I am nearing the end of my second gallon of fuel on my raptor 50 with the OS 50 Hyper engine. Everything was running well at the end of my last three flights a week ago. I've been hovering about 1600 RPM (measured with optical tach) with 5 degrees of pitch (pitch gauge), mid stick with about 45% throttle. I have still been running a little rich and I can hold my finger on the back of the crank case with no discomfort.

Today when I fired it up (hadn't changed anything). I couldn't get 1600 RPM at mid stick (only got about 1400 RPM) and I had to lean high speed mixture a little over 1/4 turn from where it was to get the same 1600 RPM and hover at mid stick. It is running hotter now. I can hold my finger for 3-5 seconds on back of crank case just after spooling down and still at idle after hovering for a full tank of fuel.

Is this normal? Why would I all of a sudden have to lean things out by a little over 1/4 turn to get the same performance?

Any ideas?

Well I guess I lost everyone on this question. But I found the problem. Bad plug. I probably should have checked that right off.