Haven't done that (YET!), but you touch on an interest I have involving the cap. I noticed that after running the MUTT for awhile and shutting down, I can hear a very faint squeal/hiss that I tracked down to the fuel cap. My question is "Is the cap vented?" Does the system vent elsewhere? If so, where? I crack the cap open and can hear a definite release of light air pressure. I know this isn't normal.