Valve Cover Gaskets not sealing

[Bluethumb]

I recently picked up a 1983 R80ST, 44k and strong mechanically. When I got it home I started on a typical tune-up, torque heads, adjust valves, sync carbs, etc. In pulling off the valve covers I discovered two sets of gaskets on each side with gasket sealer. I pulled the gaskets off and cleaned the surfaces on the heads and valve covers. When I put the covers back on with new BMW gaskets, oil seeped out, a fair amount. I took the covers off and flattened the mating surface of each valve cover using a precision granite slab, remounted with Real gaskets, silicon rubber. Although far better I still had some leaks on both sides, a few drips. So I removed the covers and checked the mating surface of the heads with a precision straightedge and was surprised to see both a high point where the center stud is as well as some gaps around the outer mating surface. I then took the valve cover w/o a gasket and mounted it and checked for tightness and discovered that the cover rocks back and forth fron the high point in the middle, plus gaps around the mating surface.

Looking into the spark plug hole with a flashlight, turning over the engine, the valves look great and the dome of the position has very little carbon build up. The cylinder walls look great.

I know there's a thread about Real gaskets, but I used them for years on my previous airheads and they worked great. With this bike I bought a set thinking they would seal better then paper gaskets. They do seal better, but there's still a problem.

My plan now is to pull the heads, removes the valves and valve springs, and flatten the surface of the heads as I did the valve covers. I use wet/dry paper on top of the granite slab.

Two questions. Is it unusual for the mating surface of the heads to be so irregular?

And, is my plan a good one?

[Biebs]

Sounds like a plan - but wouldn't a little gasket maker in a tube cure the problem until head work was needed??


But to each his own and I commend you for your option of doing it right so any future owner will not have to deal with this problem.

[disston]

I think it's a little unusual but not unheard of to have this problem. Have heard of others with the same amount of warpage. Now you know why the PO had two gaskets. Your plan sounds sane to me. It should work.

I'm the guy with the other thread and I'm about to go back to OEM gaskets. One more chance though, I'm going to try putting it together clean and dry.

[Bluethumb]

If you need a set of stock gaskets, let me know. I have a couple of extra sets.

I have been told that the mating surfaces should be somewhat rough, not polished smooth, or the gasket will not grip. Probably more critical with the silicon gaskets.

[Patrick M]

I have a lot of success using Loctite 518 with issues like this. Using it in conjuction with the gasket yields good results. It's unlike RTV or silicone gasket makers. It also doesn't make a mess if you apply too much. A little goes a long way. I used to use it on intake manifolds and valve covers of inline Hondas.

http://www.summitracing.com/search/p...c-gasket-maker

[bmwhacker]

I ended up using two gaskets on each side on my R100s engine...no sealant. Don't like using sealant as valve cover removal seems to be a frequent event in my world. Maybe not a proper fix but they don't leak anymore.

[Bluethumb]

I'm not too keen on using any type of gasket sealer. The idea of having to scrap it off and renew every 5k when I check the valves would drive me insane.

Today I'm going to give the surface of the heads a careful evaluation plus a friend is coming over to help me puzzle it out. At this point I'm looking to take the jump and pull the heads and flatten the mating surface.

It means the expense of new gaskets plus time involved, but at least it will be done right. Hopefully!

[Stan_R80/7]

I had a valve cover leak on the left cylinder on my '78. Eventually, I took the valve cover off and used marking compound (actually, $1.00 purple lipstick) to located the high spots on the head. The valve cover was subsequently sanded at those locations. Taking the heads off and removing material is an option, but not a good idea.

After about four iterations of marking and sanding the covers - then repeating - the marking pattern was more uniform. The leak still existed after the valve covers (using silicon gaskets) were reinstalled. It turns out the leak was from the pushrod tubes in the head.

The head must be 250 deg. F to move the tubes or the head will be damaged. So, after the engine was hot (and using an IR temperature meter) the valve covers, rocker arms, and pushrods were removed and the tubes tapped back into the head. Another option is to remove, degrease, clean the head then put it in a (calibrated) 250 deg F oven before moving the pushrod tubes.

My point is to make sure the leak is from the valve covers. Degreasing and cleaning the cylinders then dusting with talc (baby powder) is a good way to find such leaks. Good luck!

[hardwaregrrl]

Could try a combination oem gasket and a Real Gasket. Maybe stock on the cover and real on the head.

[lkchris]

Lots of times the sealing surfaces are damaged by guys using a screwdriver trying to pry the cover off after only taking off the center nut---that is, failing to discover the two small nuts at the ends.

In any case silicone gaskets are a pretty good "crutch" when sealing surfaces aren't perfect.

With good sealing surfaces and properly installed, OE gaskets can be leak free for a decade or more. No "goop" required, as the printed side of the gasket has factory-applied sealant and obviously goes against the head.

[kaput13]

If your 83 still has the emissions plumbing (and it is not illegal in your state) you might want to consider removing and replacing it with the BMW plugs. Some have speculated that the smog equipment increased head temperatures and led to warped heads. I had this problem, tried the double gasket, sillicone gasket etc to no avail and eventually had the heads milled. Good luck with it.

[DoktorT]

Originally Posted by Bluethumb

I'm not too keen on using any type of gasket sealer. The idea of having to scrap it off and renew every 5k when I check the valves would drive me insane.

Today I'm going to give the surface of the heads a careful evaluation plus a friend is coming over to help me puzzle it out. At this point I'm looking to take the jump and pull the heads and flatten the mating surface.

It means the expense of new gaskets plus time involved, but at least it will be done right. Hopefully!

No reason you can't do the job in situ with a big flat file, well, not a file but a heavy tooth rasp so as not to clog the file teeth. Just pull the center stud then work your way around the perimeter. The high and low points will show themselves immediatly. Follow up with finer abrasives wrapped around the file.

You must take great care not to nick the valve springs, and for sure you must stuff the tube holes with something so you can do the final cleaning without swarf getting into the crankcase.

If you have the time and patience and take great care, it can be done this way.

The covers are easy. Just remove the two studs and work it on a flat surface with a series of abrasives course to fine. Flat matte finish is spec.

[Airhead Wrangler]

Originally Posted by DoktorT

No reason you can't do the job in situ with a big flat file, well, not a file but a heavy tooth rasp so as not to clog the file teeth.

I like a good flat dressing stone for this. Just make some light swipes with it laying flat on the mating surface and any high spots are gone. Try to make your strokes in the same direction as the mating surface to leave striations that are parallel with the direction of the mating surface as this also helps sealing. As mentioned take precautions to not get swarf in the bottom end. Or you could just half-ass it with lots of silicone until the next time you pull the top end and then do it right on a flat stone.

[robtg]

Why not do it right and send them to a machine shop, mill the top parallel to the bottom like they are supposed to be?

[disston]

Originally Posted by robtg

Why not do it right and send them to a machine shop, mill the top parallel to the bottom like they are supposed to be?

Since he's taking them apart anyway to do the lapping this would really make sense, if it cost, what, $10 each side. Or a little more. But how much should this cost? In today's World it might be more than I would think reasonable.

I'd take them to your machinist buddie and find out.