When you are breaking in an engine it needs to run rich and at 220 or higher use a heat gun and alum foil or an engine heater run it for 5 mins or so and then turn it off return the piston to bdc and let the engine cool all the way down. It usually takes 20-30 mins to cool then repeat. Personally I do this 5x then run it on the ground at 1/4-1/2 throttle with the head wrapped to keep the temps up 220+ a complete tank, let it cool and repeat. I do this until I have 6 tanks through it. Then I take it to the track and let it rip. Works for me. But you have to let it cool completely in-between cycles