I looked at your fuel and it only has 15% oil. That may not be the problem, but that is a little low. Adding some castor oil to bring it up to 18-20% would provide additional cooling.

Another question: what is your fuel tank setup? If you don't have enough muffler pressure or have too much line between your tank and engine, you might have a good tune with a full tank but go lean when the tank gets low.