It probably dont gets enough fuel. The starter will work like a fuelpump. when you crank the engine with the starter it will suck fuel from the tank and reach the carb. And when you turn off the starter it wont suck fuel anymore. So, turn the full speed needle completely in, and then out again about 2-2,5 turns. If the problem still occurs then I dont know. I had a similiar problem once. You should also check the fueltank and the fueltubes for leaks, and clean the carb.