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Old 03-27-2010, 11:32 AM   #1
AirScoop OP
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airhead valve cover oil leak -- easy fix??

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?
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Old 03-27-2010, 12:04 PM   #2
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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
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Old 03-27-2010, 12:18 PM   #3
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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...
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Old 03-27-2010, 12:58 PM   #4
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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.
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Old 03-27-2010, 01:02 PM   #5
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How convenient! I happen to have two gaskets! I'll try it and report back.
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Old 03-27-2010, 03:39 PM   #6
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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?
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Old 03-27-2010, 04:27 PM   #7
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Quote:
Originally Posted by AirScoop
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?
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.
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Old 03-27-2010, 05:04 PM   #8
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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)?
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Old 03-27-2010, 08:04 PM   #9
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Quote:
Originally Posted by AirScoop
Is there a proper orientation ("L" up or down)?
The scraped side goes down.

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.
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Old 03-27-2010, 09:20 PM   #10
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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.
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Old 03-27-2010, 09:43 PM   #11
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Quote:
Originally Posted by bmwrench
You are experiencing the effect of a warped cylinder head. 81 on heads are prone to this....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.
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!
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Old 03-28-2010, 12:07 AM   #12
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Leaky valve cover fix

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.
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Old 03-28-2010, 07:43 AM   #13
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Quote:
The scraped side goes down.
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.
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Old 03-28-2010, 08:21 AM   #14
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Quote:
Originally Posted by AirScoop
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?
The L/R goes down. Whilst it will fit either way the angle of the fins looks wrong when the cover is upsidedown.
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Old 03-28-2010, 09:04 AM   #15
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I solved my leaking problem with these:

http://www.realgaskets.com/files/motorcycle.htm#bmw


Silicone is good!
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Bigger Al screwed with this post 12-06-2010 at 09:49 PM
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