i am amazed how much better this machine works without the big bore kit...I do not know why anyone would put a big bore kit in for... I bought mine from my brother, he put a big bore kit in fall of 07 road it that winter no problems. Fall of 08 i buy it from him... being of december go to blue river first day it was good running good no problems.... second day got to the top of the mountain and the motor blows --- had to put brand new motor put in... piston skirt broke off and well the end