Fork seals - What's causing this?

Discussion in 'Airheads' started by RaystheBMW, Dec 2, 2012.

  1. RaystheBMW

    RaystheBMW 1986 R65

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    I installed new seals for the first time a few months ago, and the fork keeps seeping oil on both sides. Stanchions are smooth as a baby's behind, and using 300cc Motul 10W. Why is it making this mess?
    [​IMG]
    Are the seals installed upside down? :huh
    [​IMG]
    #1
  2. rambozo

    rambozo Been here awhile

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    Kinda hard to see on my iPod but they look
    upside down to me

    The flat side should face up
    #2
  3. RaystheBMW

    RaystheBMW 1986 R65

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    I'm thinking that too, because the visible edge looks more like a wiper. But if I turn it over, that would put the sphincter spring facing outward, which goes against everything I know so far about seals.
    #3
  4. rambozo

    rambozo Been here awhile

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    Maybe im not seeing the photo clearly enough and you have
    them in the right way

    On my /7 seals the spring was on the inside, although on
    my bandit they're on the outside
    #4
  5. ozmoses

    ozmoses Ride On

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    Is the fork oil getting past the seal at the tube or at the slider?

    Seals are in straight, with no nicks or cuts? Meaning, they went in w/out trouble?

    Part # checks out?

    Fill cap & top nut is tightened?
    #5
  6. georgesgiralt

    georgesgiralt Been here awhile

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    Are you sure 300 cc is the exact amount of oil ? If too much oil is put into the fork, the gasket can't cope with the excessive pressure this will cause....
    #6
  7. RaystheBMW

    RaystheBMW 1986 R65

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    The 300cc oil quantity was confirmed in 2 places, in a manual and online. The seals are an updated version that require a shim sitting on top to keep the dust cap from interfering with the thicker seal. The top fill screw and nut are tight. I didn't consider the possibility of oil running down from somewhere above, or from around the outer perimeter of the seal. I'll take a closer look later. I have a tough time wrapping my brain around the inner functioning of the tubes and sliders, and where the oil circulates to.... I'm sure I'm over-thinking it. So far the only symptoms are a dirty oil line on the tubes at the top of the slider travel, and eventually after a couple rides, the dribble seen in the top photo.
    #7
  8. Solo Lobo

    Solo Lobo airhead or nothing

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    Sometimes the fork braces require adjustment to allow proper leg allignment. If the brace isn't correct and is causing misallignment that may contribute to a leak

    The easy test is that with the wheel off, the axle should slide fully home with light finger pressure. If you have to push hard, something is amiss
    #8
  9. DaveBall

    DaveBall Long timer

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    You might also consider a lighter oil. Those bikes originally came with 5 weight. A lot of people have gone to 7.5 for road use. Some have gone heavier for racing. I tried the Motul 10W in my 82 R100 and did not like the feel of it. Went to 7.5 and it is much smoother. At least to me.

    Heavier oil can cause seals to weep or leak if ridden aggressively.

    I would also recheck the installation of those seals.
    #9
  10. Big Bamboo

    Big Bamboo Aircooled & Sunbaked

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    Another thought, "smooth stanchions" could still be worn out of spec.
    #10
  11. RaystheBMW

    RaystheBMW 1986 R65

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    The axle slides in and out easily.

    Tonight I checked and there is no oil leaking from the top, so definitely from the seal area. I ran a thin feeler gauge around the seal to maybe dislodge any crud that gathered in there.
    #11
  12. ozmoses

    ozmoses Ride On

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    This may not matter but, when you initially installed the sliders w/ new seals did you have a thin film of fork oil on the tubes?

    BTW, this is a K bike type front end?

    You replaced the seals because they were also leaking, I presume & not as a preventative measure?

    I recall my K75 seemed to eat fork seals. Are you certain your forks are straight?
    #12
  13. RaystheBMW

    RaystheBMW 1986 R65

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    The tubes were oiled and I put a light coating of grease on the seals. Yes the later R65 came with a early version of the K bike fork. I'm starting to think my dad had a devil of a time with the oil leaking. He, or somebody, tightened the bejezus out of the top fill screws. And the greasy gunk all over everything when I got the bike was probably fork oil that kept getting replaced. It has only 22K miles, so I'm thinking wear on the metal parts is not a big issue.
    #13
  14. tofgasp

    tofgasp Adventurer

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    Your seals are not upside down. As stated above, you might have an alignement problem of your stanchions wich is quite common on these forks.
    The sliders are not guided as well as in the early models, but just by one teflon ring and 2 small o-ring. You must absolutely reassemble the fork in a specific order otherwise the fork brace twist the tubes, same as the wheel axle, if you tighten the lage bolt before the ones on the sliders, they lightly bend.
    #14
  15. some_guy

    some_guy Been here awhile

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    I'm having the same problem on my R100RT with Type V forks. I pulled off the gators and they were pretty much filed with fork oil. I just bought seals (bike is new to me I don't know if they've ever been replaced), but I don't know the assembly/alignment proceedure . Know of a good guide?
    #15
  16. RaystheBMW

    RaystheBMW 1986 R65

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    When I disassembled, I just pulled the front wheel, fender, and caliper, drained the sliders and and removed the vertical allen screws on the very bottom inside where the axle goes. Then the whole slider assembly pulls down and away. I didn't disturb the upper tubes at all, except for removing the fill plug.
    #16
  17. some_guy

    some_guy Been here awhile

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    This is what I was planning on doing, but if there's a alignment checking/adjusting procedure I'd go through that as well.
    #17
  18. chollo9

    chollo9 Screwed the Pooch

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    Yeah, at this point, I'd "disturb" everything. Disassemble, clean & inspect, check tubes against a very good straight edge, etc. If the tubes are straight and everything else looks good, it would be worth checking the tubes with a mic, but wear usually is apparent visually.

    I'd also only lube with grease upon reassembly, that way you'll know where the oil comes from if you get any.
    #18
  19. hoss18

    hoss18 Been here awhile

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    I know this is an outside chance but are the seals OEM or copies. Im only mention it because I had the expereince of buying a set from offline that I couldnt get to seal - always leaked from day one. Eventually pulled them out thinking something wrong with tubes etc but by chance measured the seals and they were about 1mm to big. Put OEM ones in and they havent leaked. Never heard of it before or since.
    #19
  20. H96669

    H96669 A proud pragmatist.

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    ^^^ You may be right, my friend sure had "online copies" leak. But those look like OEM with some of the metal exposed. Not that good BMW leaving some metal exposed.:evil Road salt got under the caps on my bike and rotted the metal. They sure leaked then....! I grease them now and inspect every year. Different bike....same seal design.:eek1
    #20