Gas Tank Vent Hose Question

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by Edder B, Nov 5, 2012.

  1. Edder B

    Edder B Meister Poser

    Joined:
    Feb 25, 2002
    Oddometer:
    376
    Location:
    Cincinnati, Ohio
    I again took off my left side gas tank to replace the seals in the fuel pump. I bought the bike used and both times that I have removed the tank there is a vent hose that I have no clue where it goes. There are three vent hoses, one on the top that routes into the upper fairing, one in the middle of the tank and the third towards the bottom, which attaches to the cross over. Its the middle vent hose that I have no idea where it goes. When I took the tank off the first time it was just routed up towards the glove box and had a crimp in it. I also have to add that when I first got the bike it had a hesitation at around 5K rpm. When I put the bike back together I routed the hose down below the frame. The hesitation went away but then when I filled the tank up I got gas gushing out of the hose. So I routed it up and crimped it again with a zip tie. That kept the gas from coming out but the hesitation started back up. I do notice that on the end of the hose it looks like it, at one time, attached to something. So this time I routed the hose up again along the frame towards the glove box. So far no gas is leaking and the hestitation is gone again.
    So my question is, does anyone know where this, the middle vent hose, is suppose to go? Is OK where I have it now?
    Thanks for any help.
    #1
  2. Johnf3

    Johnf3 Long timer

    Joined:
    Apr 10, 2007
    Oddometer:
    1,140
    Location:
    West Texas
    It's not a vent hose, it is a drain hose. It drains the area surrounding your filler cap. If you had gas gushing out of it, you may need to slow down or aim better.
    #2
  3. fieldmechanic

    fieldmechanic n00b

    Joined:
    Sep 28, 2012
    Oddometer:
    4
    I am having a similar issue. I fill it nearly full of gas and park it and I come back to a puddle of gas under my bike. The middle hose is just routed straight down toward the skid plate. Where were these hoses originally routed? Or is there a better way to route it?

    I bought the bike a couple months ago and the previous owner had done all kinds of stuff to it... so still trying to figure this out without lighting my garage on fire.
    #3
  4. TheMuffinMan

    TheMuffinMan Forest Ranger Magnet

    Joined:
    Mar 31, 2010
    Oddometer:
    7,639
    Location:
    Pueblo, CO, USA
    If you fill up the bike you'll need to park it on the center stand until you burn off a gallon or so or else the gas from the right tank will drain into the lower left tank (when parked on the side stand) causing it to spill out.
    #4
  5. Head2Wind

    Head2Wind MotorcycleMayhem

    Joined:
    Mar 13, 2006
    Oddometer:
    2,662
    Location:
    NorthWet Washington
    upper vent mod like below will resolve most of the spill issues, however not all, especially after a 100% fill then park on side stand. As stated previously the middle of tank hose (the one with the 90 degree fitting) is only a filler neck/cap area drain. The hose should run straight down into the skid pan (both sides). The upper middle (if fitted) cross over goes tank to tank. The upper front (as pictured, MODIFIED, not stock) loops up into the highest point of the upper fairing then down all the way to the skid plate, both sides are setup this way. The bike pictured spent many a mile in hot and rough terrain ridden hard through that terrain and I never had major spillage or fuel delivery issues. Occasionally it would leave a little puddle of fuel, especially on a really hot day, after filling with fuel and parking it for lunch stop. Keep in mind that most fuel is at ground temperatures as it is pumped into the fuel cell, probably 50-60 degrees F during the summer depending on factors, but then the fuel cell is at 100 degrees F or higher. The fuel will begin expanding and the lights (propanes, butanes etc) will begin to flash off, and if they don't have a long vertical path to shed the liquid fuel that gets pushed out with them, the fuel cell will push out a significant amount of liquid fuel and the puddle will be large. If the venting system does not allow the fuel cells to purge easily, then pressure can build to the point where it will spray fuel out the filler caps and/or push fuel past the float needles (950).

    [​IMG]
    #5
  6. fieldmechanic

    fieldmechanic n00b

    Joined:
    Sep 28, 2012
    Oddometer:
    4
    The fuel seems to be coming from the middle tank hose appears to be where my fuel is coming from. The front vents have been routed to underneath the headlight, so its pretty easy to see if there is fuel dumping on the front fender/tire/brakes. I get a little leak from there every once and a while but nothing like the puddle from the center of the bike. It leaks less when the bike is laying on its side.

    The other weird thing is that when it leaks I pop open the 2 tanks and the right tank (uphill tank) is overflowing and the left (downhill tank) is low comparatively. It does not have the upper middle vent/crossover, that I have seen installed on some bikes. So the only place that they are seemingly connected is the lower fuel hose. So I am a little baffled by the whole thing.:eek1
    #6
  7. Head2Wind

    Head2Wind MotorcycleMayhem

    Joined:
    Mar 13, 2006
    Oddometer:
    2,662
    Location:
    NorthWet Washington
    Route the forward/upper vent as described and the issue will be solved as far as the imbalance. The leaking from the mid drain might be related to the fill cap seal or a failure of the tank somewhere inline with that drain. Failure of the tank would be very odd.
    #7