The story appears to trace back to leaked images of a styling model for a new Kawasaki Ninja 250 or 300. Far from being a four-cylinder, it was a proposed revamp for the existing parallel-twin.
The idea of a 250 or 300cc inline-four, harking back to the early 1990s and days of the Kawasaki ZXR250, which made 33kW from its screaming, miniature four-cylinder engine, is tempting. But it’s a dream that would be near impossible to achieve today.
The reality is that Kawasaki may well be developing a new Ninja 250 / Ninja 300 to meet the CBR250RR and Yamaha YZF-R25 / YZF-R3 head-on. But it’s almost certain to remain a parallel twin.
The latest specifications, Euro 4 version of the 300cc engine, as used in the Kawasaki Versys-X 300, already claims over 29kW, just a fraction behind the 31kW of the Yamaha, so power levels are nearly as high as the old ZXR250 without resorting to an expensive four-cylinder. That means the 2014 styling mock-up which sparked this whole fantasy might well emerge later this year as a production Ninja 250 / Ninja 300. But it won’t be a four-cylinder.
Why is it so unlikely that Kawasaki will introduce a inline-four 250cc? A four-cylinder 250cc has more components than a single or twin. Research and Development and production costs would be similar to the new Kawasaki Z900, and it might be more complex – and expensive…
Modern emission rules would be impossible to meet. The engine would rev around 20,000rpm, causing valve overlap and emissions issues at low rpm. The same thing that’s killing off 600cc inline-four sportsbikes would be magnified on a 250 or 300cc four-cylinder.