Originally Posted by the_gr8t_waldo
post9-are you quite sure that's a vent? forgive me for asking, but to my limited experence, it looks like a drain for sloppy fueling/rain water. i have wrestled with aug tank problems too, in my case a st1100 with a sampson aux. fender type tank-got it used with NO Installation instructions. the problem sounds like what i had. the cause in my case was that the fuel pump raised the pressure in the tank, and forced fuel out the aux fuel tank vent line.(fist go round it was ventedto the air right above the r. tire. and for a 1/8 inch line, it delevered an alarming amount of fuel to my rear tire) the fix for me was to reroute the sub's vent line into the main, and at the highest point on the main.
You are correct it wasn't a vent it was a drain for fuel spills. I hadn't thought about rain water though. Doh! I repurposed it for the vent for the subtank, and it seemed like a convenient spot for it.
I thought there must be a check valve of some kind that would allow air to pas but not fuel and put it in the line.
Anyways if I'm going to keep that line as a vent I will ned to be careful about water getting in there.