my glow starter has a gauge on it to tell me my glow plug is bad. The engine runs so rich for the first few tanks that it could be a glow plug that's the first thing I check. The top of the piston will tell you if you over heated it and look on the skirt of the pistons from the exhust port that will let you know if the piston is loose. I have about 3 gallons on mine and runs great and replaced the glow plug 4 or 5 times.