LONG-TERMER: Our Kawasaki ZX-6R

John McAvoy has put almost 300 miles on the ZX-6R in less than a month. Is he happy?

When I spent a few days on the ZX-6R a few issues ago, I was so taken by it that I dropped Kawasaki UK a line and asked if I could keep it on long-term loan. To my delight, the reply came back in my favour and I’m now the proud (if temporary) owner of the very same ZX-6R you saw. And I couldn’t be happier – because I absolutely love this bike.

Typically, the Kawasaki has entered my life at a particularly busy period each year, which means getting any quality time with it has been in short supply. I spend pretty much most of May and June working for Batham’s Racing during the run-up to, and at, the Northwest 200 and Isle of Man TT races, so I’ve been using the ZX-6R mainly to get about locally and on the odd run to collect parts for the team’s race bikes.

So, my time with the Kawasaki has been fairly mundane so far, without even a sniff of getting on track or a meaningful ride that needs more than a couple of tanks of fuel to complete. 

However, during one of my trips to MSS Performance in Colchester in the name of Batham’s Racing – for which sadly I had to use a van – the subject of ZX-6Rs inevitably came up. I say inevitably because MSS are pretty much the go-to people in the country for fast Kawasakis, and we got talking about the latest next-generation supersport rules and how they’ve impacted the Kawasaki. 

In short, they are allowing them to tune the hell out of ZX-6Rs, but the most interesting thing that came up in the chat and which made me prick my ears up was that by far the biggest gain of all the things they can do to the engine is a simple upgrade to a race exhaust, effectively de-catting the standard one, and a re-flash of the ECU. This sounded like something worth looking at more closely.

Some big numbers are mentioned in terms of power gains, so much so that I decide that if it is the case, then the cost of a full replacement exhaust system would be justifiable. Now, this is an important point, because as well as all the stuff I covered in my report on the ZX-6R which makes it so good, by far its price tag is one of the Kawasaki’s most attractive things. Throwing thousands of pounds on upgrades eats into this advantage it has over its similarly priced rivals. But if the gains are big enough, then it’s justifiable.

After some research, it turns out that the catalytic convertors on the Kawasaki are located in the header pipes, then next comes the resonator box, which is mainly to dampen the sound, and then the end can. Once upon a time, the sound-deadening resonator box would be located in the end can, but these days, the end cans on bikes are more or less straight through due to the sound damping stuff being located separately between the end can and header pipes. It is possible to buy just a link pipe, which does away with the resonator box – the equivalent of replacing the end can on a 1990s bike – and no doubt this would make a difference simply due to the exhaust gasses being able to flow better. However, for the exhaust gasses to have the most efficient path from exhaust valve to outside world, the catalytic convertor has to go, too. In short, when once upon a time catalytic convertors didn’t exist on bikes, you just had to replace the sound-deadening end can to get yourself a fully free-flowing exhaust. Today, you need a link pipe to get rid of the resonator box and header pipes to junk the power-sapping catalytic convertors – the scourge of supersport bikes. Basically, you need a full system to get the full benefit. So, I hit the phone to Arrow Exhausts, and it has got a full system on the way to me. The plan then is to take it and the ZX-6R to MSS and do a ‘before and after’ of the bike with the full system – and get to the truth. 

In theory, the hype I encountered at MSS is logical. The supersport bike with significantly less power than a litre bike has to meet the same emission standards, but without the surplus power a litre bike enjoys, and therefore is able to sacrifice some for the convertors to sap. The impact of a catalytic convertor to a supersport bike’s engine performance is much greater. If a catalytic convertor robs an engine of, say, 10 per cent of its power, you’re not really going to notice that if your starting point is 200bhp, but if your starting point is just over 100bhp, you’re going to notice that.

Now, it should be said at this point that the Kawasaki is not a slow bike in desperate need of as much power as can be had to be able to deliver shots of adrenalin – far from it. At the time of writing, having put the test of sub-litre naked bikes to bed, they are all in the same ballpark as the ZX-6R in terms of power output. At no point during that test did anyone say: “I wish these bikes had more power.” 

So, the whole point of de-cating the ZX-6R is only really to see if the hype around releasing what’s already there is a) true, and b) worth the cost.

I may have only done a couple of hundred miles on it so far, but there’s no getting away from the fact that the ZX-6R needs a different approach to riding and a recalibration of the brain. Its wheelbase is a massive 50mm shorter than a ZX-10R’s and 56mm shorter than a BMW S1000RR’s for starters; plus, its rear wheel is half-an-inch narrower, so it wears a 180 section Pirelli Diablo Rosso IV – and, of course, it’s a good 10-15kg lighter than a typical litre bike. So, if you’ve never thrown a leg over a supersport bike, you can probably guess from those dimensions alone what the difference is to a litre bike to ride – you frighten yourself on the way into corners on a supersport bike and on your way out of corners on a superbike. Code Brown moments are equally achievable on both types.