Hi, Thought I'd pass on this simple fix. Last flying season I started having problems with my fast idle. At about 2700 rpms my engine would surge up in rpms then back down to about 2000 rpms continuosly. I read of a plunger replacement here on RCU and decided to just fly some of my other planes and put this one away for awhile. Thinking I needed a new plunger I called Richard at YS Performance and explained my problem. He said it sounded like my idle screw was set to lean. He suggested to richen it up by screwing in the idle screw. I arbitrarily screwed it in 1/2 turn and today I went to fire it up. It runs flawlessly!! Perfect transition from 2200 to about 9300 rpms. It will idle forever without surging or lagging. Transition to full throttle is instantaneous. My YS 110 is BACK!!