So you even have to Bore the Block out for the 50cc? Also for the 65? We want to stay at 50cc because the ZA50G fits Cylinders with more than 38mm of Bore, but not Pistons of more than maybe 40~41mm. Might just go for a 1KW Supermaxi Cylinder and Head, they already do 45 with a 12mm Bing and Normal Exhaust.