I went for a ride today and when I stopped and took my helmet off I heard a hissing noise. It was coming from the tank lid when I opened it, it stopped but when I shut it again it started to do it again. So that leads me to believe its not the tank itself under vacuum but perhaps the hose that comes up to meet with the small hole in the cap itself? The tank was recently painted and I put in new filters and new hoses when I reassembled it. What could be going on? Or has it always done this and I just never noticed before. Or is something plugged up and not breathing properly. Its an 01 S4 Monster. Thanks
It's normal.
The fuel expands/vaporizes when warm and causes the vent in the cap, a little rubber flap to vibrate.
My 2001 monster dark does this as well. Although I would describe it as more of a moan. Since its dark and it cries I call it emo.
I'm glad to hear that its normal, just weird that Ive never noticed it before. I stopped worrying about it already. Thanks guys