Happened to me too when I overfilled. Takes 5 minutes to fill up, too. HereĀ“s your tip of the month from personal experience. On a ride, for no apparent reason the top left surface of my 02 Spirit gas tank indented. Ping, and it looked like somebody dropped a bowling ball on the tank. Removed the gas cap at the next fill up and it popped back out about 80%. Tracked down the source of the problem: an insect had packed mud in the end of the vent tube. I cleaned the dirt out then neatly wrapped black fiberglass window screen material over the end of the tube and secured it with a small black zip tie. Lesson: screen the vent tube before your tank caves in from unvented suction.