Yesterday after parking my FJR on the sidestand in the garage after a hot ride in the high 80's I immediately opened the gas cap and left it open. A short time later I heard the tank gurgling and I looked down and saw significant bubbling in the tank.
As I came to a stop the fuel display showed two bars.
When I opened the cap I heard no pressure changes -- nothing rushing in or out of the tank.
As far as I know the venting system works fine. I'll occasionally see a damp spot below the vent hose after the bike has sat in the sun for an hour or so.
I'll repeat this "cap open" experiment during the next week or so and see what happens.
"Boiling Gasoline" sounds like impending doom, especially if it's between my thighs. Funny that I've never heard it from my gas tank. Have heard coolant bubbling after I shut off the bike, but that's normal for riding in temps above 90F.
Gen1's didn't have the foil pad like later Gen's did, so when you stop, heat off the engine will transfer to the tank..... some made up foil pads, surely it would help.
Gen I also had a fuel return from the fuel rail. After the gas absorbs the heat from the fuel rail it gets sent back to the heat exchanger gas tank. I wonder what the actual temperature is on the fuel return line.