valve covers mystery leak: time for new gaskets?

[darkonaut]

i installed r1200c valve covers on my '99. they were stripped and powdercoated, then the mating surface was sanded flat. the left side is working great, but the right side leaves a film of oily oil on the underside of the head after even a 10-minute ride. i re-sanded it flat(ter?) on a piece of granite countertop and no dice, still leaky.

what should my next step be?

new gaskets? (current are original afaik - 40k but stored outside now and previously)

there is a miniscule misalignment such that the gasket contacts the head on the gasket's entire mating surface, but contacts the valve cover fully on only two of the three sealing ribs along the bottom edge, i.e. the valve cover is being held slightly too high. what do you think about grinding a tiny bit (<1mm) off the top of each bolt hole to oval the holes slightly and move the cover down?

try new gaskets first i assume? does this look like a bad inner or bad outer seal?











lookin' good in the neighborhood:

[sgoodwin]

New gaskets first, then see if you still have a problem.

[darkonaut]

just replaced the inner gasket and, still, no dice. dunno how oil would be getting next to the intake port if something weren't going wrong at that seal.

[iminspaaace]

Why not replace both? If the outer gasket has swollen or some other geometric issue that would cause the inner gasket not to seat properly, causing a leak there.

Also, aren't you supposed to change gaskets every time you do a valve adjust? That's what I do anyway... maybe I'm throwing my money away, but it's cheap insurance from my perspective.

[brentw1]

unless they are damaged Ive never had one leak or require replacing, you are wastig your money.
if you remove material from the mating surface you will reduce the pinch on the gasket,
the bolts tigthen to the stops and provide the same lenght.
so whatever you have removed has increased the gap between the head and cover.
try putting in new seals behind the bolts and see if it pinches the gasket more than the worn ones.
also check that the leak is from the valve cover, I assume you did the plug gasket,
it could be from any of the hardware in the timming cover, like the timing guide bolts which
have a aluminum crush washer seal, tensioners etc.

[darkonaut]

yeah, the new gasket was noticeably softer than the 19-year-old (?) old one, but the left side has the same age (?) gasket and isn't leaking.

i am gonna try the bolt-hole mod tomorrow morning. there is a noticeable misalignment when you peer into the plug well with the plug wire out and valve cover on, probably the same ~1mm difference as on the outer mating surface. if nothing else it'll make me feel better about that not being the problem.

if that doesn't work, then new outer gasket. it was working fine with the old valve cover last week

brent, i was thinking about "running out of pinch" while sanding. i kind of doubt that's what's up, just because the outer gasket looks "equally pinched" on both sides and i used only 800-grit, 1500-grit, green scotchbrite, and paper towels. what about adding the thinnest possible washer under the bolt head and over the existing metal washer? the rubber pieces always get jammed into the bolt holes pretty well so i think there's enough "outward pinch" on the tapered part under the bolt head.

[brentw1]

I would assemble it without the gasket and see what the alignment is before I made the
holes larger which could let the bolt holes leak,
it is for the correct side I think there are left and right ones.
the bolts are tapered at the stem so you would need a larger washer

[nrpetersen]

You'd have to sand for three weeks to take off more than a couple of thousands of metal.

Your best bet is to use red silicon rubber "Real Gaskets" , which I presume you are using now, and then wipe the seal surfaces with a thin wipe of aviation "Fuel Lube", which is a clear non-hardening sealer - sort of like Permatex except completely clear and non-hardening.

You may have to wash things down a couple of times after assembly to get rid of the last of the so-called tramp oil that mysteriously comes out of nowhere.

[darkonaut]

tentatively FIXED!

i think brent wins this one.

when i took out the plug wire, the inner part was oily and there was oil in the plug well. decided to fix the inner seal before trying anything that would change the outer seal.

what i didn't think was important, but then thought about: when i got them back from the powdercoater, i thought the inner seal surface on the valve cover had to be smooth-machined like the outer surface, and there was some powdercoat there. i mentioned this to the coater and he...just sanded the coating off. that, plus the fact that the cover originally had a chrome layer there, seems to have taken just enough off the surface to let the inner seal weep. the oil on the bottom of the head must have gotten blown through the head (there is an air passage between the top and bottom valves; you can see the spark plug from both sides when the plug wire is out) and trickled down the back of the head onto the bottom. that's why there was oil next to the intake boot but also under the head but also splattered everywhere behind.

took a washer from an old concours steering head and ground it to size, about 1-1.5mm thick, inner diameter just large enough for the plug wire to fit through, outer diameter just small enough to fit inside the lip on the outside (valve cover side) of the inner seal, and used it as a spacer to press the seal more firmly against the head.

looks good after the same ride that was making it leak before...

tl;dr the inner seal really needs to be squished, probably more than the outer seal, and a smooth surface is less important than a good squish. it's soft rubber vs. a "hard seal" like the shaft seals and, i think, the outer valve cover seal.

thanks everyone

[tomvv11]

On a general valve cover note, they really do like to be torqued to the manual's spec. My first S's PO had overtightened one of the valve cover bolts and stripped the female thread in the head. The subsequent Helicoil/JB Weld repair that I inherited never got back to keeping 100% of the oil on the inside of the motorcycle. That .0000001% has special boot and pantleg-seeking abilities.