Don't worry about that one, Grizz just posted on Facebook earlier about the new GO Engine, GX5R piston, 5+2 sleeve & rod in the UDP crank case, not released just yet but not to far away I think, sounds like a good engine.

Part of what was on the WERKS NZ FB page,

"Enter the GO Champion 5 Port .21 race engine from GO Engine Co.
GO have re-introduced the GX5R 5+2 port sleeve and crank into an upgraded crankcase and cooling head design in the Champion."