airhead valve cover oil leak -- easy fix??

Discussion in 'Airheads' started by AirScoop, Mar 27, 2010.

  1. AirScoop

    AirScoop Adventurer

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    Just finished some top end work on my '83 ST, and I am puzzled as to why I can't seem to stop the oil leaking from my left side valve cover. I had removed the old gasket, which was pretty well cemented onto the head, cleaned the residue off the head, and installed a clean, dry new gasket. (I elected to leave the old gasket on the right side after seeing how difficult it was to get the old one off the left side. Naturally that side isn't leaking.) Valve cover center nut torqued to spec. Ran the bike in the garage a couple of times with no leaks while running; however, a pretty fast oil drip began from the bottom of the left valve cover shortly after I killed the engine.

    Decided to try again with another new gasket (the one I had intended to use on the right side), and took the bike for a good long ride to get the head up to temperature. Again, no leak while running, but almost instant oil drip when stopped.

    No doubt there is something I am overlooking here. Any ideas, airhead gurus?
    #1
  2. Steptoe

    Steptoe steptoe

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    Try using two gaskets. And don't overtighten the two end nuts to try and stop the leak. It distorts the cover so causes more leaking :D
    #2
  3. Yarddog

    Yarddog Been here awhile

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    Sounds like maybe a warped valve cover...I usually use #2 Permatex on gaskets, BUT...they recommend that these be installed dry, which makes good sense since they are frequently removed for valve adjustment...so yeah, try the double gasket trick first...while you got the cover off check and make sure it's true, but that might be difficult...only takes a little bit to cause this problem, more than likely...
    #3
  4. BrianK

    BrianK F'in' half ass lookie boy

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    I has this happen to me, and using two gaskets cured the problem. Then I replaced the two gaskets with a single silicone gasket, which worked well also.
    #4
  5. AirScoop

    AirScoop Adventurer

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    How convenient! I happen to have two gaskets! I'll try it and report back.
    #5
  6. AirScoop

    AirScoop Adventurer

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    Bingo. Two gaskets did the trick.

    I wonder if I installed the valve cover upside-down relative to the way it was before I did the top end work? Right now, the "L" is visible on top. Is there a "correct" orientation?
    #6
  7. P B G

    P B G Long timer

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    There's a L and an R, and the threaded studs for the nuts are offset so if your L is on the R it will be turned and rotated.

    It is possible to inspect for flatness. The studs are problematic, easiest if you have a sheet of glass to drill some holes in it to match then you can check for gaps/rocking. To flatten them the studs would have to be removed.
    #7
  8. AirScoop

    AirScoop Adventurer

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    The valve cover marked "L" is indeed on the left side, with the L oriented to the top of the cylinder. It seems to fit okay if rotated 180 degrees so the L faces down. Is there a proper orientation ("L" up or down)?
    #8
  9. Wirespokes

    Wirespokes Beemerholics Anonymous

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    The scraped side goes down. :wink:

    But seriously - it doesn't matter if the L/R is up or down.

    Supposedly, oil on the mating surface will glue the gasket to that side by carbonizing when it gets hot. So you'd want to have an oil film on one side and not the other. I'd prefer the gasket glued to the cover and not the head.
    #9
  10. bmwrench

    bmwrench Long timer

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    You are experiencing the effect of a warped cylinder head. 81 on heads are prone to this. If you remove he gasket(s) and put the cover on, you'll be able to see a gap between cover and head just above and below the valve spring cavity. The ideal cure is to plane this surface while the heads are off. The next best is to fill the gap with sealant or use a silicone gasket.
    #10
  11. AirScoop

    AirScoop Adventurer

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    Ah, too bad. And I just had the head at the machine shop to have the stripped hole for the valve cover stud repaired (PO had installed a time-sert that had failed). No doubt the machinist could have fixed me right up!

    For now, it looks like the double gasket trick has stopped the leak, so I think I'll run with it like this and keep my eye on it. I am not too eager to take the head off yet again, as the bike has sat all winter and I'm ready to start riding! :D
    #11
  12. rtw02

    rtw02 Been here awhile

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    Silicone gaskets are the way to go.
    They will last a lifetime if you follow the directions and do not over torque them.
    They wont leak either.
    #12
  13. bgoodsoil

    bgoodsoil Dare to be Stupid

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    ha!

    You can flatten the valve cover without too much hassle. Put 2 nuts on one stud and tighten them together. Use that like the head of a bolt and remove the studs.

    Tape a piece of fine sandpaper on a flat pane of glass and make circular motions with the valve cover. If the valve cover is warped you'll notice the high spots getting sanded first while the low spots aren't. Keep making circles til everything's shiny.

    I warped a valve cover in a crash once and that trick caused mine to seal back up. In your situation you're probably better off sticking with the double gaskets or a silicon gasket(no experience with those) because of the stud repair. If you've had repairs done to one of those studs I'd leave it alone.
    #13
  14. Rucksta

    Rucksta SS Blowhard

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    The L/R goes down. Whilst it will fit either way the angle of the fins looks wrong when the cover is upsidedown.
    #14
  15. Bigger Al

    Bigger Al Still a stupid tire guy

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    #15
  16. lkchris

    lkchris Albuquerque

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    ... or the effects of some dummy previous owner trying to pry the cover off after removing only the center nut.

    OE gaskets are "installed dry" because they are made with a built-on adhesive that will indeed stick them to the cylinder head. That is, put the side with lettering next to head.

    Silicone gaskets are a leaking solution, but they are a PITA to work with.

    You'll know you have the R cover on the left when you note the fins not parallel to the ground (not even close). And vice versa.
    #16
  17. AirScoop

    AirScoop Adventurer

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    Last update from me on this thread: turns out I still had a tiny leak even with the double gasket, so I removed the valve cover and rotated it so the "L" faced down. Took the bike for a ride and no more leak! I'm guessing the valve cover is warped in such a way as to not leak near the bottom when installed right side up. Left both gaskets in anyway.

    Thanks to all for your help and great ideas!

    Dave
    #17
  18. sigpe57

    sigpe57 Been here awhile

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    I'm going this route. with double gasket, it's not pouring out but still 3-5 drops after 3 hours. I will exchange the valve cover with Left/Right marking side down. How did anyone ever find out L/R should face down? Is it in the workshop manual?
    #18
  19. GCCR

    GCCR Been here awhile

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    Sometimes you just need to get your bike up temperature by riding it afterwards to let the gasket seal up well. A nice 10-15 mile run is good to stop lots of leaks. Works for me.
    #19
  20. ME 109

    ME 109 Long timer

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    Mine stopped leaking after I stopped giving a shit. Win/win
    Near time to check the clearances again tho dammit.
    #20