Scoring or head gasket? Force 50- 1986

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bioman

Seaman Apprentice
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Jun 28, 2004
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35
Engine very weak. Pulled head.
Top cylinder (140) thick black carbon, dry. cylinder looks good, but piston looks deformed (melted?).
Lower cylinder (125) very clean (no carbon) but wet with oily residue. Piston top looks perfect. Cylinder walls show tiny diagonal scratches (?) at 10 and 2 o'clock. Is this scoring?
Oily residue collects under head. No obvious breaks in gasket, but... what would it look like w/ 125 lb pressure?
Eurolarva advise? Pics available if helpful
 
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steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Re: Scoring or head gasket? Force 50- 1986

Not an expert but the lower cylinder/piston seems too clean to me like there was no spark.Or possibly water getting in.Though the water could give a super clean plug and you may see some evidence of corrosion/rust on the plug.
Diagonal scratches may just be honeing marks or someone a little heavy handed with a previous inspection.
Upper cylinder sounds like it may have been running rich.clean it up good and look over the piston.open the exhaust cover and check the piston through the exhaust ports.Let us know what you find.
 
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bioman

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Jun 28, 2004
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Re: Scoring or head gasket? Force 50- 1986

Thanks Steele... did you see the part where I said the the top of piston looks melted/ deformed? I mean really deformed!
Also when I check the piston through the exhaust port, what am I looking for..broken rings?
Thanks for the help. Eurolarva where are you?
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Scoring or head gasket? Force 50- 1986

Unfortunately from your discription the piston is probably toast you may be able to confirm how bad it is
looking through the exhaust ports.
You looking for broken ring lands,scoring on the piston
evidence of blow by or melting/burning of the piston.
From the compression there probably isn't any blow by but maybe you can see if there is any melting or othe damage.If the piston looks pretty good other than the distortion you might consider running as is depending on
what you think of the rest of the motor.
Something caused the piston damage possibly running
a lot on one cylinder, kind of like lugging it.Or maybe the timing is off.
 
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bioman

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Jun 28, 2004
Messages
35
Re: Scoring or head gasket? Force 50- 1986

Thanks steele. Will do some checking and advise.
bioman
 
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