When you're breaking in an engine with an extremely rich carburetor setting, you need to leave the glow igniter on the motor (otherwise it will stall). It sounds like you're extremely rich and can lean in your needle settings a little. Remember to pay attention to your engine temperatures during break-in. You don't want to run to cold or too hot. I try and stay between 140 and 200 degrees farenheit (others will have different opinions on appropriate temps for break-in but this has worked well for me on over 40 of my engines and counting).