damping for the forks and shock, so the ride is smoother and less prone to chatter.

Now that I've been in the saddle for a while, I'm starting to appreciate the flatter seat, and more relaxed riding position. Although the pegs are in the usual (high) place, I find that overall comfort is excellent for a supersport bike.

To be fair, I didn't spend any time droning down a freeway or trolling through traffic, so a thorough evaluation of the bike's comfort level will have to wait for a stateside test. However, I do think it's safe to say that the new ZX-6R is at least as comfortable as any other supersport that I've ridden.

600 Class "Streetbike" Score: A

On a wet racetrack, the ZX-6R's supple suspension, linear power delivery and predictable brakes kept the drama to a minimum.

After our street ride, we met back at the Circuito de Almeria, for a short (wet) track session. Since we didn't have any full-wet race tires, conditions dictated that we keep the speeds moderate. Once again, the supple suspension, linear power delivery and predictable brakes kept the drama to a minimum.

Though we didn't really do much hot lapping, I rode enough to gain an appreciation of the 6R's ability to be placed accurately on the chosen line and its predictable nature when ridden with a bit of wheelspin (wheee!). At the end of the day, we returned to the Hotel and cleaned up for an oddly fish-centric dinner, punctuated with the rude comments and off-color jokes that can only be told by a bunch of drunk & jetlagged motojournalists.

I think I remember belching a tequila flavored prayer into my pillow before I lost conciousness.... It went something like this: "Please lord, let the track be clean and dry tomorrow, cause I think velocity is an excellent hangover cure."


Day 2 - The Track

As luck would have it, we arrived back at Almeria with the snow-covered peaks of distant mountains clearly visible beneath sunny skies.be a great day. For the morning's sessions, we would be riding on the stock Bridgestone BT-014 OEM street tires, followed by a post-lunch switch to Bridgestone DOT race tires. I liked the 014s on the street, due to their good wet grip and neutral steering.

They continued to impress on the racetrack, with impressive dry grip and good consistency. However, it was the race compound tires that really got me excited about the ZX-6R's new engine. You see, the street tires caused me to be a bit restrained with the loud handle and once we switched to race rubber, I was more inclined to probe the new bike's limits.

Those limits are lofty indeed. The new engine's power is very much like a GSX-R 750 and with the ZX-6R's light weight and nimble handling, the acceleration off of corners is highly entertaining. When hard on the gas on race tires, the bike wants to wheelie through the rapid right-left transition between turns one and two.

Those wheelies are caused not just by abundance of power, but also by the fact that I'm able to dial-in exactly the amount of power that the tire can handle through those transitions. It seems that when an engine is this manageable, you find yourself using more of what it has to offer.


Unfortunately, though the brakes offer excellent power and feel, the new radial master cylinder is mounted so that it comes into contact with the fork leg and prevents the brake lever from being rotated-down far enough to reach a natural/comfortable hand position. According to an un-named Kawasaki tech, this problem made it to production because most of the Japanese development riders are fairly short, so their wrists approach the grips & levers at a flatter angle.

However, like most American riders, my wrists approach from above and rotating my hand up to reach the brake lever is both uncomfortable and time consuming. My only other nit-pick is with hard (racing) up-shifts near redline on the straights.

These shifts are often met with the slightest of wiggles from the bars (see videos) and I get the distinct impression that you wouldn't want to try them one-handed. Don't get me wrong, the bike is much less likely to shake its head than the '03-'04 ZX-6Rs were, but it still lets you know that there isn't a steering damper working under that fairing. There you have it, you've just read my only complaints with the 2005 Kawasaki ZX-6R.

Could you wheelie with this fat guy sitting on your back?

Get the picture? This thing rocks! The powerful brakes and excellent slipper clutch allow smooth corner entries, with deep trail braking and drama-free downshifts, lap-after-lap.

Mid corner stability is better than the previous ZX-6R, but not quite as rock-solid as a CBR 600RR. However, mid-corner line changes and clumsy shifting of my considerable body weight didn't phase the 6R.

Another thing that impresses me, is that the ZX-6R's suspension and tire feedback is nice and clear.

This comes in handy not only for changing surface conditions on the street, but also for aspiring racers who are trying to select tires and sort suspension settings.

Even though the Kawasaki's feedback is a useful diagnostic tool, aside from rotating the levers as far-down as they would allow, the only things I needed to change throughout the entire day were gas and tires.

600 Class "Trackbike" Score: A+


What we have here is a weapon. It's light, nimble and silly fast, while being refined, consistent and fairly comfortable. If you ride a lot of twisties and/or terrorize track days, this bike needs to be at or near the very top of your shopping list. I have no idea how they do this year-after-year, but the Japanese have redefined what it means to have open-class power in a middleweight package.

It used to be just marketing hype, it's now reality.

