After riding last weekend for a couple hours, I got back to the parking area, and I could hear the fuel boiling. I slowly screwed the cap off a little and the pressure was intense. If I would have taken off the cap fuel would have been everywhere. Could this be a bad cap maybe a vent tube plugged?

Thank for your help...

 

Bad vent tube yes, bad cap no. Not sure why it would be boiling though ?

 

check the vent lines for sure. maybe the pressure was making the gas bubble??