GaryM and JBrannon go back and read my previous post on this problem, I don't have this problem any more. It is mixture as DA has stated and if you will get the break in done and set the low mixture as lean as you can get it all will be well.also I have had the needles change at high speed from vibration, all it takes is a spot and I mean a spot of blue locktite on the needles to tighten them up so they wont move. when they move they move RICH. good luck, these things really purr when broken in. Rick