Well I got a 35 Pilot Jet from a friend and it seems to have cured my rich fuel problem. But I need a hotter plug for slow riding on the farm. Champion suggests for average riding a RN4YC. The nearest I have in the shop is a RN9YC. Is that plug too hot for the Trail Boss 4X4 250CC. I don't want to ruin it after all the work I have done on it. Thanks a lot for all the info you gave. Jay