A Kawasaki 400cc four-cylinder with 70 hp?

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Homologation data for the Kawasaki ZX400SP and -PP has recently surfaced in the US. It represents the new Kawasaki ZX-4R high-revving four-cylinder power source.

In Asia and Australia, the 17,000 rpm 250cc four-cylinder ZX-25R was a real hit. With that 250 came rumors of a ZX-4R. Until unconfirmed reports surfaced in the US, it was accompanied by rumours. In the homologation data, in addition to the well-known 400 twins, two new variants are mentioned, the ZX400PP and -SP.

Behind that compact seems to be a new engine block, a 399cc four-cylinder. It looks like Kawasaki will indeed launch a new sporty four-cylinder in the US. By the way, the photos show the current ZX-25R. The latter squeezes out 45 hp from a cylinder capacity of 249 cc. The torque is also 23 Nm. Bored and high-stroke, the displacement increases to 399 cc, and the block evokes memories of the earlier ZXR400 that produced 62 hp and 43 Nm in 1989 and later revved to 14,000 rpm. With the all-new ZX-4R, that power should at least be achievable, but due to current emissions regulations, torque will be a maximum of 40 Nm.

Our Japanese colleagues young-machine.com Mention 70 hp and confirm it as follows: the TT-F3 class from the 80s/90s serves as a reference, where a four-stroke 400cc four-cylinder semi-factory group can reach a maximum of 80 to 90 horsepower according to the time, according to the technicians. Admittedly, these weren’t ordinary production engines at the time, and the emissions requirements – if any – weren’t very strict. But with modern technology, 400cc four-cylinders should be able to tap more than 70 hp, including modern injection, 13:1 or higher or very high-speed compression.

The ZX-25R’s four-cylinder produces 45 horsepower. Bore x stroke 50 x 31.8 mm and compression 11.5 : 1. Japanese press young-machine.com A 400cc engine with a 5mm larger bore and 10mm more stroke is calculated to easily achieve over 70hp.

Kawasaki could present the ZX-4R at the Japanese showroom as early as 2023. Given the stricter emissions requirements of Euro5 and beyond, it’s unlikely such an engine will even make it to Europe.

Awesome video of the ZX-25R with turbo back below: