Here's what possible from 400cc V4... 94 hp!! That makes up for porky +400lb weight somewhat
https://mngforce.typepad.com/nc450vd...11-engine.html
If ZX-4R inline-4 ever makes it to U.S., they can work similar magic with it.
They've got Ninja 400 twin up to 61 hp now. Mighty impressive for 300lb bike!