head gaskets

I have a 1976 850 commando. I have blown two fiber head gaskets, so I went to a solid copper one. The trouble with it is leaking oil on the outside and I think it is leaking on the inside of the cylinders. How do I stop the leaks? Is any body familiar with the proper way of annealing these copper gaskets? Thanks Jack

lengthy but how to's for annealing in this thread - trick is after annealing to re torch it after running a bit (50-100 miles) then again after about 500 - will be leakproof

http://www.audioworld.net/BSA/forum/ind ... opic=737.0

Might be worth a thin coat of Yamabond on each side. The stuff has worked wonders for me in other applications.

Or there are copper-based sprays for this application - Permatex, etc. I have a can on my garage shelf, haven't used it yet so I can't say more.

Good luck.

BTW, I believe Mike meant to say "re-torque" the head after the indicated mileages - not to remove the gasket and re-anneal ("torch") it! And if so, he's right....

If you've blown two fibre head gaskets of good known make there's an underlying problem. Warped head or barrel, re-torque not done correctly, tight threads and bolts etc..

Best of luck,
Cash

If the head or barrel is not flat, a copper head gasket will be worse than a fibre one, as they do not compress.
Heat the copper head gasket on a gas ring until glowing, then plunge into a bucket of cold water.

BrianK said:

BTW, I believe Mike meant to say "re-torque" the head after the indicated mileages - not to remove the gasket and re-anneal ("torch") it! And if so, he's right....

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yupper that's what i meant - secret is to get the gasket cherry red hot if you do have to re-anneal it - there is a copper spray head gasket sealer from Permatex that some hot rod'ers (motorcycle hot rod'ers too!) like to apply to a annealed gasket before assembly , and its ok, but i think if the gasket is reanneled properly it is unneccessary

I have used the Permatex copper based spray on a small diesel engine that was fitted with a copper gasket. It had a number of leakage problems (coolant, oil, compression!) and the spray did the trick. Of course that was ten years ago, the engine is still in service and I have no idea what it will be like if I ever try to take it apart.

Check the bolts going through the head and look how deep they go into the barrels. They could be bottoming. I use 5 Triumph head washers that are extra thick on the head bolts to ensure these do not bottom out. Mick Hemmings Engine rebuild Video states this as well if you are persistently blowing Head Gaskets on a Commando to check these bolts. My 2 cents worth.
Regards,
CNN
:mrgreen:

ludwig said:

nortons3 said:

I have a 1976 850 commando. I have blown two fiber head gaskets...

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can you be more specific ?
Did they just leak badly , loose compression between the cylinders , or did you actually blew out a piece of the gasket ?
Twice in a row ?? ..same piece ?
I would like to see a picture of these gaskets !
If this happened with a late type , flame ring head gasket , than , like Cash said , I'm afraid you have a different problem .

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Hi, Yes - The first gasket was the original one and it blew out the front of the right cylinder, replaced with another fiber gasket and it blew out the right side of the right cylinder,. The next gasket was a carbon one which looked klinda flimzy, it blew between the cylinders and a piece of the fire ring scored the left piston and cylinder, bored over .020, new pistons the works. The head was planed after the very first blow out of the orginal gasket and the barrels were checked for flatness,they were okay. So I went to a copper gasket. Never thought about checking the head bolts for bottoming out, I,ll do that. Thanks for the info!! Jack