How to turn your ZX-6R 636 into a track weapon
The Kawasaki ZX-6R 636 comes with a road-friendly suspension setup as standard that left us a little disappointed on track. Can twiddling the adjusters really be enough to transform it?
It’s not just the ZX-6R that could benefit from a little work with a screwdriver. When was the last time you sat down and had a proper fiddle with the suspension adjusters on your bike? When you first picked it up from the dealer? At that trackday last year? Or not at all? It’s funny, for years we criticized manufacturers for supplying bikes with bugger-all adjustment on the bouncy bits and, now they’ve relented and given us the opportunity to screw things up, most of us hardly ever touch them. Admittedly, most sports bikes these days come with a base suspension setup that’s plenty good enough for most riders, most of the time. That’s a legitimate argument, but ask yourself this, did you buy the bike in the first place because it was ‘plenty good enough, most of the time’? And you’d be surprised at the number of bikes we’ve seen that come out of the showroom or off the production line with the suspension in a random configuration.
The Kawasaki ZX-6R 636 was the bike that kicked off this whole suspension discussion in the SB office. For 2013 the green team took a half-step away from razor-sharp track-chomping 600cc supersport race replicas by adding 37cc to the engine capacity. The extra capacity gave the Ninja a chunk more torque, making it a more useful and, ultimately, faster road bike. To go with the better road manners of the motor, Kawasaki gave the suspension a good going over too. The result was a more supple, more compliant ZX-6, that sucked up bumpy roads and laughed at the super-stiff Yamaha R6 as it became a green dot on the horizon. Perfect. Except that when we did our big supersport 600 group test last year, we took them all to a race track and hammered them for lap times. The 636cc motor was really impressive, pinching some of the Yamaha’s screaming top end and blending it with a lump of the Triumph 675’s mid range. The result was a bike that was as quick at the end of the straight as it was off the corner. It also needed the least gear changes to put in a quick lap, another testament to the good spread of power.
But the chassis was the Ninja’s downfall on track last year. The improved comfort and road manners were at a cost to the performance on track. When pushed hard, the forks would bottom out on the brakes, and with aggressive inputs it was hard to get the chassis to settle. You could get quick laps out of it, but riding it hard was like sprinting while holding a bottle of water with the lid off – possible if you’re smooth, but sooner or later it would get messy. But what was most frustrating was how the engine, brakes and slipper clutch were rock solid and egging you on the whole time. Just how good would the ZX-6R be with a proper track setting in? And, more to the point, would it need major suspension work to put right, or could the standard twiddly bits do the job?
On the middleweights test last month, we hit up Chuckwalla Valley Raceway (CVR) in the USA, to put the MV F3 800, Ducati 899 and Suzuki GSX-R750 through their on-track paces. We had a Kawasaki ZX-6R 636 at our disposal too and, aside from providing a handy comparison to the engine performance of the others, it gave us a chance to answer the question of the chassis’ potential. Y’see, Kawasaki had already been to CVR with the 636 for some pre-test testing. Armed with an AMA Supersport chassis technician and a rapid test rider, they’d dialed in the ZX-6R’s suspension to suit the circuit. There was no nod towards road comfort, no concerns about the seat height putting off novices; all that mattered was going round in circles as fast as possible. Save for one simple 8mm spacer above the rear shock, nothing was physically added or taken away from the suspension. In other words, for the price of an 8mm thick washer and fifteen minutes on the tools, the bike was turned from a comfy road tool to a track day weapon.
So, what’s changed? Well the full setup is included in the section below marked “Make my ZX-6R into a supersport bike”, but the biggest changes are to the attitude of the bike. The forks are pulled through the yokes further, sharpening the head angle to make the bike steer quicker. The 8mm spacer in the rear shock does the same thing by raising the rear of the bike and also lifts the centre of gravity, making it change direction faster. More preload starts the bike higher up in the suspension stroke, reducing the chance of bottoming out and lifting the centre of gravity some more. Also, by working higher up the stroke, you tend to get more feedback. Damping wise, we’re talking a little more control of how the bike’s weight shifts – slightly more rebound and compression damping to keep it calm when the rider goes nuts.
