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Leaky Seagull

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Leaky Seagull

Post  Mike Neden on Mon Jul 24, 2017 7:19 pm

Hi

I'm having an issue the engine losing compression through the head joint when it warms up. It will run for about half a mile and then packs up. The head seems flat although there was some pitting on the outer joint (head joint is stepped), which I have now taken off with some 800 grit taped to a glass plate. What torque should I tighten it up to? I'd previously just tightened it as much as I could with a spanner. There may be a photo of the head attached, but probably not.

Cheers

Mike



[url=https://servimg.com/view/19733473/7][img]https://i11.servimg.com/u/f11/19


Last edited by Mike Neden on Wed Jul 26, 2017 6:43 pm; edited 1 time in total

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Leakygull

Post  keith.hodgenia on Tue Jul 25, 2017 6:44 pm

When new there was a narrow lip on the top of cylinder, if this has been ground away over the years it is difficult to exert enough seating pressure via the head bolts. Possibly you could machine a new ring if there is enough metal there.

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Re: Leaky Seagull

Post  banjo boy on Tue Jul 25, 2017 8:07 pm

When the head is on and tighten down can you get a feeler gauge between the head and barrel to check to see if it sitting flat and not bottoming out, just a thought but I don't no nothing of these engines.
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Re: Leaky Seagull

Post  Mike Neden on Wed Jul 26, 2017 7:09 pm

Thanks for the feedback. With the head on there is a consistent approx. 0.15mm gap, so it is only sealing on the top of the lip I.e. the inner of the two faces on the many photos. Any ideas? I have some shimming copper which is 0.2mm thick, so I could make a gasket for the outer face?

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Mike Neden

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Head sealing

Post  piston 197 on Thu Jul 27, 2017 5:59 am

You would be better to make a copper ring that sits on the inner face, as this is what forms the seal against the lip of the barrel, looking at your pictures it would seem the worn part is the inner ring particularly at the "shallow" end of the compression dome, alternatively you could machine perhaps 25 thou off the inner face and the same amount off the outer face to bring the faces back to their relevant differences and have both faces flat ?
When tightening ensure bolts are tightened a turn at a time in clockwise rotation once starting to pinch up .
JH
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Re: Leaky Seagull

Post  Mike Neden on Thu Jul 27, 2017 6:34 am

Thanks John

I did quickly make up a gasket up for the outer face and I'll give it a go, but a putting a gasket on the inner face wasn't a success (I seem to have missed this part of the story out). Fingers crossed, but I can see me having to get it machined down as you suggest.

Out of interest this is the project bike you sold to a bloke called Derek a few years ago.

Ta

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sealing face

Post  piston 197 on Thu Jul 27, 2017 6:44 am

Good to know it has been taken on !
It is the inner face that does the sealing so there must be some wear/corrosion either on the top of the barrel lip, or on the inner face itself, the outer face should not locate on the cylinder, there should be a gap there, maybe sealing this gap will make a temporary repair, but there will be gas leakage in the gap between the inner face and cylinder lip and will cause it to burn away further.

Years ago my friend Ritchie did a similar thing with his iron head Triumph, the gas leakage caused his cylinder stud to burn away and weld itself to the head and cylinder, he had to destroy the cylinder head to get it off !
Sounds like a skim of the top of the barrel to restore the lip and a skim of the inner and outer surface of the head will be the best option for a permanent repair ?

JH
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Leakygull

Post  keith.hodgenia on Thu Jul 27, 2017 9:06 am

I had a similar problem on my iron head 350 ariel, these engines don't have head gaskets either. I tried a ring of shim copper, it worked for a while. In the end the top of the barrel was ground to restore the thin contact patch. No problems since.
Retightening the head bolts when the engine is hot might help but beware something might give way as the engine cools.

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Re: Leaky Seagull

Post  Mike Neden on Sat Jul 29, 2017 12:11 pm

Thanks for the feedback

The gasket didn't work so I have stripped it down again. Photos of top of barrel below. I don't think it looks great.  Any comments?

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Re: Leaky Seagull

Post  Graham M on Sat Jul 29, 2017 12:34 pm

Does it have a decompressor and if so could that be the cause?
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Re: Leaky Seagull

Post  Mike Neden on Sat Jul 29, 2017 5:06 pm

It does Graham, but it seems to function fine. You will note from the photo that mine also has the tickler on the wrong side.

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Not so leaky Seagull

Post  Mike Neden on Sun Jul 30, 2017 6:39 pm

Anyway, I took a chance and lapped the head and barrel using valve grinding paste (fine) and it seems to have done the trick.  The top lip of the barrel isn't perfect but, after half and hour of grinding, I'd lost the will to live.  Thanks for all the input.



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Re: Leaky Seagull

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