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Thread: Sticking front wheel

  1. #31
    John D'oh
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    You need a $5.00 air blowgun with a rubber tip. One of the two ports must be closed off by reinstalling the bleed valve and tightening it to ensure high pressure air introduced in the other port acts on the piston. 80 psi is more than enough pressure. Did you understand what the wood backstop is doing? Properly positioned it prevents the piston from damaging the opposite caliper pad support structure as it is pneumatically driven from its bore. If your master cylinder is bad it will show up when everything is back together and you start the bleeding process. Otherwise you could remove the plunger to check the bore and seals.
    John D'oh

  2. #32
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    Pistons have been removed

    Following advice from Na Cl K9 I purchased a new nossel and removed the pistons. I'm not certain that I really wanted to see the inside of the calibers. Both pistons appear to be in decent condition. The calipers not so much. I've taken a couple of pics but I'm afraid I do not know how to include pics with my post. I'm wondering if the calipers can be cleaned out with a gentle honing. A quick survey of a couple of BMW parts vendors indicate a price of $400+ for new calipers. This is well outside of my current budget. I welcome any advice. This motorcycle has a gorgeous paint job and I have a set of new stainless exhaust pipes in the basement. I've just begun to realize why the selling price seemed so reasonable.

    rickt

  3. #33
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    This page may help you with picture posting-

    https://forums.bmwmoa.org/showthread...picture/page53

    Good luck.

    Gary
    "You can do good or you can do well. Sooner or later they make you choose." MI5
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  4. #34
    Liaison 20774's Avatar
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    Quote Originally Posted by r65lsk75c View Post
    I've taken a couple of pics but I'm afraid I do not know how to include pics with my post.
    To upload a picture, check out post #15 here:

    https://forums.bmwmoa.org/showthread...=1#post1159528
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #35
    John D'oh
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    Check the pistons with a magnet to see if they are stainless steel. Pistons must be free of rust pitting. I hope that what you see in the caliper bore is simply debris and not oxidation. I’ve never considered boring a caliper to restore the surface simply because there are no over-sized pistons available. Try ‘brake parts cleaner’ and see what happens.
    John D'oh

  6. #36
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    Apparently not stainless

    Quote Originally Posted by Na Cl K9 View Post
    Check the pistons with a magnet to see if they are stainless steel. Pistons must be free of rust pitting. I hope that what you see in the caliper bore is simply debris and not oxidation. I’ve never considered boring a caliper to restore the surface simply because there are no over-sized pistons available. Try ‘brake parts cleaner’ and see what happens.
    Hi John. The pistons are not stainless. Both have just a couple of tiny spots of rust. In my humble opinion, they are useable. Of more concern is the calipers. More searching gave me only used items. I'm thinking that I need to salvage the current calipers. Is it acceptable to work on the inside with very fine 2000 wet/dry grade emery paper or steel wool? I also noted that the seals are rather expensive. On one of the calipers the seal is still partially retained. The calibers contained a fair amount of insoluble gung. I now need to look more closely at the MC given the current state of the downstream brake system. Please let me know your thoughts on cleaning the inside of the calipers.

    Thanks
    Rick T

  7. #37
    Attempting to clean the caliper bores is worth the try. Reusing a seal because a new one is "expensive" is not even worth thinking about. Your health, safety, and life depend on those brakes.
    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://web.bigbend.net/~glaves/

  8. #38
    John D'oh
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    Quote Originally Posted by PGlaves View Post
    Attempting to clean the caliper bores is worth the try. Reusing a seal because a new one is "expensive" is not even worth thinking about. Your health, safety, and life depend on those brakes.
    What Paul said.

    You could use progressively ‘hotter’ solvents till you find something that cuts the gunk. As a last resort 0000 steel wool would be the limit of what I would ever use to restore a caliper bore surface finish. To some extent the caliper doesn’t need to be perfect but the piston does. Run your fingernail across those rust pits and you’ll feel the rough spot and even leave a little nail behind. That's the issue - the rust pits eat the seals. Here’s the deal - replace the rusted piston(s), install new seals and dust covers, new pads, new hoses, DOT 3 or 4 fluid. Replace the O’ring under the master cylinder reservoir and then bleed the system once a year. Done right it should last 30 years or more and that makes your investment seem insignificant compared to the return. Done cheaply and it’s like you place a rather small value on your life. By the way, this is only the first chapter in the book of ATE. Are you familiar with Snowbum’s web site? Lots of info there. “RUZNEB” and “BEEMERUSS” nailed it at the beginning of this thread by the way. See where this is going?
    Last edited by Na Cl K9; 07-08-2019 at 10:30 PM.
    John D'oh

  9. #39
    There are plenty of tools designed to hone calipers out there. But. You're already on a bike with skinny tires and mediocre brakes compared to modern traffic. If it's just crud, clean it and rebuild it with new seals. If it's rust, then replace. And this is why changing brake fluid every year on bikes and every two on cars is good insurance.
    '61 Clubman's Gold Star, '13 690 Duke, '13 Daytona 675R, '17 1290 GT, '18 Street Triple RS (gone but not forgotten: '76 R75/6, '84 R100, '76 R90S)

  10. #40
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    Confusion is beginning to overwhelm me

    After removing the residue from the piston seal/dust cover (not sure which it is) I encountered what appears to be a thin type of rubber? coating on the inside of the caliper wall. This was a bit of a surprise as I have not seen this on any R90S parts fiche. Am I imagining things or is this a normal part of the caliper? So, I really don't know where to go from here. I have ordered 2 "Protection Caps" and 2 other caliper parts. I am at a loss as far as attempting to clean the caliper bores. I have not been able to find new pistons on any of the vendors part fiche. Can anyone rescue me?

    rickt

  11. #41
    John D'oh
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    Really, we need to see photo's now. I cant imagine what it is you are looking at.The actual piston seal is a round rubber ring with a square cross section. The dust cover is a wide rubber and steel membrane that installs in the caliper and surrounds the piston brake pad support. Don't clean the dust cover. Throw it away with the square seal and the piston.
    John D'oh

  12. #42
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    I will try to send pictures

    I’ve taken a couple of pictures but their not great. Still trying to transfer from my iPad.

  13. #43
    John D'oh
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    Note that large image files will not upload. If you’re having problems try reducing the file size.
    John D'oh

  14. #44
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    Appreciate all of the assistance

    John, you have gone out of your way to provide numerous recommendations on my brake issues. My problem among numerous others comes from a stroke 6 or 7 years ago. I struggle with numerous basic things like finding a way to attach pictures to a post. So, I have a few pictures taken with my iPad but have not been able to attach them to a post. I'm hesitant to ask but can you provide a more effective way for me to accomplish this amazingly difficult feat? I am more than happy to send to your private account if I knew how to do this.

    rickt

  15. #45
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    Pictures of calipers and pistons

    Hoping that I have attached pictures of the R90S calipers and pistons. Looking for suggestions on how to handle the calipers and if the pistons should be replaced. I have not found a source of replacement pistons.

    rickt
    Attached Images Attached Images

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