Very good information above including the videos!! Helping and showing racers how to check things like this is what we all need to do to keep racers at the track. Knowing how to check the valve lash is important as if a racer wanted to or told to would know how. THANKS guys for this!!! One VERY IMPORTANT thing that hasn't been mentioned. Rather you are just firing it up for a few minutes or just coming off the track, once you kill the motor BE SURE TO PULL THE ROPE UNTIL IT COMES ON COMPRESSION!! This seals the valves to the valve seats. Last thing you want is valve leakage and/or warpage.