I had exactly what you are describing once after a carburetor rebuild. Talk on the email list - back then - suggested they may have sent the wrong float needles with the rebuild kit. I replaced the new ones with the original ones and back to the way it was for another 500 hours. Apparently the rubber tips on the needles come in various hardness and the new ones were not correctly mated to my engine. Sorry, I can't help with which is which - too tlong ago.