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Thread: 98 R1100RT tank vent plugged?

  1. #1
    It's a way of life! oldnslow's Avatar
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    98 R1100RT tank vent plugged?

    I have the classic symptoms of a clogged tank vent. The bike dies sometimes or idles poorly, and the very loud 'woosh' when I open the tank filler cap. Fuel actually sprayed out on one occasion. If the cap is open, the bike will idle just fine.

    How do I clear the vent line, and where/which one is it?
    Mike Davis
    "Old n Slow" It's a way of life!
    1985 K100RT

    1998 R1100RT

  2. #2
    Day Dreaming ... happy wanderer's Avatar
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    When you pull off the right side fairing there are two rubber lines cable tied to the frame coming from under the tank and next to the airbox. There are in line connectors on each one allowing the tank to be removed while the bottom section of each line is still on the bike.

    One is the tank vent and the other is the overflow from the gas cap rim. Blow some compressed air down the overflow hole in the gas cap rim to figure out which is which.

    Mark the line on the tank side once you know which is which and you can trace it to the fuel filter and pump assembly plate. If you are lucky the blockage is below the connectors where they disconnect next to the air box. If not the tank may have to be removed to clear the blockage or if the line is collapsed.
    MJM - BeeCeeBeemers Motorcycle Club Vancouver B.C.
    '81 R80G/S, '82 R100RS, '00 R1100RT

  3. #3
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    [





    QUOTE=Happy Wanderer;829500]When you pull off the right side fairing there are two rubber lines cable tied to the frame coming from under the tank and next to the airbox. There are in line connectors on each one allowing the tank to be removed while the bottom section of each line is still on the bike.

    One is the tank vent and the other is the overflow from the gas cap rim. Blow some compressed air down the overflow hole in the gas cap rim to figure out which is which.

    Mark the line on the tank side once you know which is which and you can trace it to the fuel filter and pump assembly plate. If you are lucky the blockage is below the connectors where they disconnect next to the air box. If not the tank may have to be removed to clear the blockage or if the line is collapsed.[/QUOTE]


    Should the other line be free also and what does it connect too? Thanks

  4. #4
    Rally Rat
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    Two small lines lines come from the tank. One is from the little hole you see when you open the fuel cap. It drains directly to the atmosphere by your right foot. The other line goes to a solenoid on the left side of the bike, then to the evap canister on the right side of your bike by the rear seat, then to the atmosphere by your right foot. I say "should" because a lot of folks to a canisterectomy, which removes the canister.

    If you still have a canister, it is proably clogged. That will cause symptoms like you describe. I recommend you do a canisterectomy to se if that fixes your problems. You can blow some air in the lines while you're doing it to see if any of them are clogged. You can google canisterectomy to find the procedures. There is a good one at ibmwr.org.

  5. #5
    Registered User rxcrider's Avatar
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    Almost right - a little clarification and a correction:

    Quote Originally Posted by JimMoore View Post
    Two small lines lines come from the tank. One is from the little hole you see when you open the fuel cap. It drains directly to the atmosphere by your right foot.
    This is the water drain. It allows water that gets around the cap to drain out, rather than going in the tank when you open the cap.

    Quote Originally Posted by JimMoore View Post
    The other line goes to a solenoid on the left side of the bike, then to the evap canister on the right side of your bike by the rear seat, then to the atmosphere by your right foot. I say "should" because a lot of folks to a canisterectomy, which removes the canister.
    The other line is the tank vent. It routes directly to the carbon canister. There are two other lines attached to the carbon canister. One is the atmospheric vent which terminates near the right foot peg, next to the water drain. This allows the tank to breathe through the carbon canister. As it does so, fuel vapor is trapped in the charcoal, reducing evaporative hydrocarbon emissions. The third hose from the carbon canister is the purge line. It goes to the soenoid on the left side of the frame. The hose then goes from the solenoid and splits in two with one hose going to the fitting on the bottom of each throttle body. With the engine running, when the solenoid opens, air is pulled through the atmospheric vent line, through the charcoal in the carbon canister and into the combustion chambers. This pulls the fuel vapor out of the charcoal and burns it rather than releasing unburned hydrocarbons into the atmosphere. The purge needs to be done to prevent the charcoal from becoming saturated.

    Quote Originally Posted by JimMoore View Post
    If you still have a canister, it is proably clogged. That will cause symptoms like you describe. I recommend you do a canisterectomy to se if that fixes your problems. You can blow some air in the lines while you're doing it to see if any of them are clogged. You can google canisterectomy to find the procedures. There is a good one at ibmwr.org.
    Trace the two small hoses from the tank and see which one goes to the carbon canister. disconnect that one from the carbon canister to see if it solves the problem. Put a cap over the nipple on the carbon canister and disconnect the electrical plug from the solenoid on the left side to prevent any unfiltered air from being sucked in. If you have a mighty vac, use it to suck on the vent hose you disconnected from the carbon canister. If there is an obstruction in this hose, you don't want to blow it back into the tank. If you find wet fuel in this hose, you may have a split in the line inside the fuel tank. When this happens, it can wet the charcoal, causing the vacuum in the tank.

    Be careful using compressed air to blow through either the vent line or the drain line. They are small relative to an air compressor hose and if you try to flow too much air through them, they can rupture inside the tank where they have been deteriorating slowly from sitting in fuel. If there is a clog in a line, it can rupture even more easily or it may blow the debris out somewhere you don't want it if you manage to clear the clog. Applying a vacuum to the exit end of the vent or water drain hose is a safer bet.

  6. #6
    Rally Rat
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    Good points. Thanks. I hadn't seen one in awhile. My canister hit the trash can in 1997.

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