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Thread: Front forks problems

  1. #1

    Front forks problems

    Hello to all i hope everyone is ok... i have a problem with my R100S 1978 front forks from day one that i got the bike ..... when i seat on the bike fork stay compress....
    i order a rebuild kit and receive it yesterday....
    i remove the forks and rebuild them.... put them back on the bike add the oil close them install the tyre drop it from the center stand and still have the same issue the forks stay compress......
    if i put it on the side stand and pull the bike up they moving but when i push down the forks stay close...


    Can anyone please help me. what i have done wrong

    attached is a photo of the rebuild kit
    44481318_347857779117046_941698320114384896_n.jpg

  2. #2
    Registered User
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    Jun 2009
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    Ft Atkinson Wisc
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    157

    Resourses and links

    It sounds like a sticktion problem.
    This thread from the Resources and Links section of this forum should get you started in the right direction.
    http://w6rec.com/duane/bmw/fork/title.html
    Good luck with your work.

  3. #3
    John D'oh
    Join Date
    Aug 2006
    Location
    Close to Fort Worth Texas
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    611
    There are supposed to be two steel balls, one for each damper rod (07 11 9 986 280) that fit inside the lower damper pipe opening and are held closed by the small springs pictured - which you may have re-used? If you didn't find two steel balls during disassembly, its possible the original ones are rusted stuck in the damper. if you installed the spring and THEN the ball, that would cause a failure. The new metal wiper rings cant be installed as they are but must be fitted to the inside diameter of the fork tube since as they come, they are too big (ring gap to tight) to be installed on the guide support AND be installed in the fork tube. The ring gaps must be filed to fit. So, actually - if you left the balls out or left them stuck in place and put the rings in as they came, I can understand how the fork continues to be non-functional. How did you install the damper assembly into the fork tube? From the top or bottom? With a special tool? Did you encounter any resistance installing the dampers? How much fork fluid per tube did you use?

    Was the lower fork brace/fender mount bracket installed and tightened while the sliders were at the top of their travel? Did you check to be sure it was straight or that the fork tubes were straight and in the lower fork bridge correctly at the correct height and with the two holes at the bottom of each tube to the inside facing each other? Is the axle spacer correct? Do you have the correct spacers in the front wheel bearing stack? Was everything absolutely, spotlessly clean?

    Think back on what you did and consider these statements/questions. There is more to it than just adding new parts. It has to be 'set up' correctly.
    John D'oh

  4. #4
    Registered User lmo1131's Avatar
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    Jan 2010
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    Pismo Beach, CA
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    3,987
    As Franko mentioned. Very good article, but maybe difficult to read through if English is not your native language. > http://w6rec.com/duane/bmw/fork/title.html

    The short version... the fork tube must be parallel with each other, and in the same plane.

    Measuring between the inside of the fork tubes, at top and bottom, will tell if they are parallel.


    Laying a piece of sheet glass (or other flat material) against the "front" surface of the fork tubes will show if they are in the same plane.
    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

  5. #5
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
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    20,551
    Also, when the fork, calipers, fender are installed, care should be taken when tightening. Typically you tighten one section at a time from top to bottom, bouncing the front end in between the sections that are tightened.
    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!

  6. #6
    thank you all for your help... i sort it out.. i unscrew the bottom yoke bolts and axle bolt and seat on the bike put pressure on fork pull them up and down and they worked.. then i screw all the bolts one by one and everytime i was checking the forks if they are working..

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