EPA Documents Reveal 2013 Ninja 300, 400R, Confirms 636cc Ninja ZX-6R

For LRRS club racing, I think so. Probably allowed for other CCS sanctioned series.

Middle Weight Supersport: 4 cyl up to 640cc
Middle Weight Superbike: 4 cyl up to 660cc

Looks like Kawi’s sale tactics is to one up eveyone on displacement to boost sales.