920 head gasket issues

Ladies,

How difficult is it really to have an oil tight head gasket seal on a 920 Commando? I am specifically thinking here of the purpose made Maney blocks, not a bored out stock block.

Can Maney 920 owners please share their experiences and tips / tricks for successful sealing?

I am often to be found contemplating going the 920 route (it is difficult not to be interested in increasing the capacity and reducing the weight in one move), but I do not want to end up with a leaky, maintenance heavy nightmare!

Thoughts and opinions, for and against, would be greatly appreciated...

Eddie,
My 920 has a Maney barrel. This was something which concerned me when I was building the engine as the liners protrude approx. .003" above the deck of the ally cylinder muff. The first attempt using .005" copper wire as per JS Motosports was a failure. Just too fiddley. I tried coating the annealed copper gasket with Wellseal. This was okay for 1,000 miles & then started to leak around the pushrod area. My next attempt was using a fine bead of Victor Reinz grey silicone rubber around both sides of the pushrod bores & oil return hole. This seemed to work much better, 3,000 miles, until the stupid 3/8" BSF studs started to pull out. I have sorted this with large inserts & refitted the head using the same copper head gasket & Reinz gasket. This is available from Motobins, the BMW parts people in Lincs. It is a very rigid type of silicone. Also what you will notice is that the copper gasket gets indented by the liners so it should in theory seal the whole joint. Steve told me he uses a Permatex product called the right stuff. I may try this if it leaks again.
Martyn.

Matchless said:

Eddie,
My 920 has a Maney barrel. This was something which concerned me when I was building the engine as the liners protrude approx. .003" above the deck of the ally cylinder muff. The first attempt using .005" copper wire as per JS Motosports was a failure. Just too fiddley. I tried coating the annealed copper gasket with Wellseal. This was okay for 1,000 miles & then started to leak around the pushrod area. My next attempt was using a fine bead of Victor Reinz grey silicone rubber around both sides of the pushrod bores & oil return hole. This seemed to work much better, 3,000 miles, until the stupid 3/8" BSF studs started to pull out. I have sorted this with large inserts & refitted the head using the same copper head gasket & Reinz gasket. This is available from Motobins, the BMW parts people in Lincs. It is a very rigid type of silicone. Also what you will notice is that the copper gasket gets indented by the liners so it should in theory seal the whole joint. Steve told me he uses a Permatex product called the right stuff. I may try this if it leaks again.
Martyn.

Click to expand...

Use contact adhesive and the installation of the .005" copper wire will not be "fiddley" - apply the rubber adhesive and let it dry until its tacky. Then the wire is easy to apply - simply lay it down – pressing it with your fingertip. It stays in place and won't spring up. Cut it after its in place and give it another coat of glue. FORGET WELLSEAL OR OTHER FANCY SEALERS. THEY WILL ALL FAIL. THE COPPER WIRE IS THE ONLY SOLUTION THAT WORKS. Take the time to do it right as per the instructions - its not rocket science and its worth the effort to have an oil tight motor. See instructions below and visit the other thread in this forum - "glue for JS gasket rings in england". Use "gasgacinch" if you’re not sure about which contact adhesive to use.

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INSTRUCTIONS
To prevent oil leaks, apply rubber contact adhesive around the pushrod tunnels and oil return hole, then lay down a loop of copper wire - crossing over the ends of the threads as in the photos – then cut it to length. Put rubber contact cement on both sides of the head gasket (Pliobond #25, Gasgacinch, Barge, Weldwood or any good yellow/brown contact adhesive). In cases where the pushrod tunnels are badly mismatched you must string the wire all the way around the front studs and use aluminum washers on the front stud nuts to prevent leaks. Use sealer on the threads in the cylinders near the pushrod tunnels so oil won't leak through the studs.

Glue the gasket to the head so the wire is safely covered and won’t be disturbed on assembly. With pistons at top, bring the head into position, tilt it backwards, insert and hold the pushrods all the way into the head and hold them in place with a helper or rubber bands before bringing the head down. Re-torque bolts after the first heat cycle.

SEE PHOTOS BELOW

This photo is only for the .003" thin copper gasket ring.



For all copper gaskets



For regular shaped copper gaskets


Note that I suggest "any good contact adhesive" - its the copper gasket and wire that you depend on - not the sealer. The wire crushes, spreads a bit and the gaps are filled. I started out this technique with no sealer and a tiny machined groove in the cylinder for the wire. Its the only technique that was 100% reliable in my racing days (when even composite gaskets failed).

