The engine is utterly ballistic

Ever watched ski jumping? You know, the Eddie the Eagle caper where some dead-eyed Norwegian teenager shuffles to the edge of a precipitous slope, looks into the abyss, then shoves himself over and… whooosh. He’s gone. That’s like hitting 8000rpm on the H2 SX. 80mph… whoosh… 110mph. This is no exaggeration. During a standing start test down the main straight at Estoril I set my Gopro to film the speedo during my slightly duff first run. Taking the time from the video, the numbers go like this: 60mph, 3sec; 100mph, 6sec; 120mph, 8sec; 140mph, 10sec; 160mph, 14sec. Two seconds to go from 120mph to 140 is absurd. The drive at the top-end is instant and ferocious, firing the H2 SX forward with a violence that, on the road, is shocking at first, then addictive. Disengage the traction control (in the interests of scientific experimentation you understand) crack open the throttle above 8000rpm in first or second and the H2 delivers such a wallop of torque that, on dusty Portuguese roads, the rear tyre instantly spins and from there stands no chance of regaining traction. If you’ve never seen a bike with panniers, a touring screen and a nice soft saddle smoke the rear tyre as it leaves the outskirts of town, prepare to: the SX goes on sale in mid-march. Given the reputation of the 2015 H2 as having a Godzilla motor, you might imagine the SX has the same one with a few tweaks. In fact, it’s almost entirely new: the intake system (including the supercharger impeller) pistons, cylinder head, cylinders, crankshaft, camshafts and exhaust system are all new. Only the sump and cases remain unchanged. The reason for the overhaul was… thirst. For the H2 SX to work as a sports tourer, it had to get more than 25mpg, which is what H2 owners put up with if they do more than dawdle. And the Kawasaki engineers didn’t want to lose much power. The solution was to hone the shape of the supercharger’s impeller vanes, tuning them to provide more boost at low and midrange rpm. Because the impeller rotates at 100,000rpm at maximum boost, it only takes tiny alterations to see huge differences in performance. Midrange power (and thermal efficiency) was also increased by dramatically upping the engine’s compression ratio from the H2’s 8.5:1 to 11.2. These and numerous other more subtle tweaks mean the H2 SX’S supercharged intake system is 25% more efficient than the H2’s, meaning it runs cooler too – important if you’re spending all day in the saddle and prefer your testicles unroasted. One downside was that the engine did not make the H2’s hilariously alien gobbling sound on the overrun, so the Kawasaki engineers got to work and the new bike now makes a weird chirping noise instead. It’s so loud you can hear the demented warbler at 100mph. ‘I’m very glad you noticed this is not the same as the H2’s noise,’ says project leader Hiroyuki Watanabe. ‘The noise was important to us, so we changed the impeller design until we got it.’ He also designed-in a hole in the supercharger’s air duct so you can hear it all the better.