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- Written by Carole Nash Editor
- Created: 19 June 2008
Some bikes are simply brilliant at almost everything you can ask of any two wheeled device, and the ZX6R Ninja is one of them.
A fantastic handling, 160mph blur of speed and aggressive styling, it also has brakes to pop your eyeballs and is surprisingly comfortable on longer trips too.
Evolving from a long line of four cylinder, DOHC, water cooled, 600cc flyers stretching all the way back to the GPz600 of 1984, the ZX6 has consistently proved itself to be one of the most exciting mid-sized sports machines that money can buy.
Talk about a tough act to follow. The Valencia grand prix circuit is the current fave spot for bike manufacturers to introduce their hot new machinery, and the memories were still fresh as I threw a leg over the ZX-6R in the Spanish sunshine.
Just a few weeks earlier I´d been carving laps here aboard Yamaha´s mighty YZF-R1. Shortly before that, Aprilia´s RSV Mille R had provided an exotic, Ohlins-suspended introduction to the circuit. So the pressure was on Kawasaki´s revamped middleweight as it headed up the Valencia pit-lane and out onto the track.
Of course, the green team´s contender has faced stiff competition before, not least from its own classmates. Less than two years ago the ZX-6R was ripping onto magazine covers beneath the headline "World´s Best 600", only to find itself relegated to also-ran status by Yamaha´s YZF-R6 just 12 months later.
Kawasaki´s response? A subtly reshaped ZX-6R that is harder, faster, lighter and more powerful.
Visually the most obvious difference is up front, where twin headlights now sit above a larger, even more aggressively gaping intake mouth. Despite new paintwork the rest of the ZX-6R looks familiar, but closer inspection confirms that powerplant, suspension, swing-arm and brakes are all new, or at least seriously tweaked.
Engine work starts with those ram-air ducts, which are reshaped to improve flow. Intake port length is reduced by 7mm, which alone ups power by one, ah, donkey, and moves the redline from 14,000 to 14,500rpm. Inside the engine a reshaped combustion chamber, developed from the ZX-7R factory racebike, allows a compression ratio hike from 11.8 to 12.8:1.
The 599cc lump´s 66 x 43.8mm dimensions (the most oversquare in the class) are unchanged but new cylinder barrels have an all-aluminium ‘closed-deck´ construction, with no liners. Kawasaki says this makes them lighter, harder-wearing and gives better heat dispersion. Along with remapping of the ignition, the result is that the new ZX-6RJ delivers a claimed max of 109bhp at 12,000rpm, 3bhp up on last year´s G model.
Weight loss was the other half of the engine tuner´s brief, and the first step was to add the valve and clutch covers to the list of bits, including alternator and countershaft covers, that were already cast in magnesium. The crank, ignition coils, cams and clutch are all lighter, the latter thanks to thinner plates. Meanwhile the conrods are strengthened to match the increased power and revs, and the generator is uprated to cope with the extra headlight.
There´s no change to the hefty twin-spar aluminium frame but the swing-arm is redesigned to save weight, and the rear shock´s length and linkage are revised. Suspension springs are stiffer at both ends, the front fork legs are slightly wider-spaced, and fork offset is reduced a tad, increasing trail from 91 to 95mm while retaining the 23.5-degree rake.
Front brake still consists of twin 300mm discs gripped by six-piston calipers. But pads are new and the caliper is redesigned with two 27mm and one 24mm pistons, instead of three of the larger diameter, for improved feel. Tyres remain 17-inchers, but the front Dunlop D207 Sportmax changes from 120/70 to the currently fashionable 120/65 profile, while the rear grows from 170/60 to 180/55.
A new instrument panel saves a little more weight, helping reduce the total to 172kg dry (173kg for California). That´s a handy 5kg down on its predecessor, and within spitting distance of the class lightweight, the 169kg R6. The fairing´s screen is 5mm taller, and the clip-ons now mount below rather than above the top triple-clamp. But the view from the ZX´s unchanged seat added to the familiar feel as I headed out onto the Valencia track, with memories of the R1´s scorching performance here still vivid in my mind.
The main difference between this middleweight and the litre-bike was clear even while I circulated gently to scrub and warm the Dunlops. You gotta rev it, and hard. The ZX has traditionally had strong midrange by 600cc standards, and Kawasaki´s engineers say they were careful not to reduce this when searching for extra top-end power. But on the wide open spaces of the track, coming out of corner with less than eight grand on the dial felt like being stuck in neutral.
