What jets are in the bike. What clip position is the needle on. Where is the fuel screw set. You said that it ran fine for 40 min before giving you trouble. Maybe its jetted rich and is killing the plug over time. So we need to know what the folowing jets are: main jet __ main air jet__ Pilot jet__ Pilot air jet__ Starter jet__ needle #__ Needle clip position__ Fuel screw position (turns out)__ DOH NEVER MIND :cry: Oh, and I'm running all stock jets and the needle at position/groove #3 (from the top - 1 groove leaner).