Hesky, The higher RPM creates more heat due to the greater freaquency of combustion cycles NOT more friction! If you have friction between your piston and liner, your engine is about to seize. The piston should be seperated from the liner by a layer of oil. Some friction is present due to oil shear, but if there is actual contact between the piston and sleave, you have serious problems. As previously mentioned, too much load will also increase operating temp. As suggested, gear for track & try other routes to bring temp down. Increasing nitro can also bring temps down. This results from greater power outputs at richer settings.