More details on the 636cc ZX-6R

Kawasaki has made a radical move with the latest version of the ZX-6R, the bike which was named top 600 in the annual MCN awards last October.

It has created a whole new category – a sports 600 with a bit more on top. The new ZX-6R has just outgrown its rivals.

Despite the new 636cc capacity, the majority of the 2002 engine is identical to the 2000 model’s.Kawasaki’s engineers have simply increased the bore diameter by 2mm from 66mm to 68mm without touching the stroke at all.

That was a straightforward task as when the cylinders got aluminium liners rather than steel ones, there was a lot of metal left over around the cylinders – which is why big bore kits became popular.

To compensate for the bigger bores, the engine cases have been redesigned to increase the gasket area. In addition, a new head with a revised squish area has been designed to work with the increased displacement.

Tuner Ray Stringer has worked on loads of Kawasakis and he reckons the new capacity is a great idea. He said: " It will make it a much nicer bike. As Kawasaki has increased the bore and not the stroke, the top end will be up but it will improve rideability as well – it will be less peaky, with more midrange. "

An insider added: " The extra 37cc will give the bike more power and torque and make it better for the road. The slight increase in capacity will make the difference where the rider needs it most – in the midrange. By boring out the cylinders Kawasaki has managed to give the bike a boost in performance without affecting the handling at all. "

MCN’s Marc Potter, who has ridden every major 600 for the last six years, said: " Kawasaki are very clever at making subtle tweaks to long-running models and making them feel like very different bikes. When the current ZX-6R was launched no-one really expected much from it, but it felt like a completely new bike.

" In the past I’ve ridden specials with slightly more capacity than standard and though an extra 37cc doesn’t sound like much it should make a big difference to the way it rides, especially on the road, where the ZX-6R is already a great bike.

" Though it’s slightly bigger than most of the current 600s, for many people that makes it a better bike than something like the very powerful but tiny GSX-R600, so maybe Kawasaki has done the right thing by leaving the rest of the bike pretty much as it was. "

That performance boost could well mean a top speed higher than the 2001 bike’s 166mph, which made it the fastest 600 MCN has ever tested. Add to that more punch between 6,000rpm and 10,000rpm and you’ve got some idea how much difference 37cc makes.

No official power figure has been released, but sources close to Kawasaki say the top end is boosted by 6-10bhp – enough to put the real rear wheel power above the magic 100bhp.

The extra capacity and power could tempt riders who would otherwise be looking at the ZX-7R or a GSX-R750. It might also attract buyers who can’t stretch to a 750 and in marketing terms it seems a clever move from Kawasaki, as riders might feel they’re closing the gap on the next bigger bike.

Though the bored-out engine is the major change, there have been minor tweaks elsewhere. The fork internals have been slightly revised, with a new finish on the interior of the sliders which helps give them a smoother action. Damping rates have also been adjusted to improve the feel from the front suspension. The shock remains untouched.

The aluminium frame is unchanged, too, as are the brakes, apart from a repositioning of the front master cylinder so it doesn’t obscure the tachometer.

The rest of the engine and carburation system remains the same, apart from the gear shift shaft, which has been increased in diameter for smoother changes.

Kawasaki has decided to stick with carbs and not move to fuel injection – something else which sets the bike aside from all the other sports 600s.

The 2002 bike will be available in three colours – green/black, red/black or silver/black – and will be instantly distinguishable from the old model by a large " 636 " logo on the fairing.

A similar figure seems unlikely to appear on rival bikes, though – other firms seem happy to let Kawasaki go it alone. A Yamaha spokesperson said: " We have absolutely no plans to increase the capacity of the R6. It is the ideal balance of power and handling. "

And despite Suzuki’s recent revelation that it is enteringinto an alliance with Kawasaki, this is one thing it will not be sharing with its new partner. A spokesman said: " Our 600 is very strong and we already have the 750, so we don’t see the need to increase the capacity. "

Even though insurance premiums are based partly on capacity, it seems unlikely the ZX-6R’s 37cc is a big enough increase to affect the amount you’ll pay for cover. According to a Norwich Union spokesman, the bike should remain in Group 14.

But while the capacity hike shouldn’t affect road riders too much, it will certainly make a difference to racers – no 2002 ZX-6Rs will be able to take part in Supersport races next year as they will exceed the 599cc limit.

But it’s not all bad news for racers. There will still be 2002 bikes on the grid in the U.S., where the ZX-6R won’t get the capacity hike.

Though Kawasaki sources in Europe have said the Japanese factory no longer sees racing as a priority, it seems to have been swayed by the popularity of the AMA Supersport series and its success in it with rider Eric Bostrom, Ducati World Superbike star Ben’s little brother. He won the last race at Pikes Peak, Colorado and currently leads the title race.

This has opened the door for the possibility of an SP version next year, according to Harald Eckl, boss of the Kawasaki World Superbike and Supersport teams. He said: " We will run the 2001 bike next year, but for 2003 there is the possibility of an RR version using a 600cc engine. But I don’t know if it would be in production. "