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. 

Now that it’s May, 2022, there’s a strong expectation that the ZX-4R could make its debut later this year, possibly as a 2023 model. While that would be exciting—particularly if speculation about the engine is accurate—there's a twin theory now making the rounds. It’s difficult to say at this point if it’s much more than simple, wishful thinking, but when you read it, you may join us in hoping that it’s true. Ready? Young Machine is now speculating that, alongside the ZX-4R, there could also be a Z400RS on its way. 

The math here gets a little muddy. The likelihood seems high that the ZX-4R engine will be based on the ZX-25R's engine, only with a little extra displacement. While the existing Z650RS features a parallel twin, its bigger, meaner neo-retro sibling, the Z900RS, gets its power from an inline four. So, even within the existing RS lineup, it’s clear that bikes don’t necessarily need to conform to a specific engine configuration in order to be members of the RS family. 

If a Z400RS becomes a reality, is it likely to make its way outside of Asia? That depends. A whole lot of markets do seem to love their neo-retro bikes. While the U.S. isn’t super keen on what we view as smaller-displacement bikes, it seems like a Z400RS could potentially do well in Europe. There are a whole lot of “ifs” here, as there usually are with rumors—but while we’ll probably be envious if and when a Z400RS makes an appearance in Japan, we’ll also be happy for riders. Plus, we should be used to that cool-bike-only-sold-in-another-market envy by now. 

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