Well, you would be getting more cooling air over the fins under those conditions. But your motor is sucking down fuel the hardest and generating the most heat when you are under sustained heavy load. So there is a difference between getting fuel through the line and getting enough fuel/oil for sustained high speed running.
Check to make sure the screen in the pet*c*o*c*k is clean. Make certain the fuel tank breather is unobstructed. If you are running an in-line fuel filter, remove it or replace it. And make sure your carb's float level is not too low. While checking the float level, make certain there is nothing obstructing the main jet.
If those things don't help, you might want to go up slightly on your main jet or add more oil to your mix so that things are better lubricated.