F800ST Steering damper rebuild - BMW F800 Riders Forum & Registry



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  1. F800ST Steering damper rebuild

    14 Comments by Strelok89 Published on 04-25-14 08:17 AM
    today i rebuilded 3 F800ST(2007) steering dumpers
    i used motorex 10W fork oil
    every steering damper needs 16CC of oil.

    my english is not good enough to post full job review, so i will put pictures and will try my best to explain if some one don't understand anything

    https://www.facebook.com/media/set/?...1&l=7f62403060
    Si fractum non sit, noli id reficere

    education is important, but RACING is importanter

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  4. #2
    Mokkybear's Avatar
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    Thanks Alex - good job. Would be useful if you could annotate the photos if possible so we could understand better what's happening. Some questions:
    How did you determine what oil was appropriate, and the volume?
    Did you replace seals and anything else?
    I notice some emery paper - did you use that to 'dress' surfaces?
    Have you been able to compare damping characteristics of a rebuilt damper with an original (e.g. join the two rods with a nut and push/pull to see if they move at similar rates)?

    Cheers, Alex.
    R1200R-LC ​Exclusive in Thunder Grey with Touring Pack. Formerly Graphitane F800ST 04/2007. I rarely visit the forum these days ... 

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    Strelok89's Avatar
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    The oring on the rod valve is 19x2 mm
    I reused the old oil seals.
    Used the emery paper 1000 grade with oil to remove the oxidation and to make the rod smooth, so the seals wouldn't be damaged.
    I used 10w because I had at home some oil left from the forks rebuild on my f800st, and I rad on k1200lt forum that some German guy used 10w oil for the steering dumper.

    I've compared the 3 dumpers but they all from 2007 f800st so they not a good references.
    Just rode on speeds of 200km/h with side winds and was no wobbling and tank slapping.
    Before rebuild (yesterday) the handle bar was wabling at 160-180km/h.
    So for now the 10w fork oil works great as damper fluid, the handle bars not hard to rotate. I will try in about a month or so 15w fork oil from motorex to compare


    I will try to annotate the pictures but sorry for the English.
    Si fractum non sit, noli id reficere

    education is important, but RACING is importanter 

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    Very similar to the damper on the old K100s. Mine was knackered and my wife would not let me steal the one on her F800 so I bought an adjustable from ebay for around £30. It works very well.
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    Past bikes: R75/7 1977, K100LT 1990, R1150RT 2003, K1200GT 2004, R1100S 2001, R1100S 2004, 

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    Mokkybear's Avatar
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    It seems the 10W does the trick, Alex. Thanks again for the post and the pictures.
    R1200R-LC ​Exclusive in Thunder Grey with Touring Pack. Formerly Graphitane F800ST 04/2007. I rarely visit the forum these days ... 

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    this is the first step, using 2 13MM wrenches.
    and you removing the plastic cap from the other side, and using emery paper and oil cleaning any oxidation and rough surfaced so the oil seals wouldn't get damaged during disassemble


    then remove the snap ring
    and using big needle or very small screw driver remove the washer.


    put some thing big to catch the oil and using rubber hammer remove the rod with the center valve and cooper spacer, all the oil going to split down on this step so you really want something to catch it under.



    now remove the snap ring and the washer of the other side, put only the rode back and using rubber hammer remove the second oil seal and cooper spacer


    clean every thing.
    i used paper towel and some wd40.
    Si fractum non sit, noli id reficere

    education is important, but RACING is importanter 

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    now assembly,
    you what to replace the o-ring on the main rod valve, it's 19X2 MM buy from any place you like just make sure the material can handle oil, i used NBR just as oem


    this side is the first to assemble

    now take the cooper spacer and put it in , make sure the thick side of it facing out side of the steering dumper.


    next using 13MM socket and rubber hammer put the oil seal

    next put the washer and the snap ring.


    make sure the rod is slightly oiled, clean and the valve o-ring is oiled, put it in.


    put 10CC of 10W fork oil, the move the piston carfully up and down to make sure the air got out.
    next put another 5CC of oil and the put the cooper spacer in, again the thick side facing outside.
    now put approximately 1cc of oil and very careful move the rod to make sure the air is out and the oil is at the top of the cooper spacer.
    if the oil is higher than the cooper spacer then suck or spill a little bit, if the oil too height you can't fully assemble the oil seal.
    the oil should be covering the whole cooper space but not higher .

    next using 13MM socket assemble the oil seal and the washer and the snap ring.
    next assemble the rod end , i used EP2 grease to slightly grease the joints and that's all.
    Si fractum non sit, noli id reficere

    education is important, but RACING is importanter 

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    on the same couch and coffee table i rebuilded cbr250 engine
    Si fractum non sit, noli id reficere

    education is important, but RACING is importanter 

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    Great post, Alex - perhaps a moderator can copy/move it to the Hall of Wisdom for ready reference in the future.
    R1200R-LC ​Exclusive in Thunder Grey with Touring Pack. Formerly Graphitane F800ST 04/2007. I rarely visit the forum these days ... 

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    How long did the steering damper last before it was time for a rebuild?
     

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    Alex

    I have moved this thread to the Hall of Wisdom as suggested

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    Quote Originally Posted by Brickhead View Post
    How long did the steering damper last before it was time for a rebuild?
    very hard to say my bike is 10/2006 manufacture date , 02/2007 sell date i am the 4th hand i have 63000km on clock i guess i am the first to touch it.
    my father's st is 10/2006 manufacture date 2007 sell date and he is the 5th hand and 64000km on clock and i guess he is the first to touch it.
    the third damper bought by my friend with approx 30000km on clock and he replaced it on approx 130000 km on clock.

    my father's one was the worst case, it was full of water and debris inside and almost not worked.
    mine was better, but still not in good shape
    my friends one had badly worn out main valve o-ring

    now all of them working really well, my guess every 2 year is a good practice to change the oil, at the same time as changing fork oil
    Si fractum non sit, noli id reficere

    education is important, but RACING is importanter 

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    I know this is an old post, but I was just in the middle of a front end overhaul on my ST which has 60,000miles and decided that my damper needed some attention since I had it off the bike. I followed the instructions above and was able to rebuild it. I didn't replace any parts, but after a thorough cleaning and fresh oil, it feels much smoother now. I used 5w fork oil and must comment that it took a lot more than described above. I found that the little cup that comes with children's liquid medicine was ideal for measuring and pouring the small amounts of oil needed. I had to work it back and forth MANY times to get the air out and completely fill it with oil. I was really starting to get worried after 5 min of pumping and still feeling air bouncing the piston back. Also, I found that a rubber mallet wouldn't cut it. I needed a real hammer with a block of wood to protect the shaft to knock the seals out while the body was in a bench vise. They were stuck in there pretty good.

    I also had a question in case anyone knows... The copper spacers on each side had what appeared to be a bunch of hardened gunk in their groove, but after watching a bunch of other videos of other dampers being rebuilt, it looks as if these spacers might have had some sort of mesh or foam filter in that groove. Hopefully not, because now mine are just clean and empty.

    Anyway, I'm glad I saw this post because it gave me the confidence to do it. My "renewed" damper has a bit of a squeak now, but it is much smoother.
    Last edited by ccramerusc; 1 Week Ago at 05:45 PM.
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  27. #15
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    Yes, there is a foam seal between the spacer washers.
    When I have rebuilt my damper last year, I had to remove this foam because it was junk as well. I don't understand the purpose of this foam seal, execpt maybe improve the damping effect. For my rebuild, I have decided to go for a 15w oil, as in my fork, and I think it has compensated the lack of foam because it works fine since...

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