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Thread: Sticking front wheel

  1. #61
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    Next steps

    As I wait for the new parts to arrive, I need to remove the sealing ring that resides inside the caliper and clean the caliper. What is the best method for removing this seal without damaging the caliper? Given the state of the front brakes, I'm wondering if I should more carefully examine the master cylinder? Suggestions on how to proceed will be appreciated.

    rickt

  2. #62
    Liaison 20774's Avatar
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    I'd study what Brook has posted here:

    https://brook.reams.me/bmw-motorcycl...ster-cylinder/

    Notice that he uses a pick and carefully grabs the square o-ring and pulls it out of the groove.
    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!

  3. #63
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    Master cylinder rebuild

    Given that I now have the calipers under repair, Iím thinking that the master cylinder should be carefully examined (rebuild?). The parts fiche shows two repair kits. One for bikes to 09/1975 16mm, the second for bikes from 09/1975 17mm. My R90S is 1975. Is there any way for me to determine which kit is correct for my bike without taking the MC off and apart?

    rickt

  4. #64
    Liaison 20774's Avatar
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    Did you look at the link I posted? Brook documents how to tell what size master cylinder you have...it's stamped on the body of the part.
    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. #65
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    My bad

    I did quickly read through the article. Obviously I did not pay close enough attention to the details.

    rickt

  6. #66
    Motorsickle Rider brisco's Avatar
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    I see several single 40mm calipers on eBay. Various prices. https://www.ebay.com/itm/76-BMW-R100...QAAOSwPEdc1NR7 is one, there are more. I searched for bmw 40mm caliper r90s

    Good luck!
    Brian
    Kansas. Eleven curves in three hundred eighteen miles...
    '09 R1200RT, '70 R75/5, '73 R75/5, '11 Ural Patrol
    N0PGH
    Iron Butt Assoc. #47865

  7. #67
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    MC Repair Kit

    I managed to remove the MC from the bike frame. The exterior will need to be cleaned and painted. Examination of the piston with a caliper indicated a diameter of 17.43 mm. There are two MC repair kits listed on microfiche. Part # 34 31 1234925 for D=16 mm and part # 34 31 1234927 for D=17 mm. There is no size marking on the outside of the MC. Can I assume that the 17 mm repair kit is correct for my R90S?

    rickt

  8. #68
    Liaison 20774's Avatar
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    You should have seen a number in the casting like Brook shows here:

    https://www.flickr.com/photos/brook-...7675789624605/
    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!

  9. #69
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    This is how I am reminded

    Being reminded of my mental deficiencies happens much too frequently. Indeed the 17 was right on the casting where it is supposed to be. Onward I go.

    rickt

  10. #70
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    Update and A New Issue

    As suggested, I did find a 40mm caliper on Ebay. I painted all three calipers and the MC with black epoxy and ordered a second 40mm caliper rebuild kit. I decided to rebuild the MC and ordered the appropriate kit. Now, another case of memory failure. I misplaced/lost the MC fluid container, cap and allen screw that holds it to the MC. I typically put all parts in a zip-lock bag for safe keeping but it was no where to be found. I called Bob's and ordered a new fluid container. After some further investigation, I determined that the allen screw that is used to attach the fluid container to the MC is not available. The flanged screw/bolt appears by my guessing to be thread 1.0 and 10-11 mm in width. Any suggestions where I might find this part or anyone who may have a spare would be greatly appreciated.

    rickt

  11. #71
    [QUOTE=r65lsk75c;1176894 Any suggestions where I might find this part or anyone who may have a spare would be greatly appreciated.

    rickt[/QUOTE]


    Youíre into this resuscitation a bit, but if/when you decide you want professional mechanical help (or a source for parts), youíre lucky to have Charlie Johnson, an excellent airhead mechanic, not far away in Wayzata, MN. (952) 449-0357.

  12. #72
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    Getting past the frustration

    As suggested I made the 50 min. drive to Charlie Johnson's shop in Victoria. He did have the proper allen-head screw for mounting the fluid reservoir to the master cylinder. The MC is now securely strapped to the top of the bike frame. Now I will venture onto the assembly of the calipers while hoping for no undesirable setbacks.

    rickt

  13. #73
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    Inserting Pistons into Calipers

    I'm guessing that I am displaying a high degree of incompetence. Everything is clean and following the procedure outlined in Brook Reams notebook I cannot get the piston to enter the caliper. No amount of juggling, pushing or attempting to turn the piston was successful. I lubed the side of the piston and the seal with
    brake fluid as suggested. I am reasonably certain that the piston is aligned correctly. Am I missing something? Are there other means of making the piston cooperate? Is the use of a C-clamp to push the piston in totally inappropriate? Any suggestions will be appreciated.

    rickt

  14. #74
    Quote Originally Posted by r65lsk75c View Post
    I'm guessing that I am displaying a high degree of incompetence. Everything is clean and following the procedure outlined in Brook Reams notebook I cannot get the piston to enter the caliper. No amount of juggling, pushing or attempting to turn the piston was successful. I lubed the side of the piston and the seal with
    brake fluid as suggested. I am reasonably certain that the piston is aligned correctly. Am I missing something? Are there other means of making the piston cooperate? Is the use of a C-clamp to push the piston in totally inappropriate? Any suggestions will be appreciated.

    rickt
    Not incompetence; it's the experience I had. Get some red rubber grease. https://www.ebay.com/itm/20g-Genuine...oAAOSwZrhaeH-L It is not typically available locally (at least around me). I learned about it reading Brit bike magazines. Every year or so thay'd have an article on rebuilding calipers. And every one used red grease.

    I have used a c-clamp and it didn't seem to cause much damage but the grease is the way to go.
    '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)

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