Likely derived from the ZX-25R.
When Kawasaki launched the Ninja ZX-25R sportbike in Asia last year, sportbike aficionados were gushing due to the bike's unique configuration. Designed as a race-ready machine out of the box, the ZX-25R features an engine unlike any other found in production motorcycles of today. Its 249cc inline-four cylinder engine made all the right sounds to conjure up images of the heyday of motorcycle racing.
With a redline of 17,000 rpm, and a maximum power output of 50 horsepower, Kawasaki produced an outstanding modern-day evocation of the racing bikes of the 80s and 90s. That said, Kawasaki has always been about adopting its rich racing heritage into the modern day. With bikes like the ZXR400 seeing massive popularity in the late 80s and early 90s, motorcycle enthusiasts of today don't really have many brand new options, should they wish to experience the exhilarating sound and linear performance of a small-displacement four-banger with a sky-high rev limiter.
Apart from the ZX-25R, no other bike in the market offers a low-displacement inline-four motor. However, we could soon have another machine follow a similar formula. Unsurprisingly, it's from Kawasaki themselves, as speculations have been circulating that Team Green has a new sportbike under development in the form of the ZX-4R. Now, rumor has it that Kawasaki has employed a rather simple formula for the ZX-4R. By increasing the displacement of the ZX-25R's mill by way of enlarging the bore and swapping out the pistons and crank, they could eke out just a tad more horsepower and torque.
The ZX-25R has always been seen as a track-focused machine with its peaky powerband and sky-high rev limiter. Could the ZX-4R, assuming it does come into existence, serve as a more street-focused machine, thanks to better low-end torque and overall drivability? While everything about the ZX-4R is pure speculation, multiple motorcycle publications in Japan continue to keep the rumor mill turning. Having said that, you all saw how quickly the Yamaha YZF-R7 transformed from pure speculation to an actual, production-ready machine. If that's anything to go by, then I can surely say that I'm super excited for the Kawasaki ZX-4R.