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Thread: K1100LT fuel tank vent (?)

  1. #1
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    K1100LT fuel tank vent (?)

    My K1100LT has two pipes on the underside of the fuel tank. One is connected to a hose which, in turn, is connected to what appears to be a one-way valve. The other pipe is not connected to anything. I removed the tank without noting which pipe had the hose, so now I'm uncertain where to refit it.
    My old K100RS had vent hose(s) too, but it ran to a little reservoir under the right rear of the tank. My questions: what is the purpose of the two pipes on the K1100LT? Which pipe should the hose be connected to? Should there be a hose for both pipes?
    Thanks for the advice.

  2. #2
    Registered User GTRider's Avatar
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    One pipe drains the “water well”—the area underneath the filler cap and surrounding the filler neck, where rainwater or bike-washing water can pool and be drained away. The other hose is the tank vent and depending upon year/model of bike leads to either a crankcase breather or a SHED system incorporating a charcoal cannister. I’d have to look at the parts fiche to see which your bike has. At any rate, the tank vent, which should be connected to the hose & valve, is easy to identify. Open the fuel cap, attach a hose to one of the pipes and blow into it while feeling for air with a finger on the drain hole in the water well. When you identify which pipe connects to that, connect the OTHER pipe to your tube/valve.

    Your older K didn’t capture tank fumes, so both hoses on it simply vented/drained to atmosphere.

    HTH,
    DeVern
    DGerber
    1983 R80ST — 1984 R80 G/S-PD — 2004 K1200GT w/Hannigan S/C — 2010 K1300GT — 2018 R1200GS
    BMWMOA#52184, AMA#271542, IBA#138

  3. #3
    3 Red Bricks
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    Walt,

    The forward tube is the tank vent.

    The rear tube is the rain drain.

    Easy way to remember is; forward tube hose runs forward to check valve and engine. Rear tube connects to hose that runs to the rear and drains near the peg plate.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  4. #4
    Quote Originally Posted by 98lee View Post
    Walt,

    The forward tube is the tank vent.

    The rear tube is the rain drain.

    Easy way to remember is; forward tube hose runs forward to check valve and engine. Rear tube connects to hose that runs to the rear and drains near the peg plate.

    Lee, is this the same routing of the vent to the crankcase that my dealer disconnected on my K75 at the 600 mile service because it was known to be able to dump raw fuel directly into the engine oil?
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  5. #5
    3 Red Bricks
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    Quote Originally Posted by PGlaves View Post
    Lee, is this the same routing of the vent to the crankcase that my dealer disconnected on my K75 at the 600 mile service because it was known to be able to dump raw fuel directly into the engine oil?
    Yes. That is the way that most bikes sent to the US were vented. Not familiar exactly where the tank vent hose teminates on the K11, but the tanks are the same.

    I change every K75 that I work on over to "the cup", which is how most non US bikes were vented. It not only eliminates the possibility of raw fuel and vapors entering the crankcase, but it also makes removing the fuel tank or shifting the tank to access the radiator cap much easier. It also prevents the tank vent hose from getting kinked and causeing problems. Plus, the cup (air accumulator) currently only costs $5.32 and you use the existing rain drain hose as the cups drain hose.

    Your dealer did you a favor.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  6. #6
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    K1100LT tank vent

    Got it. Thanks.

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