Chivas,
You might check the distance from tank to carb that your fuel line travels, and how low the tank sets in relation to carb. Tank top should be about 1/4" above carb center line (more or less). Line from tank to carb should be as short as you can get it. Either or both of these items can cause a fuel draw problem. This results in engine starving for fuel, heating up, then quitting, unpredictably (20' high with 20' of runway left).

Steve