While out on a ride, the dime sized rubber coated metal plug blew out of the cylinder head of my 2003 WR450. It is recessed into the head just above the header. I can't get my head around what purpose this plug serves. My dealer wasn't able to offer any thoughts (which is a little disturbing). I am replacing the plug with a new one, but have to ask why the original blew out in the first place, and what the hell does it do?