sounds like a air leake problem to me. I would start by checking the pin O-rings,( look for a cracked O-Ring) then place a piece of fuel tubing on the fuel nipple and brush some soapy water around all attachment points on the engine. Look for bubbles. You can also by a soapy mixture for plumbers that run gas lines in the house. It come in a small spray bottle. Then re-seal the area that you find bubbles. Then reset your engine to the factory presets and start the tunning again. I bet it is simple like the cooling head bolt is loose or the carb needs to be re-seated.