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Thread: Removing air filter-1992 K-75RT

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  1. #1
    Dale Rudolph
    Join Date
    May 2009
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    Medford, Oregon
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    Removing air filter-1992 K-75RT

    The first and last time I changed the air filter on this bike, I also changed the fuel filter and anti freeze. Changing the anti freeze requires taking the tank off, which is why I didn't have any trouble getting the air filter out.

    I tried to get the air filter out of the air filter case today, but the upper part of the case will not lift high enough to pull the filter out. The owners manual says to release the three spring clips and lift the upper case to pull the filter out, the Haynes manual says to remove the tank.

    Has anyone come up with a way to get the filter out without removing the tank?

    My second question concerns whether leaving the "Choke" lever fully open for a month would have an effect on the bike now not starting? About 5 weeks ago, I changed the oil and ran the engine for a few minuets afterward. Between having surgery and bad weather, I just today tried to start it, this is the first time it has ever failed to very quickly start for me. Would having the "Choke" lever open for the last
    five weeks cause either flooding or allowing all the fuel in the injection system to evaporate? If this wouldn't having any effect on the bike not starting, I will check the fuel pump and plugs.

    Thanks for any suggestions.

  2. #2
    Benchwrenching PGlaves's Avatar
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    Oct 2003
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    The "choke" is nothing more than a cable that pulls the throttle slightly open. It has nothing to do with the delivery of fuel whatsoever.
    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://www.bigbend.net/users/glaves

  3. #3
    Registered User
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    Apr 2005
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    Kansas
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    Air Filter

    The answer to your first question is "probably not". That also probably has to do with latching and unlatching those clips. I have two K100RTs and I check the filters every time I have the tanks off. The word there is Check. Check for butterfly guts and squirrel corn. You think I am kidding. Tap the filter on the bench a few times and replace the old filter. The 120k bike has had two filters one at 50k and one at 100k. Not because I thought they were plugged or not doing their job but because I thought they deserved them. K filters are way over capacity.

    The answer to you second question is a definate no. The Choke simply raises the idle ,opens the throttle, by two steps then falls back to one step. K75s do flood on occasion, if there is a slow start. Check the plugs for wet and if they are put in new dry plugs.
    Harold In Kansas
    1985 K100RT Bullit
    1985 K100XX/EML Bemel

  4. #4
    Dale Rudolph
    Join Date
    May 2009
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    Medford, Oregon
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    Thanks for the replies.
    I took the plugs out, they were slightly wet, they only have about 2,000 miles on them. I dried and cleaned them, the bike started and ran very rough for about 5 seconds and would not re-start.
    I will drain most of the fuel out of the tank and see if just raising the rear of the tank will give me enough room to get the air filter out.

    While most of the fuel is out, I'll see if the pump works with the switch and if it does, see if fuel is reaching the fuel injection rail.

    Any suggestions on where to buy a fuel pump if that should be the problem?

  5. #5
    Benchwrenching PGlaves's Avatar
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    The plugs were "wet". Unless it was water, fuel is getting to the rail. If it was water it was the fuel pump that pumped it there from the tank.
    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://www.bigbend.net/users/glaves

  6. #6
    BMW uber alles! Zagando's Avatar
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    Rockport, TX
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    Airbox Wrestling 101

    The reason you will need to remove the tank is so you can stick a long flat-bladed screwdriver between the maze of wiring (underneath it) above the air filter box to loosen the cable clamp screw that clamps onto the plenum deep inside the "interior". While it may be technically possible to remove the air filter without doing so I rather doubt it would work without causing major aggravation.

    If you loosen the air filter top by undoing the three spring clips AND the plenum intake pipe then you can wiggle the top up and out enough to pull the air filter.

    It also helps to pull up on the wires above it to give it every possible fraction of a millimeter of much needed space, too!

    When you put the air filter back in remember to tighten the plenum pipe clamp before you put the tank all the way back on. Make sure that the filter orientation is correct (only one way it goes in) and it also helps to put a light coating of Armor All or Back to Black along the edges for lubrication.

    After doing this a few times you will get the hang of it and I assure you that removing the tank is dead simple by comparison. Getting those spring clips back in place is also quite tricky but a pair of long forceps (Harbor Freight $3) really makes it a lot easier.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  7. #7
    RK Ryder
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    Sep 2005
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    London, Ontario
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    I lift the back of the gas tank and insert a short 2x4, to hold the tank up about 4" and then slide out the old filter and then in with the new one.
    Paul
    Retired and riding my RTs, the '87 K100 & the '98 R1100 !
    Treasurer of the Forest City Motorrad Club #159
    Knights of the Roundel #333

  8. #8
    Dale Rudolph
    Join Date
    May 2009
    Location
    Medford, Oregon
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    579
    I have to wonder if the "Wet", if it is water, is a result of ethanol setting in the tank for close to 2 months. I use both, a fuel preserative and an ethanol treatment.
    I drained most of the fuel out and took the fuel cap off the tank, with the switch on and touching the starter, I could hear the pump and also see fuel moving around in the tubing.

    I guess my next step will be to change the fuel filter, the local BMW shop is closed for the next week. I know there is a list of other filters that will work, any one of them more advisable than others?

    I remember the last time I took the tank off, the thing I had the most trouble with was the two brass clips that hold down the rear of the tank to the frame. They come out much easier than they go back in.

    Thanks for the opinions.

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