Matchless - see photo below of "the right stuff" that you mention in your post. I've already tried this around the pushrod tunnels and it failed. So will firmer silicon sealers - They have them available for auto head gaskets and I've already tried them - all failures.

If you are interested in heading off on a silicone sealant tangent read on, but be advised that this post has nothing to do with how to cure oil leaks, but rather is intended to inform the reader about variations in silicone sealants we may encounter in our various mechanical endeavors. The post also relates to a comment Eddie made about sourcing sealers by brand in the following topic.

http://www.accessnorton.com/glue-for-gasket-rings-england-t24404.html

“It depends Jim. Many things from, engine oils to paint, are actually totally different compositions in different countries even if the label says the same!“

Click to expand...

It would not be unreasonable for an average end-user to assume that when he buys the same brand sealant product that varies only in color or slight difference in name that it would be very similar if not the same product. But as Eddie points out, caveat emptor.

Thus on the subject of silicone sealants/gasket makers just wanted to tie this into the above comment regarding differences between products, while keeping Matchless’ comment about the

“Victor Reinz grey silicone rubber” and “It is a very rigid type of silicone”

Click to expand...

and the Maney comment about a

”Permatex product called the Right Stuff”

Click to expand...

, passed along to Matchless, in mind.

Case in point might be the following table showing the physical properties of Permatex brand oxime-cure silicone RTV sealant/gasket makers (data from Permatex technical data sheets). One might assume at the outset that Ultra Blue and Ultra Grey might differ only in color, or that Right Stuff Grey might be about the same product as Right Stuff Grey 1 Minute. Well, they are certainly not! Right Stuff Grey 1 Minute has only 30% the elongation of Right Stuff Grey and yet has 2.4X greater tensile strength.


The Shore A hardness is affected by the crosslink density of the cured sealant and the filler type and filler loading employed. Generally speaking, and all other things being equal, the higher the x-link density the lower the elongation and the higher the tensile strength. X-link density is inversely proportional to swelling (the more x-linked the better the swelling resistance), so it would be reasonable to assume that Right Stuff 1 Minute Grey would likely have the best swelling resistance of the products listed. The foregoing observation is provided as informational only, since any of these products would provide excellent oil resistance which is the topic related to our discussion here.

In light of the above perhaps you'll be better informed (or more confused) the next time you seek a silicone sealant for a project.

Hi Nigel, you already know that my 920 has tended to suffer from a very small weep on the copper head gasket, mainly from the push rod area. It's never more than that...... a weep. It doesn't go everywhere but nevertheless is annoying, resulting in the odd strategic wipe with a cloth.

I've only done 200 miles this year since it's been put back together. This time I've used Wellseal on the annealed gasket and up to now all is bone dry, but based on the experience of Matchless it may not last. I'll have done another 2500 miles by the end of May, if all is dry I'll let you know.

Reggie.

As I have quite a few bikes on the road at any one time it may be a few months until I can report back. If the Reinz silicone fails as Jim seems to think, then I will try with the .005" copper wire. Either way I will let you know.

In using the copper wire, do you need this in place both sides of the head gasket?

Foxy said:

In using the copper wire, do you need this in place both sides of the head gasket?

Click to expand...

I don't think you need the .005" copper wire on both sides. What the wire does is crush and make a dent in the copper gasket. This adds a little tension on both sides of the gasket where you need it most - around the pushrod tunnels and the oil return hole. The tension seems to stay there because no leak appears later on.

Its probably overkill to add wire on both sides. No one who has done this correctly with one wire loop glued to just the head has ever complained to me about a leak.

About silicone - it does not adhere to metal as well as contact adhesive. The contact adhesive hardens somewhat but not too much whereas silicon stays soft and can worm out. A simple scratch test with a fingernail will show the difference. You don't have to worry about the contact adhesive getting too thick and it will always crush out perfectly flat even if dry when used on a head. It cooks a little in the head and darkens but it doesn't lose its integrity. With the thin .003" gasket ring it holds everything in place - but you've got to lay it down carefully and correctly in place 1st try.

With my tests I have used the contact adhesive between each surface - letting it dry enough so it won't lift when you touch it. And its no big deal to remove when it time to disassemble/reassemble.