Liquid-cooled, 4-stroke In-Line Four
636 cm3
Bore and Stroke
68 x 43.8 mm
Compression ratio
Valve system
DOHC, 16 valves
Fuel system
Fuel injection: ø 38 mm x 4 (Keihin) with oval sub-throttles, dual injection
Forced lubrication, wet sump
6-speed, return
Final drive
Sealed Chain
Primary reduction ratio
1.891 (87/46)
Gear ratios: 1st
2.923 (38/13)
2.055 (37/18)
1.666 (35/21)
1.450 (29/20)
1.272 (28/22)
1.153 (30/26)
Final reduction ratio
2.866 (43/15)
Wet multi-disc, manual
Perimeter, pressed-aluminium
Wheel travel:
120 mm
135 mm
Tyre: front
120/65ZR17M/C (56W)
180/55ZR17M/C (73W)
Caster (rake)
106 mm
Steering angle (left / right)
27° / 27°
Front: Type
41 mm inverted cartridge fork with rebound and compression damping, spring preload adjustability and top-out springs
Rear: Type
Bottom-Link Uni-Trak with gas-charged shock, spring preload adjustability and top-out spring
Compression damping Stepless
Rebound damping Stepless
Type Dual semi-floating 300 mm petal discs
Caliper Dual radial-mount, opposed 4-piston, 4-pad
Type Single 220 mm petal disc
Caliper Single-bore pin-slide
Overall length 2,065 mm
Overall width 715 mm
Overall height 1,110 mm
Wheelbase 1,390 mm
Ground clearance 120 mm
Seat height 820 mm
Dry weight 164 kg
Fuel capacity
17 litres
Maximum power
95.5 kW {130 PS} / 14,000 rpm (EUR/AUS)
92.5 kW {125 PS} / 12,500 rpm (USA/CAN)
90.8 kW {123 PS} / 12,500 rpm (MYS)
78.2 kW {106 PS} / 13,000 rpm (FRA)
Maximum power with Ram Air 100 kW {136 PS} / 14,000 rpm (EUR/AUS)
97 kW {132 PS} / 12,500 rpm (USA/CAN)
Maximum torque 70.5 N·m {7.2 kgf·m} / 11,500 rpm (EUR/USA/CAN/AUS/MYS)
63 N·m {6.4 kgf·m} / 11,500 rpm (FRA)

The specifications mentioned here apply to and have been achieved by production models under standard operating conditions. We intend only to give a fair description of the vehicle and its performance capabilities but these specifications may not apply to every machine supplied for sale. Kawasaki Heavy Industries, Ltd. reserves the right to alter specifications without prior notice. Equipment illustrated and specifications may vary to meet individual markets. Available colours may vary by market.


