That is a very common occurrence. In fact that whole overflow system relies on no blockages at all otherwise you can end up miles from no where with no idea what's going on.
The obvious conclusion when the bike starts after a few minutes is that this is the problem. I was in the boon docks when the over flow valve seized.
Luckilly for me I had learnt the symptoms from this website and just disconnected the rubber line from the tank.
I have since bought a breathable fuel cap and re-installed the overflow valve after fixing it. Not sure what'll happen if I do go over but hopefully that won't happen ever - touch wood
