Kawasaki ZX-15 | Coming Soon

A supercharged superbike?

By Ben Purvis, Illustration by Motorcyclist Japan

Recent power increases in 1000cc superbikes, many of which now produce nearly 200 crankshaft horsepower, have created a problem for hyperbikes like the Kawasaki ZX-14 and Suzuki Hayabusa. Once the flnal word in top speed and fiat-out acceleration, these road-burning behemoths are now regularly outperformed by lighter, nimbler literbikes in a straight line as well as around corners. The solution? Take advantage of the fact that unlimited-class machines have no race regulations to conform to and add a huge extra dollop of power in the form of a supercharger.

No fewer than four new patent documents reveal that Kawasaki is working on a supercharged four-cylinder motorcycle as a potential replacement for the ZX-14. One, titled “Two-wheeled motor vehicle with supercharger,” covers the overall layout of the bike. The supercharger is located behind the cylinder block and underneath the throttle bodies, and gear-driven directly off the crankshaft. Fresh air enters between the headlights, then runs over the engine and down to the supercharger, where it’s compressed and fed back to the throttle bodies.

This is not uncharted territory for Kawasaki. The firm already uses a remarkably similar supercharged four-cylinder engine in its Ultra 300X personal watercraft. With a slightly larger, 1500cc capacity and an intercooler attached to the supercharger, the Ultra 300X is rated at 300 bhp. Even without an intercooler—no evidence of any is shown in the motorcycle patent documents—a supercharged ZX-15 should still produce at least 250 bhp at modest, reliable boost levels.

A supercharged streetbike has been rumored to be under development at Kawasaki since 2009, and this year there are already rumblings in the Japanese press that the ZX-14 will be replaced and/or updated for the 2012 model year. This could be the perfect opportunity to add the supercharged version to the range. Relatively low development costs—adding forced induction to an existing engine is far cheaper than developing an entirely new powerplant—makes this an even more likely situation. Still struggling against a depressed sales environment, Japanese manufacturers like Kawasaki are looking for every opportunity to create excitement without incurring excessive expenses. Look out, Hayabusa riders!

By Ben Purvis
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