What's it share the crank with that's in the US, the GSXR600?
(The GSR 600 & GSXR 600 are 67mm x 42.5mm - so it sounds like it.)
If that's the one, what's the advantage of using a 600 motor that's sleeved down to a 400? Why not just put a 600 motor in it? Or is the class limited to 400's? If that's the case, isn't the 465 a cheater motor?