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Thread: 1978 R80/7 front fork leaking after rebuild

  1. #1

    1978 R80/7 front fork leaking after rebuild

    Recently I rebuilt the front forks. All new seals gaskets and fluid. I torqued everything to spec and all seemed good. I have yet to ride the bike. I keep a cardboard under the front tire while I work on things. I noticed two wet spots under the forks. Sure enough the forks are dripping from the bottom copper crush washer. I thought maybe I didn't put them on correctly or something so I ordered and installed another set. Still dripping. I tried to tighten them further and it helped...for a bit. Still dripping. It's not a huge amount but it shouldn't leak at all. Any suggestions or information is greatly appreciated. Thanks in advance.
    1978 R80/7
    Pacifica, CA USA

  2. #2
    Liaison 20774's Avatar
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    I've never taken those off...usually separated the forks and pulled things out of the slider the other direction. I probably would have tried some Hylomar on the threads and gasket during assembly.
    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. #3
    MonoRT MonoRT's Avatar
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    My 85 is prone to the the same problem. Has been since I bought it new. Perhaps there is some way to re-face the raised surface around the drain bolt hole to get a better seal - but I don't know about that. You sure don't want to strip those little drain bolt threads!

    Like Kurt mentioned, some non-hardening sealer is the way to go. Not wanting to start a sealant treat, I will say that I'm partial to TreBond aka ThreeBond aka YamaBond aka HondaBond. The stuff is grey so it does not stand out too much. I coat both sides of the washer and the last bit of the drain bolt right up under the head. Even with a somewhat used washer like you have now, this seems to make a good seal and stops the dripping without needing to over-tighten that little drain bolt.

  4. #4
    Quote Originally Posted by MonoRT View Post
    My 85 is prone to the the same problem. Has been since I bought it new. Perhaps there is some way to re-face the raised surface around the drain bolt hole to get a better seal - but I don't know about that. You sure don't want to strip those little drain bolt threads!

    Like Kurt mentioned, some non-hardening sealer is the way to go. Not wanting to start a sealant treat, I will say that I'm partial to TreBond aka ThreeBond aka YamaBond aka HondaBond. The stuff is grey so it does not stand out too much. I coat both sides of the washer and the last bit of the drain bolt right up under the head. Even with a somewhat used washer like you have now, this seems to make a good seal and stops the dripping without needing to over-tighten that little drain bolt.
    Thank you for insight. I will try one last time to give it another snug down. Will not strip it I promise. If it fails I'll try the sealant route.
    1978 R80/7
    Pacifica, CA USA

  5. #5
    Airmarshal-IL James.A's Avatar
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    A 1978 front fork is not similar to a 1985 front fork. Find a source for copper crush washers. You'll be glad you did.

    If your front fork is bleeding from the bottom cap, where the bottom bumper grommet resides inside, there are 2 possibilities. 1) Typically, there should be a crush washer installed under the bumper in the "cup", this is at the very bottom, under the bumper. This is the less likely source. 2) You need a heavy duty socket with the face ground down to square to get on that hexagonal "nut" formed into the end of the fork bottom cup. Then, you must torque that end cap as tight as you can get it (with an 18 inch breaker bar) with the fork leg clamped up in a vise. That's right, off the bike, it's the only way. Otherwise you will tweak your forks before you achieve a torque that will seal up that fitting. This will crush the big copper crush washer and seal up the fitting, in a perfect world. The true secret here is to use a small bit of Permatex Holymar on the threads of the bottom cap. Between the big copper crush washer and the Hylomar, the fork will not leak oil at the bottom, unless it is bleeding out of the nut on the bottom of the cup that secures the fork rod to the big cup. (see #1 above) This is less likely in my experience. The weeping around the bottom cup is what I have fought over the years. Use the Hylomar.

    Best of luck.
    Last edited by James.A; 12-08-2015 at 12:06 AM.
    1973 R75/5

  6. #6
    Registered User jad01's Avatar
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    I recently did the same rebuild to mine a few weeks ago… and had the same problem with a small leak from around the new copper crush rings (again, if I recall correctly from the time I did it a number of years back). I simply snugged mine down a little more using the tool kit 36mm spanner while everything was on the bike- worked fine- no leaks so far (about a week and a half…). If the crush washers are new, they should seal fine. Those would be pretty hard to strip using the tool kit spanner...
    Last edited by jad01; 12-08-2015 at 12:56 PM.
    Jim (MOA 83200)
    '78 R80/7 (Anastasia) and '84 R100RS (The Millennium Falcon), '86 K75C (Icy Hot)
    '90 and '93 Mazda Miatas (Jelly Bean and Red Hot), '97 Nissan XE PU (Mighty Mouse)
    '96 Giant Upland (big Kendas, baby!)

  7. #7
    Quote Originally Posted by jad01 View Post
    I recently did the same rebuild to mine a few weeks ago… and had the same problem with a small leak from around the new copper crush rings (again, if I recall correctly from the at time I did it a number of years back). I simply snugged mine down a little more using the tool kit 36mm spanner while everything was on the bike- worked fine- no leaks so far (about a week and a half…). If the crush washers are new, they should seal fine. Those would be pretty hard to strip using the tool kit spanner...
    Thank you for the info. I cranked on it a bit more today. I'll know tomorrow if it helped.
    1978 R80/7
    Pacifica, CA USA

  8. #8
    Drip drip. Damn it. Time to use sealant.


    Last edited by evojet; 12-17-2015 at 05:38 AM.
    1978 R80/7
    Pacifica, CA USA

  9. #9
    Registered User randyd8511's Avatar
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    copper crush gaskets

    Aircraft Spruce is a very good source for those pesky crush gaskets.

    http://www.aircraftspruce.com/catalo...?clickkey=3822
    Randy Williams
    R-100GS, R1100GS

  10. #10
    Quote Originally Posted by randyd8511 View Post
    Aircraft Spruce is a very good source for those pesky crush gaskets.

    http://www.aircraftspruce.com/catalo...?clickkey=3822
    Good to know. I am 15 min away from a BMW dealer. Prices are pretty reasonable.
    1978 R80/7
    Pacifica, CA USA

  11. #11
    Got the forks sealed up with Hylomar. Hard to find stuff. Autozone was my third stop and found one tube there.






    Waited a day to fill and after I filled it's been one days and no leaks.



    Thank for everyone recommendations.
    1978 R80/7
    Pacifica, CA USA

  12. #12
    #4869 DennisDarrow's Avatar
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    Really NICE

  13. #13
    Registered User donbmw's Avatar
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    Quote Originally Posted by randyd8511 View Post
    Aircraft Spruce is a very good source for those pesky crush gaskets.

    http://www.aircraftspruce.com/catalo...?clickkey=3822
    Those are not metric since I work on aircraft have tried many time with no luck.

    Don
    1975 R90/6, 1980 and 1982 R65, 2015 Ural Patrol, 1959 TR3A Triumph Car

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