For me, this little valve is the smoking gun. I experienced the water-uptake through the original non-T'd vent hose, A second vent in the manner of the BMW recall fixed that. The issue I still have on occasion that I suspect may be caused by this little valve is that a huge amount of pressure can sometimes build in the tank. At one point I opened a recently filled tank and fuel exploded out all over me. What I suspect is that sometimes a bit of fuel reaches that check valve and stops it up, then the pressure that builds inside the tank can be really serious. Erling's experiments suggest to me that it might be good to arrange for that little valve to point up somehow, so it is 'self bailing'. I've played with it my self and it is really picky, it locks up solid very easily. I've previously thought about just removing it all together. Why would you ever WANT 5psi in your fuel tank, especially if it's an entirely variable parameter? If it were removed though, the tip-over valve would be the only defense against liquid fuel reaching the CC, so it'd probably be better to help the valve work the way it was intended. we've seen that the valve is the same on the Euro bikes, the only difference is the presence or absence of the CC. I wonder though if the hose that carries that check valve lies differently on the euro bikes, since it's running to the bottom of the bike rather than to the CC? from what I remember, (and I can't look at my bike right now), it doesn't seem like it should be any different, but maybe?