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Thread: '95 K1100LT ABS brake bleed

  1. #1

    '95 K1100LT ABS brake bleed

    My 1995 K1100LT with ABS started locking up the front brakes and the master cylinder began leaking so I had my mechanic install a Magura master cylinder rebuild kit from Beemer Boneyard and replaced both front and rear lines with a stainless steel lines kit from Spiegler Performance Products but can't seem to get the system to bleed. We tried "back bleeding" through the bleeder valves and still no pressure. What's the trick to resolving this issue?

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    Besides the back bleeding, what methods have you tried?
    Pressure flush thru the master cylinders?
    Pump/bleed/release?
    Miti-vac?

  3. #3
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    Bleeding of the front brakes must be done with the handle bars turned all the way to the left. Because of the way the master cylinder is mounted to the bars, the outlet end of the cylinder is higher than the rest of the bore, making air go towards that end. But the outlet at that end is on the BOTTOM of the bore thereby trapping air at the top of the bore at that end.

    By turning the bars all the way to the left, the outlet end become lower than the rest of the bore, allowing the air to go to the opposite end and back up to the reservoir.

    It's also best if you are having problems bleeding the fronts to push the pads and pistons all the way back into the calipers. This can be done with small wedge shims like the ones used for shimming door jams. I prefer the plastic ones as they taper down to much thinner. You might have to unbolt the calipers from the forks if you don't have thin enough shims. With the rotor not in between the pads, you can use much thicker shims to hold the pads all of he way back.


    Bleed the ABS modulator first, then the left front caliper. The front modulator is the one on the left.

    Edit: Post 7/93 K1100s use the second generation modulator. Both are incorporated into one unit. I don't remember where on the bike they hide it or which side is for the front and which side is for the rear. I'm currently at NorCals 49er Rally, so I won't be able to look it up until Tuesday or Wednesday.





    Last edited by 98lee; 05-29-2019 at 10:45 PM. Reason: Correction
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  4. #4
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    [QUOTE=98lee;1167738]Bleeding of the front brakes must be done with the handle bars turned all the way to the left. Because of the way the master cylinder is mounted to the bars, the outlet end of the cylinder is higher than the rest of the bore, making air go towards that end. But the out let at that end is on the BOTTOM of the bore thereby trapping air at the top of the bore at that end.

    By turning the bars all the way to the left, the out let end become lower than the rest of the bore, allowing the air to go to the opposite end and back up to the reservoir.

    It's also best if you are having problems bleeding the fronts to push the pads and pistons all the way back into the calipers. This can be done with small wedge shims like the ones used for shimming door jams. I prefer the plastic ones as the taper down to much thinner. You might have to unbolt the calipers from the forks if you don't have thin enough shims. With the rotor not in between the pads, you can use much thicker shims to hold the pads all of he way back.


    Bleed the ABS modulator first, then the left front caliper. The front modulator is the one on the left. Edit: K1100s use the second generation modulators. Both are incorporated into one unit. I don't remembet where on the bike they hide it or which side is for the front and which side is for the rear. I'm currently at NorCals 49er Rally, so I won't be able to look it up until Tuesday or Wednesday.

    QUOTE]


    I think that turning the bars to the left AFTER bleeding, and parking the bike on its sidestand, allows and air left in the lines (non ABS) to work its own way up to the master cylinder, and thus out of the system. And turning the bars to the left does put the feed hole from the reservoir to its lowest point. But if turning the bars to the right leaves your feed hole uncovered and exposed to the air in the cylinder it seems to me that your reservoir is underfilled. Wouldn't you be introducing air into the system every time you do a low speed right turn and apply the breaks?

    The use of the plastic shims is a great tip.
    Last edited by 98lee; 05-29-2019 at 05:57 PM. Reason: Oops, I was trying to edit the spelling in my previous post and hit the wrong post. Sorry

  5. #5
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    Quote Originally Posted by JeffDiCarlo View Post


    I think that turning the bars to the left AFTER bleeding, and parking the bike on its sidestand, allows and air left in the lines (non ABS) to work its own way up to the master cylinder, and thus out of the system. And turning the bars to the left does put the feed hole from the reservoir to its lowest point. But if turning the bars to the right leaves your feed hole uncovered and exposed to the air in the cylinder it seems to me that your reservoir is underfilled. Wouldn't you be introducing air into the system every time you do a low speed right turn and apply the breaks?

    The use of the plastic shims is a great tip.
    It is not about the feed hole being exposed to air (if that ever happens, your fluid level was WAY too low). It is about when you already have air in the system (such as after a brake hose change) and you are trying to get the existing air out, air can get trapped in the left hand upper section of the master cylinder bore. All the bleeding in the world won't help if a pocket of air is trapped there because the fluid will travel underneath this pocket of air. If you make this pocket so it is not at the high point in the system (by turning the bars to the left) the air travels right out during the bleeding process.

    Look closely at the outside casting of your mastercylinder with your bike on the centerstand and the bars pointed straight ahead. You will notice that the inner end (left end) of the master cylinder bore is higher than the rest of the bore. With the outlet of the bore (where the hose connects) being on the bottom, fluid will bypass the trapped air above it in that tip of the bore.



    Last edited by 98lee; 06-01-2019 at 01:39 PM. Reason: Sp.
    LONG MAY YOUR BRICK FLY!

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  6. #6
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    Quote Originally Posted by 98lee View Post
    It is not about the feed hole being exposed to air (if that ever happens, you fluid level was WAY too low). It is about when you already have air in the system (such as after a brake hose change) and you are trying to get the existing air out, air can get trapped in the left hand upper section of the master cylinder bore. All the bleeding in the world won't help if a pocket of air is trapped there because the fluid will travel underneath this pocket of air. If you make this pocket so it is not at the high point in the system (by turning the bars to the left) the air travels right out during the bleeding process.

    Look closely at the outside casting of your mastercylinder with your bike on the centerstand and the bars pointed straight ahead. You will notice that the inner end (left end) of the master cylinder bore is higher than the rest of the bore. With the outlet of the bore (where the hose connects) being on the bottom, fluid will bypass the trapped air above it in that tip of the bore.



    Lee, good idea. Can't say I've had that problem so it never occurred to me.

  7. #7
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    Jeff,

    I'm not meaning to say that everyone WILL have this problem, just, if they are having problems, this could be the cause.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

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

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