Originally Posted by DolphinJohn
Griz, there seems to be a slight difference between the two threads about the hoses.
10cup, in the F800riders.org thread, thinks the long line to the tank is an intake, and he put a small filter on it to keep dust/debris out.
Crazy mike in his post here on ADV thinks that hose is the drain hose, and he left it hanging at the bottom of the bike.
You seem to be pretty good at this kind of thing, and have all of the diagrams, so what say you?
I noticed this difference as well, and am a little stumped myself. The parts in question are #3 and #'s 18-24 in diagram below. On one hand, it makes sense that if the fuel pump is pumping fuel out then the tank would need to draw air in. Is that the spot though? But it would also make sense that it's a safety valve for the tank, in which any excess fual or gases would vent out there. The test would be to carfully check the valve (#21) to which way it flows.
I'm leaning more towards the mentality that things go out
through there. This would make sense in the canister design as well, since the canister needs to get the excess gases fed to it from the tank. This seems like the spot. I think I'm just going to let mine dangle, given the BMW parts diagram calls #21 a "Ventilation Valve."