Compression changes every time I check it.

[Pokertrampp]

1988 Johnson 120.

I have been having an issue with this motor for some time and I think I may have found the problem, but would like another opinion.

I checked the compression and I have 100+ on all cylinders so I figured I was ok. The motor continued to have a mis so I checked it again same readings.

I checked it a third time just for piece of mind and one cylinder was now down to 70 psi, so I checked yet again and now down to 50 psi, checked again now back up over 100+ psi.

I pulled the head gasket and all I see is one very small spot and I think the ring on the gasket should be a little thicker but I am not sure.

Has anyone ever heard or had a headgasket do that or is this from something else. Thanks Again

 

[jbjennings]

Re: Compression changes every time I check it.

I'd pretty much bet that your gauge is causing the difference.
JMO,
JBJ

 

[OldJohnson6hp]

Re: Compression changes every time I check it.

seems like a large variance gotta be the gauge

 

[Pokertrampp]

Re: Compression changes every time I check it.

I'd pretty much bet that your gauge is causing the difference.
JMO,
JBJ

That is something I forgot to mention, I tried 2 different gauges with the same variations. That was my first, thought that the gauge must be bad.

 

[Daviet]

Re: Compression changes every time I check it.

It sounds like you need another compression guage.
That head gasket does need to be replaced.

 

[Pokertrampp]

Re: Compression changes every time I check it.

It sounds like you need another compression guage.
That head gasket does need to be replaced.

I ordered the new gaskets, so I will know in a few days i suppose.

I attached a few photos of the head and cylinder(s) the head looks a little like it may have been steam cleaned but the cylinder does not, is this the case and is this normal looking or not.

 

[Craig-]

Re: Compression changes every time I check it.

Bad or missing O ring on gauges?

 

[83ebbtide]

Re: Compression changes every time I check it.

Cracked ring maybe? I'd say put it back together and see what you get on the readings. If they are still off try and borrow another tester.

What is the issue you've been having?

 

[F_R]

Re: Compression changes every time I check it.

Whoa, that steam cleaned one isn't normal. You may be getting water in that cylinder. The gauge is probably telling the truth. You need to do some more troubleshooting to see what is really going on.

 

[Pokertrampp]

Re: Compression changes every time I check it.

What is the issue you've been having?

Engine has a mis while running at any rpm

 

[Pokertrampp]

Re: Compression changes every time I check it.

delete

 

[Pokertrampp]

Re: Compression changes every time I check it.

Whoa, that steam cleaned one isn't normal. You may be getting water in that cylinder.

Thats what I was thinking, Thanks

 

[boobie]

Re: Compression changes every time I check it.

The head gasket for that cyl does't look that good either. Clean up all surfaces and install new gaskets.

 

[bkwapisz]

Re: Compression changes every time I check it.

The head gasket for that cyl does't look that good either. Clean up all surfaces and install new gaskets.

I agree. It looks in the pictures you posted like the spot on the head gasket correlates with the "steam cleaned" portion of the corresponding cylinder. I also agree with F_R that the clean combustion head is NOT normal. My bet is you have a head gasket leak. Replace that gasket since it's already off and make sure the mating surfaces are surgically clean.

Glad to hear you chased down your chargin issue. I was following that thread and used it to solve my own problem with everyone's help. Nice to go out and not worry about a dead battery, no?