There are lots and lots of threads on this one. A serch will bring in tons of them. Basicly you need to run it very rich for a good while. Maybe 6 tanks or so. Keep the rpm's down to half throttle or so for the first 3 or 4 tanks. After 6 tanks or so start leaning just a little each tank full. At around 12 tanks or so you should be ready to go. I know this sounds like a lot. but the rings on these engines is small and kinda delicate. They have to be gently broken in. Once broken in properly with a little care they will last a very long time. Good luck with your new engine.

Mark Shuman