I'll try richening the low end. Indeed it doesn't sound right when I richen the low end but I'll try it. I think it just isn't getting a constant fuel supply at idle. I'm running a MA 14x6 prop on it. I probably have clearance for a 15x4W but the blade seems wide enough on the MA. One time I ran a YS120 on just a Perry pump and it ran flawlessly, although I was not hovering with it. It's a bolt on affair, it can't hurt to try it. -Tom