When Kawasaki launched the ZX-25R in 2020, everyone wishing for the halcyon days of tiny-displacement four-cylinder Japanese sportbikes collectively gasped. If you thought the days of a small-displacement, high-revving bike bringing an instant smile to your face were a thing of the past, it seemed that Kawasaki was here to prove you wrong. Except, of course, if you didn’t happen to be located in Japan or any of the Asian markets where the ZX-25R has since been sold—if you lived elsewhere, sadly, you were out of luck.
Still, the ZX-25R's popularity in the ensuing years has been strong. When an OEM has a hit on its hands, what does it want to do? Frequently, it wants to expand on that hit and see if lightning will strike twice. Thus, it wasn’t a huge surprise when rumors started swirling that Kawasaki was working on a ZX-4R, which would be a 400cc sportbike based on the inline-four architecture found in the existing ZX-25R. At one point, Japanese magazine Young Machine even spotted what seemed to be a ZX-4R out testing on public roads.
