Before you start turning the needles on the carb, you need to make sure the throttle is closing completely when you let off the trigger.
In order to keep the engine running consistently you need to keep the temperature of the engine consistent as well especially for break in. Engine needs to be preheated to 180-200 degrees with a heat gun or engine heater before you start it and then keep it running in the 180 to 230 degree range for the rest of the break in period. If you can't keep the temps up, you can wrap some foil around the lower fins of the cooling head to help keep the heat in.
Hope this helps.