I would go with the CRF. The speed is an excellent mill but OS engines dont have the greatest longevity. So I wouldnt spend $500 on an engine that you may get only 6 gallons at most out of. I even know anexpierenced guy who only got 4.5 gallons out of 1, and parts are outrageously riced for the speed. I have seen the CRF in action and it is a fast mill, not shure on pipes or plugs for it though.