Thanks for the reply. I've actually got it running well now. I fly off asphalt, but the starting area is on the grass. I pulled the engine out of the plane and tore it down. There were little bits of grass all over it and some inside the carb. I found the air chamber and carb screws were only snug. I cleaned all of that up, cleaned out the regulator, checked valve clearance and tightened everything up. I found that I had my low end screw 3 turns out which was probably at least partly to blame for my problem. It would idle fine without climbing rpm's but I guess it was too lean. Based on all I had read about YS in general, I thought the low end screw had no affect above 1/4 throttle. I then read something about the 115S low end screw affects up to 3/4 throttle. I'm not sure what to believe, but obviously it's more critical to overall performance than just a reliable idle.