you'll want to heat cycle the engine with the first tank of fuel. Meaning, bring it up to temp (180-200) and then shut it down, drop the piston to bottom dead center and let cool. If you have trouble getting the temp up you can wrap some aluminum foil around the head. What you DON'T want to do is lean it out to get the temp up. Leaning it out new during break-in can ruin the engine real quick. Cycle it like that 3-4 times then you can start driving it around a few tanks. After about 3-4 tanks you should be able to start leaning it out and bring it up to speed.
hope this helps