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Thread: Fuel Filler Cap Vent '86 K75T

  1. #1
    Registered User bvinson44's Avatar
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    Question Fuel Filler Cap Vent '86 K75T

    I suspect the vent for the filler cap on my K75 is clogged. How do I go about cleaning it? Do I have to remove and disassemble the filler cap?

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    MOA #24991 Pauls1150's Avatar
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    High-pressure compressed air from a small schnozzle oughta do it; if there's actual stuff in the hose, carb cleaner should soften or flush it. I don't know if the hose will stand up to brake cleaner, but may be worth a try. Also make sure it isn't just kinked somewhere along the run, or maybe a ty-wrap is strangling it.

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    3 Red Bricks
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    First, please read: http://www.bmwmoa.org/forum/showthre...r-thread-title!
    I've added that info. for you.


    Second:
    Quote Originally Posted by bvinson44 View Post
    I suspect the vent for the filler cap on my K75 is clogged. How do I go about cleaning it? Do I have to remove and disassemble the filler cap?
    The vent is NOT in the cap. There are two nipples underneath the tank about 8" forward of the right rear corner. The rear of the two is the rain drain for the filler cap area. The forward one is the tank vent.

    These will be plumbed in one of two ways:

    1. The preferred way: There will be a black plastic "cup" clipped to the frame below the nipples so that they drain into it. There will be a hose attached to the bottom of the "cup" that empties down behind the right peg plate.


    2. The other way: There will be a hose that connects directly to each of the two nipples. The rear one runs to behind the right peg plate to the ground. The front one (tank vent) runs forward (through a valve) into the crankcase (why it is not the preferred way) at the front top of the engine block. If the preferred way is used, the nipple at the top of the block MUST be capped so as not to create a vacuum leak.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
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    MOA #24991 Pauls1150's Avatar
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    Thanks, Lee!
    Paul S

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    Registered User bvinson44's Avatar
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    Fuel Filler Cap Vent '86 K75Tt

    Thanks for the "nag", for correcting the title of my inquiry, and for the very important information.

    I'm still not clear about how to make sure the hose is clear. Do I disconnect it and blow compressed air back toward the inside of the tank? I think it will be fairly easy to make sure the line is clear from the tank to the cup and out. Is there a standard procedure for doing all this? Is there a chemical that would be preferred? Does the cup need to be cleaned also?

    This is my first BMW and there's no dealer available here now. Thanks for your patience.

  6. #6
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    If it has the cup, there are no hoses connected to the tank nipples. They are open to the air and just drip into the cup.

    If it has the "less preferred" plumbing, then there is a hose connected to the tank vent nipple. The valve in the hose allows a VERY VERY small amount of air to pass in either direction.

    Either way, you can blow in to the tank vent nipple to determine if the vent is clear.



    Why do you think the vent is plugged? Do you here a whoosh when you open the cap?



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  7. #7
    Registered User bvinson44's Avatar
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    Fuel Filler Cap Vent 86 K75T

    Lee,

    Thanks for sticking with me on this. I suspect the vent is clogged because occasionally while riding at speed (65 - 70 mph) the engine will act like it's running out of gas. After a few seconds it will pick up and start running again. I spoke with a friend of mine who has a long history with BMWs and he said it might be the tank vent is stopped up.

    Thanks,

    Billy

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    3 Red Bricks
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    Possible, but not the most likely. When was the last time you changed the fuel filter?



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

  9. #9
    Registered User bvinson44's Avatar
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    Fuel Filler Cap Vent 86K75t

    Lee,

    I think it was changed about 3 years ago when I had to have a new fuel pump installed. I don't ride the bike very much because it's my second bike, so probably 2,000 miles ago. I switched to no ethanol gas about a year ago, and it was shortly after that I started having this intermittent problem.

    Billy

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