after going on a 40 mile ride i noticed my tank was nearly empty after filling it up prior. not thinking too much about it i filled it up again and when it got to the top as i was stopping the pour i noticed gas leaking out the bottom of my quad. i tried it again with a little more. nothing. then when topping it off when it was right at the point of spilling over i saw the gas coming from the bottom of my quad again. I then noticed the gas gong through the little line coming off the top of the tank and it goes up off to the front of the tank somewhere. so this time i clamped that line and filled it to the top again and the loss of fuel stopped. no more leaking from underneath. next day i went for another ride and it appears that solved the problem but i have some concerns.
1) after this ride upon opening my gas cap i heard a big rush of air/ loss of pressure.
2) where does that line on the top of my tank go? I'm assuming it came unattached somewhere down the line.
3)Is there any potential problems keeping that line tied off?

thaksfor any input/replies....

 

That's your tank vent. Gas shouldn't going out it unless the fuel expansion after filling causes gas to be pushed out. If you leave it clamped off you'll eventually get a vacuum lock in your tank and fuel won't get to the carb. The hose usually just ends somewhere down near the bottom of the frame.

 

so the gas im seeing after filling is a normal function and i shouldn't just fill it that much anymore?

I assumed while i was riding the fuel was being pushed out from the turbulent terrain. perhaps thats not the reason im seemingly losing gas. I did notice the fuel gauge no longer works and i can see the floater moving around in the tank.

 

You may have to remove the tank cover plastic,but make sure the tank vent line is routed to the steering post area and hasn't dropped down. All this does is allow gas to flow out on the ground when the tank is full or close to it. Best to have the vent line routed down into the steering post and you wont have this problem. Plus on newer models some have one way check valves in the line that may have fallen off.Just depends on what year model your 400 is.