Odd Occurance under Fuel Tank

Had a rather odd thing happen today, figured I would see if anyone else had. Did a search and didn't find anything so I'll post a new one. I took the bike out today for a short trip down to the mall to pickup a phone case. Didn't push it hard on the way down, temp was about 73, tank at 3/4. Ran fine all the way down. Parked it and came back out about 35 min later. Started it up and had some odd humming coming from somewhere under the tank. It continued no matter if I killed the engine, turned of and removed the key, etc. Just stopped on it's own. Restarted the bike twice, same thing. Didn't seem to effect the engine or fuel flow. Got it home, could not get it to do it again. Ok so what the devil was it? Bike runs just fine and I could see no fuel leaking or anything.

 

Electric fuel pump maybe. Turn ignition on without starting. You should hear the pump priming the lines. If it is suddenly louder, you could be looking at the need for fuel pump repairs/replacement.

 

Was it more like a whirring? Fan maybe, like some cars that keep running? Engines can have "heatsoak" where heat from running increases after shutting down. After starting it, hot water circulated and tripped thermal switch for fan. I now see the opposite, after installing a manual over ride on my fan. I will park, turn off engine and let fan run, but temp does drop much until I restart and cooler water circulates, then it drops drastically.

Or the fuel pump as noted.