Uneven valvehead surface = leak

[Soeren]

After doing a valvejob and replacing an old white rubber gasket, I found that the surface on the rockerarm side (surface that matches up against the valve cover) is uneven and the new harder gasket from mobotins cannot be compressed enoguh to make a seal. It is so bad that I can easely get a feeler gauge in between the head and the gasket when the bolts are tightned down.

What is the best way to deal with this?

I have tryed to determin where the excess materiale is located by running the feeler gauge in the gap between the head and the cover, and took a file to it very gently. Should I continue filing or should it be disassembled and surfacegrinded?

[Tony Smith]

Needs to be properly skimmed flat, which you can only do after removign the cylinder heads and the "buttons" that locate the rocker gear.

Best approach is to use two gaskets until such time in the future as you have to take the heads off, then have them done.


The No.1 cause of warped gasket mating surface is over tightened nuts. The centre nut should be tightened just enough onto a wave washer so that it does not undo. The M6 nuts should be fastened onto serrated washers and again just tight enough so they do not undo.

I know someone whose center nuts have not been fitted since 1981, their rocker covers do not leak

[Barry]

The centre nut should be tightened just enough onto a wave washer so that it does not undo. The M6 nuts should be fastened onto serrated washers and again just tight enough so they do not undo.

I do mine like that and it never leaks a drop.   They were like that when I bought the bike which told me something good about the previous owner.

[BPT]

What do you all consider the "serrated":washer?  There's the one that looks flat and even but with the slightly raised grooves or the other type that feels sharp and spiky (I've always called it a "star" washer).  Is it one of these?

[BPT]

Or this:

[skippyc]

did you check the rocker covers on a glass surface with fine emery paper, do some figure 8s and check the surface it will show you if it is bent. I use this method to resurface my BSA parts.

[mrclubike]

silicone gaskets

After you get everything flat again go back to standard gaskets

[Tony Smith]

Or this:

I use this type mainly because the first type you pictured are too damn hard to find. Even no washer at all works, as mentioned previously the trick is to not get ito a contest of wills with them, the serrated, stirated or wave washers merely make that job easier.

[Soeren]

The centre nut should be tightened just enough onto a wave washer so that it does not undo. The M6 nuts should be fastened onto serrated washers and again just tight enough so they do not undo.

I do mine like that and it never leaks a drop.   They were like that when I bought the bike which told me something good about the previous owner.

Totally opposite in my case, everything is tightend down by gorilla, and it pains me everytime I loosen a new bolt on the bike and it is waaay over tightend.


I'll try to locate some silicone gaskets (any EU dealers?) and make a full repair when its off season.

[Matt Chapter]

Get the thick silicone gaskets, swap em out, go for a ride.

I don't have center nuts, wish I had put washers on when I replaced them after losing them the first time.

[georgesgiralt]

If you can't find silicone gaskets, another solution is to put 2 OEM gaskets on the job.
Put some sealant between the two. I used this a long time until I found a less warped valve cover.

[jamo]

Just to say about the locking washers pictures
The first is called a Nord Lock a German design the picture shows it after use, when new it is bonded together. It can be used again if you use both halfs with the larger ratchet together. I use them on ancillary fixings on steam turbines.
The second is an external star washer they also come as an internal star as well. The other locking washeris a spring washers all should be used with a flat washer underneath to prevent damage to the parent metal. Just my ideas

[jamo]

Just to say about the locking washers pictures
The first is called a Nord Lock a German design the picture shows it after use, when new it is bonded together. It can be used again if you use both halfs with the larger ratchet together. I use them on ancillary fixings on steam turbines.
The second is an external star washer they also come as an internal star as well. The other locking washeris a spring washers all should be used with a flat washer underneath to prevent damage to the parent metal. Just my ideas