As was already written, the 300 cannot RELIABLY be enlarged to a true 400cc without serious issues being overcame. FYI the R3 is actually 321cc, the is KTM is 372cc, and the current Ninja is 296cc. There also is a BMW "310" coming out that is actually 313cc.
I think its entirely possible the "400" would be closer to 375cc with a lot of marketing fluff to come.
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