The advice above is excellent. Mine was a bit contrary at first but once broken in it runs great. It doesn't make as much power on 15% but does seem to run smoother especially at idle. I would check for an obstruction in the needle valve assy as rcdude mentioned. I have had to completely disassemble the carb to get mine cleared before. Sometimes the little piece of trash doesn't want to wash out any other way and if it fires and then instantly dies that's a strong possibility. The other possibility is the fuel tank is too low. If the fuel drains back out of the line after the initial prime the tank may be too low causing the engine to die before the fuel makes it back up to the carb. Good luck.