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TOPIC: Sticking or burn exhaust valve

Sticking or burn exhaust valve 6 years 10 months ago #45297

  • BADBAJA
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Just did a compression check. Not sure the cylinder number (top cylinder). The numbers from top to bottom are 80
180
180
190
Then I did leak down check and air blows out the exhaust of the same cylinder. Just wondering what could help dislodge the exhaust valve as a first step before any tear down?

Thant you.

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Re: Sticking or burn exhaust valve 6 years 9 months ago #45305

  • billr
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Do you have a service manual and Illustrated Parts List?
Pull the valve cover and rotate engine to TDC on that low cylinder, is there clearance between the cam follower and the cam lobe? If you have valve seat recession then the valve might be held open. I've seen this several times, resetting clearances solved the problem. Those other cylinders are like new. Hope you get lucky.
Debris on valve might be causing it too, seen that even more.

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Re: Sticking or burn exhaust valve 6 years 9 months ago #45317

  • BADBAJA
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Check my last post. Thank you again.

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Re: Sticking or burn exhaust valve 6 years 9 months ago #45319

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I dont know why it didn't post. Sorry getting used to iPhone posting.

I can see the back of the valve through the plug hole and it looks out of shape. Like a chunk missing from the back edge of where it seats. Just don't have the funds to do a bunch of work. Anyone have any ideas ?

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Re: Sticking or burn exhaust valve 6 years 9 months ago #45391

  • 4stroke
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Unfortunately with a mechanical failure there is no quick fix solution. The most economical fix would be to replace only that bad valve. Considering the compression readings in the other three cylinders you could leave them undisturbed but you will have to teardown the engine to replace the valve in the bad cylinder. I have two early powerheads here, both with bad exhaust valves in one cylinder. One of them I can also see a piece missing on the seating surface of the valve. These will eventually be torn down and the valves replaced.

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Dick Johnson

1989 16ft Sylvan

'57 Evinrude 18 (finally found a decent one)
'58 Johnson 5.5
'72 Johnson 6.0
'61 Homelite
'64 Johnson 18
'65 Homelite 55
'66 Homelite 55
'68 Bearcat 55 (3)
'70 Bearcat 55 (2)
'71 Bearcat 85 (Sold)
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