This past couple of weeks my bike has developed a weird coolant issue. After a ride out I get home and in the time it takes me to get out of my leathers a puddle of coolant about 12 inches in diameter appears under the bike. It's coming from the overflow pipe. Weird thing is this has happened about 6 times now and the coolant level hasn't dropped. It wasn't overfilled before. It sits just under half way up the expansion tank. Usually the only way a bike can "make coolant fluid" is if the head gasket leaks and oil is introduced to the water causing the level to rise.My head gasket seems fine. Maybe I have a coolant fairy filling it up when my backs turned. Any ideas?