Not that this was a problem, because with 14,500rpm to play with the 6R´s power band was more than wide enough to ensure plenty of action every time the throttle was nailed. Once I was dialled-in to the track there was no need to drop below ten grand, better still twelve, especially as the motor´s creamy high-rev smoothness and slick gearbox made wringing its neck an unqualified pleasure.
Valencia´s start-finish straight was barely long enough to shift into top, but the ZX was motoring by the end of it, hitting almost 150mph with a good 10mph more to come. Equally importantly, although the ram-air changes have perhaps quietened things just a little, the Kawi still hurtled through its gears to the accompaniment of a totally addictive whooooah, whooooah, whoooooooooahhhh of induction howl.
The bike also showed new-found ability at the end of the straight, where a squeeze of front brake lever had it slowing perhaps not quite with the ultra-violence of the R1 (the R6 has similar binders, don´t forget), but at a reassuringly rapid rate all the same. Lack of stopping power has handicapped the 6R from its introduction in 1995 right through to last year, but it looks as though Kawasaki has the problem licked at last.
High marks too for handling, which didn´t require much attention yet has been sharpened a touch by the reduced weight and tweaked front end. For track use the bike felt a bit lazy wearing its showroom-stock settings. But a few spanner-turns to raise the rear ride height, a dash of extra shock preload plus a couple of clicks of damping at each end soon had the green machine steering sweetly, feeling firm and planted in turns, and performing outrageously well for an $8099 motorbike.
By the end of a half-hour session the rear end was starting to move around in places, especially the long, fast left-hander near the end of the lap, but this was possibly due more to the tyre than the bike. Although the D207s gripped superbly most of the time, the rear wore much more rapidly than a similar but wider Sportmax had here on the more powerful R1. Dunlop blamed too much shock damping; others the ‘cold tear´ that can occur when a carcass warms up too quickly. Best go back out for another few laps and let them argue...
No such worries next day on the street where the Kawasaki, having proved its added competitiveness on the track, promised to shine just as brightly. It´s a notably roomier, more comfortable bike than the R6, especially if you´re big. The seat is reasonably thick, the pillion gets solid grips, and the taller screen gives a fair bit of wind protection, though as a member of the freakishly tall society I was disappointed to find that it blocked my view of the indicator warning lights.
Carburation is spot-on, allowing the motor to pull in smooth, glitch-free fashion from way low. Through its lower gears the ZX felt positively torquey in the midrange, and it pulled out of hilly hairpin bends with notably more grunt than most middleweights could have mustered. But on the freeway towards Madrid I was reminded that this bike was still a 600, after all, when I wound open the tap at 75mph and 6000rpm in top, heading slightly uphill into a headwind - and the ZX barely moved a muscle until I trod down a couple of cogs.
The chassis never got caught out in similar fashion, and swallowed everything from freeway blast to weather-beaten country roads with style. Its newly firmed-up suspension gave a slightly choppy ride over the worst of the bumps, but the bike´s lightness and agility remained impressive. It was comfortable at freeway speeds, too.
We rode less than 50 of the 250-odd miles to Madrid before turning off, but the 6R felt as though it would have handled the round-rip without breaking sweat.
Heading back towards the circuit for a final blast, working the gearbox to make those intakes sing their 14,500rpm tune at every opportunity, it was clear that the ZX-6R has caused yet another ruffling of 600cc class standings.
On the track last year´s champ, the ultra-light and revvy R6, might still be marginally a better bet. But this sharpened ZX-6R gives away very little even at circuit speeds. And on the road the smoother, torquier, more versatile Kawasaki has enough of an edge to win my vote every time.
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Engine Liquid-cooled in-line four
Claimed power (bhp) 109bhp at 12,000rpm
Compression ratio 12.8:1
Front suspension;46mm cartridge fork, 120mm (4.7in) travel, adjustments for preload, compression and rebound damping
Rear suspension;One shock absorber, 120mm (5.3in) wheel travel, adjustments for ride height, preload, compression and rebound damping
Front brake;2, six-piston Tokico calipers, 300mm discs
Rear brake;Single-action caliper, 220mm disc
Front wheel;3.50 x 17in; cast alloy
Rear wheel;5.50 x 17in; cast alloy
Front tire;120/65 x 17in Dunlop D207 Sportmax
Rear tire;180/55 x 17in Dunlop D207 Sportmax
Rake/trail;23.5 degrees/95mm (3.7in)
Seat height;820mm (32.3in)
Dry weight;172kg (378lb) [173kg/381lb California]
Instruments;Speedometer, tachometer, LCD odometer, tripmeter, clock, LCD cooland temp. display; lights for neutral, high beam, turn signals, low oil pressure
Fuel capacity 18 litres (4.8 US gal)