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Thread: 85 K100RT vent hose question

  1. #1
    Registered User 58058D's Avatar
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    Yep, originally that check valve would squeal when pressure in the section coming from the tank was enough to push through it.....that alone was enough to want it removed. But the idea of fuel being dumped into the crank was not much appreciated. Many of us did the reroute before BMW made the recommendation. I simply put an appropriate sized screw in the lower tube section after shortening it, and rerouted the other end aft....If your old tube is really brittle, you may wish to replace it with a short section of new that is closed off just to avoid the unlikely event of contamination.
    Jim Douglas '00 K1200RS >135,000 miles my primary bike again,
    Gone: '09 K1300S sold @ 22k mi, '93 K1100RS traded @ 78k mi, '85 K100RS sold @ 44k mi
    '06 Kaw 650R track bike sold
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    sorry to revive an old thread. So on my 1985 K100RS, I see the 2 outlets on the right side connected to nothing. I couldn't see a plug there either. I do see the relief valve sitting on top of the engine crankcase connected otherwsie to nothing. So i take it, there is nothing to do?

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    Quote Originally Posted by cy7878 View Post
    sorry to revive an old thread. So on my 1985 K100RS, I see the 2 outlets on the right side connected to nothing. I couldn't see a plug there either. I do see the relief valve sitting on top of the engine crankcase connected otherwsie to nothing. So i take it, there is nothing to do?
    The front pipe may drip fuel. You can get a catch can from BMW to funnel the fuel to the foot peg area. When I used the can I got a fuel smell on hot days, so I run a hose from the front pipe to the peg area. The rear pipe only drains water from the cap perimeter.
    Ron

    91 K75RT ABS

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    thanks Ron for the reply. I do have a catch hanging on the right rear corner. When I don't see the metal tube coming off the tank lining up to the opening. Is there a rubber hose that guides it from the tank into the catch?

  5. #5
    Registered User 58058D's Avatar
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    I am guessing the catch can is a prior owner addition. I would suggest that you need to add a hose from the correct 'nipple' and run it either to the catch can or just out near the peg/centerstand. Just hanging free below the pegs is better to avoid the fuel smell mentioned with the catch can. Back then, I did not know the catch can was available and as I mentioned above, I just had mine hanging free out by the center stand as later models came that way. But you seriously do not want any potential drips to be able to land on hot parts. I would also remove the pressure valve and just plug that line down there going to the crank case, just to be safe.
    Jim Douglas '00 K1200RS >135,000 miles my primary bike again,
    Gone: '09 K1300S sold @ 22k mi, '93 K1100RS traded @ 78k mi, '85 K100RS sold @ 44k mi
    '06 Kaw 650R track bike sold
    http://www.seagullbb.com/

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    Quote Originally Posted by cy7878 View Post
    thanks Ron for the reply. I do have a catch hanging on the right rear corner. When I don't see the metal tube coming off the tank lining up to the opening. Is there a rubber hose that guides it from the tank into the catch?
    The tubes line up on my 91 75RT. Maybe yours is mounted wrong or the tubes on your tank are different.
    Ron

    91 K75RT ABS

  7. #7
    3 Red Bricks
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    The proper name is Air Accumulator aka "the cup". It's plastic, so it is not a can.

    16 13 2 307 467 AIR ACCUMULATOR $2.26

    The two vent nipples line up with the cup and a hose connects with the drain nipple on the bottom of the cup.

    P1000558.jpg







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    Lee Fulton Forum Moderator
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  8. #8
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    P1000560.JPG

    No, this is not the bike I ride. This is the bike I keep stripped down so that I can take pictures for you guys. One of these days I will restore it.




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    Lee Fulton Forum Moderator
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    Thanks Lee. I have the same cup. My problem is the 2 metal tubings out of the tank do not line up to the cup. I don't know if the tank is from a different year or I just need to rig some fuel tubing down to the cup. I'll try to get some pics later today.

  10. #10
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    Quote Originally Posted by cy7878 View Post
    My problem is the 2 metal tubings out of the tank do not line up to the cup. I don't know if the tank is from a different year or I just need to rig some fuel tubing down to the cup.
    All 2V Kbike tanks should line up. No tubing (except for the cup drain) should be necessary. Take a picture of the cup installation and a picture of the bottom of the tank (one of the side of the tank would tell if it is correct for an S).



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    Lee Fulton Forum Moderator
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    I took a closer look. The straight tube more rearward does drip into the cup and the forward L shaped tube goes lateral to the frame and doesn't seen to connect to anything.
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  12. #12
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    Peel back the heat shielding around the "L" shaped tube. I've never seen a tank with that L. It should be straight and come out much closer to the other tube. Take another picture with the shielding peeled back. Also take another picture of the side of the tank from farther away so I can see the shape of the tank.



    LONG MAY YOUR BRICK FLY!

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    Lee Fulton Forum Moderator
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  13. #13
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    here is what the peeled back shot looks like.
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  14. #14
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    In the last photo, there appears (???) to be a second tube about an inch and a half in front of the straight drain tube. That would be the correct tank drain. I have never seen the L tube on any tanks. Take an air nozzle and blow through each of the tubes to see where they go to.


    Front straight tube should vent the tank behind a baffle in the roof of the tank. Rear tube should go to the rain drain hole on the left side of the filler cap opening. I don 't have a clue what the L does.

    I still want a picture that shows the side (outside painted part from the roundel to the bottom edge).



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
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  15. #15
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    Does it matter if it's a Rs?
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