I was having problems with some of my engines that have been run for a while. THey were tuned rich but running way too hot. I ended up ripping the engine apart and cleaning it real good insluding polishing all the internal parts. Last I changed the front bearings in the engines and they ran like they were new again. Tons of power and under 230 degree's. I think you have a bad airleak and I bet it will be the front bearing. I will be changing mine every year from now on.