Ok, I'm stumped and need some help.

I've got an Evolution 26 in a H9 Mustang that has over 100 flights on it. Engine has run like a top and has plenty of power for the airplane with an APC 16x8. It's got an Evolution wraparound muffler and I've been using about 5oz of oil per gallon (twentysomething : 1 ratio)

About 2 months ago after over 100 great flights on it with no problems, it flames out on takeoff....but that's not my problem.

I proceed to check the fuel system out completely, and ended up rebuilding the tank to make sure there were no problems. I also cleaned out the carb and double checked the fuel passages and gaskets/diaphram. I had to change the spark plug because the other one broke off. I don't know what the gap is set to. I put it back together, and now it runs like a top again.....but......and here's where I'm stumped....it now seems to get hot after a few minutes in the air and starts surging/quitting. I proceed to rebuild the carb with all new gaskets/diaphrams, and even a new thermal spacer between the carb mount adapter and the carb body. Still the same problem. I can richen it up and make it slobbering rich and fly it around and it still gets hot. I don't think the engine is seizing up, I think the carb is just getting so hot that the fuel/gas is starting to boil. When I land, I can't even touch the carb it is so hot.

What would make this engine start acting like this after so many troublefree flights. Again, it runs perfectly for the first few minutes while it's cool, then the heat starts to soak into the carb and it goes south. Cooling air opening for the engine is right in front of the carb and it blasts right on it before it gets to the cylinder, then the muffler. Could a bearing be going away and causing the excess heat? The engine feels beautiful when you turn it over and will do a nearly impossible tick over idle when cool. Could an improper gap on the sparkplug cause excess heat? Maybe a bad batch of gas?

Anybody have any ideas? I've even replaced the ignition to eliminate that possibility.

Help!
KMac