First leg over and the changes are immediately obvious – the floor has vanished. 8mm more at the shock means the seat is some 15mm higher. That’s not enough for me to need a step ladder, but definitely enough to for me to spot it straight away. Rolling across the paddock and into an out-lap, everything feels pure ZX-6 – nice high bars, superb brakes and, ah yes, there’s that motor. Over the bumpier parts of the track at first-lap speeds, the ZX-6R feels stiffer, more taut than before. On a road ride, this translates into tiresome kicks through the bars and seat, but on track it’s all feedback coming straight to the rider for reference next apex. I start putting in laps and everything goes into a blur until I’m tripped up by the man with his chequered flag. Shit, forgot to pay any attention to what the bike was doing. Halfway through the next session on the Ninja, it’s happened again. I get a few corners in and, just as I’m making mental notes about it being impossible to miss an apex, everything goes fuzzy. A few good apexes and it tricks you into thinking you’re a racer – everything except the lap timer goes out the window. With this setup in it, the 636 feels like a race bike. It’ll steer into an apex as fast as you could possibly want. Changing direction is only limited by how hard you want to countersteer – it goes from one knee to the other with out wallowing or grumbling. The feedback on the edge of the tyre is improved and I can now trail the brakes deep into a turn without worrying about bottoming the fork. The only negative effect, aside from comfort, is an increased tendency to shake the bars on fast direction changes. It’s a trait I can live with for how much of an improvement there is elsewhere.
I’ve never touched the suspension on my bike, should I?
Well, no, not if you’re completely happy with the way it handles and feels. If you’ve never experienced anything better, you’re probably perfectly happy with what you’ve got. Lucky you. But if there’s something bugging you about it, then make sure you have a play with the adjusters before you trade it in for something that feels better. You won’t be the first or the last person to decide you don’t like a bike because it’s too harsh on the road, but before you give up on it, check the suspension. You might find that a previous owner had wound the compression damping up to full, and you’ve effectively been riding a rigid GSX-R600. If you’ve never so much as looked for the rebound damping adjusters, do yourself a favour and check the bike is on its standard suspension settings. The actual settings should be in the owners manual or available from any decent dealer. You could go asking on internet forums, but bear in mind that for every well-informed, factually correct post, there are about twenty well-meaning posts, trying to be helpful, but in reality just guessing. Remember, damping clicks or turns are counted back out from fully closed (almost always fully clockwise).
Make my ZX-6R into a supersport bike
Kawasaki ZX-6R 636 track settings
Pull through height above top yoke: 9mm
Spring Preload: 11 turns (from fully anti-clockwise)
Compression damping: 5.5 turns (from fully clockwise)
Rebound damping: 4.5 turns (from fully clockwise)
Height: 8mm spacer on top shock mount
Preload: 6 turns (in from stock position – see manual)
Compression: 2.25 turns (from fully clockwise)
Rebound: 1 turns (from fully clockwise)
So was it any good?
I have to say, although I expected an improvement from changes to the suspension settings on the 636, I wasn’t convinced it would be enough. And, given more time and further development, then alterations to the spring rate and oil height would definitely reap more benefits. And once you’ve reached that point, it would be worth uprating the forks and rear shock to give more consistent performance throughout a session. But I was genuinely impressed with just how much better the Ninja was on track with simple, good old-fashioned adjustment. On the standard settings, I found myself getting frustrated with the suspension and, ultimately, pushing it harder would have led to a crash. With the track settings in, the limiting factor was pushed back into my court – how hard did I want to push and how much strength did I have to hold on with? That’s a pretty impressive change from a man with some screwdrivers. If you’ve got a 2013 Kawasaki ZX-6R 636, then bung these settings in for your next track day. You’re welcome.