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umjwh Offline OP
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Had this 72T completely rebuilt top to bottom by a professional english MC mechanic. I noticed during the 500mi of break-in the head gasket was weeping oil.
Took it back and the mechanic checked both the mating surfaces and then replaced the head gasket. Got it back put 130mi on it and its still weeping oil all it on the left side. What are my options here. This time have the head re-torqued and see if clears up or have the head removed and have its surface checked for flatness (warped). Did not have this problem before it was rebuilt. Was rebuilt for using oil excessively and a worn cam.

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3 things. oil can work up the threads of the outer studs and come out at the nut, seal the nut if that's the case.

To check flatness take the head and gasket off put bearing blue on the clean surface and fit with no gasket and see if its touching equally where it should if not too bad you may be able to sand the highs, that's what I do.

Use a smear of 3bond Supersealer on the annealed gasket. It's what is recommended to 2 strokes rather than surfacing. It's a type of silicon for engines, just a smear both sides.


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Presume you are using a copper head gasket. Be sure the gasket is annealed before putting it on. I use Gasket Eliminator around the pushrod opening and the exhaust drain holes both sides.
After you run it up to temperature then retorque the head once cooled. Once things settle, cool and contract the torque can be lost. Turn each fastener slightly loose then torque.

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Mark.Does crank case pressure cause the oil to migrate up the stud?? My 67 spitfire did that about 600 miles after restoration. I did seal the washer and it stopped. Just curious.

Last edited by PFribley; 07/28/22 1:18 am.
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I don't know PF, I'd say it's compression pushing across that tiny piece of gasket to the stud. There is always some oil in there and that's what pushes up. With a big bore there is even less seal before the stud. So I always seal the nut/washer on them.


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Thanks Mark.

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A drop of welseal on an annealed head gasket will cure it.

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Are you sure it's actually the head gasket leaking? The leak could be coming from a variety of sources including the rocker box studs and nuts.

I usually use fiber washers under the heads of the rocker box nuts. The engine steady mount on the front of the rocker box is also a common source of leaks, use fiber washers here too.

As already mentioned it's worth getting the barrel and head checked for flatness. Since the engine is already fitted I suppose you could find a suitably sized of glass and place it on the barrel and check for any distortion, if there is distortion you will need to remove the barrel and get the barrel skimmed flat and the heads as well by a machine shop.

Check for any leaks from the cylinder base area and also the timing cover. Although it seems unlikely, leaking oil can appear in odd places when riding since the wind blows it around.


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Yep, Gunner, always worth a good look. I replaced a 'leaking' G/box pinion seal at work once. Cleaned it off took it for a drive, still leaking! Moved the chairs forward and picked up the seeping oil container behind the seats and tightened the lid. It was dripping fair on the pinion seal out a little hole in the floor.


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The fitting for the top end oil feed can leak causing what appears to be a head gasket leak.

The head studs do seem to run a bit wet, most likely from oil migrating from the rockers, IMO.

The most likely culprit, IME, is the oil drain holes for the exhaust valve pockets. I use small O-rings in the holes in the head gasket and copper coat on the head gasket itself.


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The oil is definitely seeping out where the head and the cylinder jug meet. I am having the cylinder head removed again (3rd time since rebuilt), this time by a different mechanic who seems to know his stuff about these old engines. He has run across the head gasket weeping oil problem before. He' ll get the mating surfaces flat and install a new annealed gasket using copper spray. Now the fitting for the top end oil feed was leaking due the builder using an alloy washer for a seal. It did not work at all. Had to use a fiber washer to clear up that leak. I guess I will see what happens this time around with the head gasket. Thanks for the responses

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You should be able to fit the gasket dry and it seal fine if all else is well with the bike.

Also a lot of people will skim the head with no consideration that the barrel surface will be out of true also.


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