My buddy has a 58 panhead. Whenever it's hot out gas just pushes out of the gas caps. It did it today and both tanks were only half full. We tried a left vented, a right vented cap, both caps vented and neither caps vented. Does anyone have any ideas to stop this from happening? This has been going on for years. The emblems are ruined and the paint on the tanks is ruined. Sometimes the left tank gushes, sometimes the right tank gushes. If you take the caps off it starts to level itself off.