it is located at the highest point but if the tank is overfilled and the fuel expands in the tank - which it does when it gets from the relative cool subsurface tanks to the higher temperature in the bike - the liquid fuel would reach the valve and shut it. Then overpressure would build up in the tank. The valve is only meant to let fuel vapor pass. But i think there were also cases where the valve was not functioning properly because the tiny steel ball was dislocated. That said, i don't know if the US models with the evap cannister work the same way.
The fuel tank valve is the same in the us. The only difference is the tank valve hose gets attached to the charcoal/evap canister instead of open air in order to collect the fuel vapor for later purging back into the throttle body to burn.
The valve is (obviously) located at a point higher than you can actually fill the fluid level to as it is in the Cap fitting. However, here in Philippines and other places the gasoline is stored in underground tanks and considerably cooler than ambient temperatures. So the bike got filled to the brim with relatively cool gasoline and was subsequently parked in 33-35 C air temperature, the tank temperature will go up even more if in sunshine due to the black colour. Expansion of the liquid takes place rapidly and to the point where the liquid level rises and closes off the vent valve, thereby creating internal pressure build up within the tank.
US models are the only ones with the Evap Cannister and they do have exactly the same Tank Vent Valve set up with ball washer and spring.
I only had about 2 gallons of fuel in my tank when it erupted through the fill, hole, so I assume I am one of the cases where the bit ball dislocated.
I received my first gas shower on Saturday Filled up in Woodland Park (no issues) on my way up thru Tarryall, Jefferson, then refilled in Bailey with about 1.5 gallons left in the tank. Pulled the gas cap and whoosh! Scared the SH*T out of me and now I'm considering ditching the valve. Gullywasher: did you remove yours? any issues since? advice?
Ditching the valve is a must do as far as I am concerned. There are no issues as it is only there to prevent fuel spillage if you drop the bike, something I do not plan to do of course.
Funny! We might have spewed gasoline at the same gas station! Maybe there is just something about Bailey? I removed the ball valve assembly - took hardly any time at all. No issues since then. I highly recommend you do this as well.
Gonna remove this evening... bike is starting to sputter once warmed up, doesn't do it when cool... After about an hour of riding today, I cautiously cracked the filler cap open and there was a lengthy hiss from pressurization... then put my ear to the opening of the tank and listened to her gurgle for a few minutes. Welp, guess this is part of joining the TR650 clan
You might also be sure that your little black hose is not pinched anywhere in the bodywork/interior of the bike. That has been the issue causing pressure in my fuel system once or twice.