  • Uprated, liquid-cooled, DOHC, 16-valve 636 cm3 In-Line Four engine delivers increased performance, especially in the higher rpm ranges.
  • New cylinder head design locates each pair of intake/exhaust valves farther apart for improved breathing and higher combustion efficiency.
  • Complementing the new head are new pistons with reshaped crowns and improved, low-friction skirt profiles.
  • Larger diameter intake and exhaust valves, together with new cam profiles, contribute to the new engine's enhanced performance. The new 6R gets the 03MY racing kit intake and exhaust cams.
  • Large-bore 38 mm throttle bodies feature oval-shaped sub-throttles (measuring 56.1 x 46 mm) that allow airflow to be increased without the need to increase the throttle body pitch (hence the engine width does not need to increase and a slim riding position can be maintained). The additional intake area improves intake efficiency by 20%, contributing to the new engine's increased performance. The use of oval-shaped sub-throttles is the first adoption of this technology in the motorcycle industry.
  • Dual-injector digital fuel injection system features extra-fine atomisers in the throttle bodies and a set of secondary injectors located in the airbox. The result is improved cylinder filling, crisper throttle response and higher power output.
  • The new fuel tank design improves mass centralisation and allows the use of a larger-capacity airbox, which further improves intake efficiency.
  • Another important new feature is the addition of an exhaust valve. Integral with the new under-seat muffler, this device controls the pressure waves inside the exhaust system, contributing to improved low- and mid-range power characteristics.
  • Larger capacity radiator improves cooling efficiency. The new radiator is 40 mm taller and features more tightly packed cores.
  • Controlling the new engine is a new ECU, with added memory for the exhaust valve and for the second set of fuel injectors.
  • Like the 6RR, the new 6R clutch is fitted with a back-torque limiter. This reduces rear-wheel hop that may occur when downshifting at high rpm.
  • Shifting quality is also better, thanks to a bearing fitted to the shift-drum locator arm.
  • 3rd gear ratio is taller, for better spacing between the gears.
  • Strong needle bearings used at the ends of the transmission shafts contribute to transmission durability.
  • Fully adjustable Showa fork delivers improved ride quality and outstanding cornering performance.
  • Race-developed Bottom-Link type Uni-Trak rear suspension delivers a smooth ride and excellent cornering performance. New linkage ratios give more linear action, and improved settings for the rear shock improve both ride quality and track performance.
  • New all-aluminium perimeter frame offers exceptional strength and torsional rigidity while delivering responsive and stable handling performance.
  • The new frame reduces the distance between the swingarm pivot and steering head by 13 mm, contributing to the shorter wheelbase and allowing use of a longer swingarm. Wheelbase: 1,397 > 1,390; Rake: 24.5° > 25°; Fork offset: 26 mm.
  • Forward-located swingarm pivot and long swingarm reduce the leverage of the rear sprocket on the rear suspension, resulting in superb rear suspension action.
  • New braced aluminium swingarm is significantly more rigid and resembles that used on the Ninja ZX-10R. The new swingarm uses a cast section at the pivot, with bracing on the right side. The left arm is a reinforced extrusion. The exhaust pipe for the under-seat exhaust passes through the swingarm.
  • Improved, centrally mounted Ram Air duct is integral with the steering head. By reducing air resistance inside the Ram Air ducts, Ram Air efficiency has been improved, contributing to the increase in power output. (Illustration H)
  • Steering head uses ball bearings for light, responsive steering.
  • Radial-mounted, 4-piston front brake calipers deliver exceptional feel and performance - widely used in racing, the 03MY 6R and 6RR were the first production bikes in their class to feature this style of brake caliper. Four independent brake pads are used - one for each piston - for more even wear and improved heat resistance.
  • Large-diameter, semi-floating, drilled, 300 mm stainless steel petal front disc rotors are 5.5 mm thick for high heat capacity and mount on disc carriers without offset to reduce weight.
  • Radial piston front brake master cylinder uses direct action for improved control and better feel at the lever.
  • Brake lever is 5-way adjustable.
  • Small diameter petal rear brake disc measures 220 mm in diameter for low unsprung weight.
  • Compact, lightweight rear brake caliper mounts directly to the swingarm, negating the need for an independent brake tie-rod.
Wheels / Tyres
  • New, ZX-10R-type wheels are light and increase the family resemblance of the Ninja series. The front is the same as the ZX-10R's, but with a smaller 25 mm axle. The rear wheel features the same design as the 10R's, but with a smaller rim size.
  • Rear wheel features a wide 5.5-inch rim. Front rim measures 3.5 inches.
  • High-spec front and rear tyres deliver exceptional cornering performance.
  • Tyre sizes: Front: 120/65ZR17M/C (56W)
    Rear: 180/55ZR17M/C (73W)
  • New cowling design dramatically improves the bike's aerodynamic performance, while enhancing the "Ninja family" look. The new ZX-6R has the lowest CdA of any Ninja released to date.
  • The new bodywork moves the point where the boundary layer separates from the upper cowling rearward, while moving the point of separation from the lower fairings forward. This significantly shortens the point of convergence at the rear of the machine, greatly improving the bike's aerodynamic efficiency. It also reduces turbulence around the rider, but more importantly, this design allows a greater possible top speed and quicker acceleration.

  • Under-seat muffler contributes to improved aerodynamics and gives the new 6R a slim, racy look.
  • All-new bodywork with MotoGP styling elements gives the machine a distinctively racy look.
  • 10R-style cowling with "hungry" central Ram Air duct and very bright dual multi-reflector headlight gives the front of the bike a very aggressive look.
  • European models feature front turn signals stylishly integrated in the bodywork for improved aerodynamics. Rear turn signals are extremely compact and feature a conical design. (North American models feature compact new front and rear turn signals like those on the Z750S.)
  • Flush-surface LED tail light like that of the 10R curves up slightly over the top of the seat cowl, making the 6R very visible to the drivers of high vehicles.
  • Aerodynamic front fender is the same as on the Ninja ZX-10R.
  • Optional single seat cover can replace the tandem seat for an even more aggressive image.
  • Racing-style instrument panel features a bar-type LCD tachometer, digital LCD speedometer, an adjustable shift indicator lamp, and a stopwatch-style lap timer - this in addition to digital temp gauge, clock, tripmeter and a comprehensive range of indicator lamps. The shift indicator lamp has three settings: Off, Low and Bright.
Other Touches
  • Matt-black frame and swingarm enhance the 6R's racy look.
  • Upper triple clamp has holes for a stylish appearance and lighter weight.
  • Newly designed passenger peg brackets are very stylish.
  • All-stainless exhaust system.

  • Revised riding position is based on that of the Ninja ZX-10R. The pulled back steering head reduces the distance between the handlebars and the footpegs. The new frame, seat and fuel tank locate the rider "in" the bike, giving the rider a very confident feel. Handlebar, seat and footpeg locations give an ideal position for high performance riding with a good level of comfort.
  • The redesigned fuel tank features a depression in the top surface of the tank cover so the rider is able to tuck in better, for improved aerodynamics.
  • The new cases mount the cylinder at a more vertical angle (25° to 20°), allowing the engine to be mounted further forward in the frame.
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