Compresion

Captin Dilly

Captin Dilly

Cadet
Joined
Aug 19, 2012
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11
I just did a compresion test on my 1989 Johnson 110 cylinders 1&2 are at 110 psi, 3&4 are at 120 psi. Is this a simple case of torgueing the head on 1&2 or am I looking at something more serious such as rings or worse? By the way...this forum has been such a huge help already, thanks in advance.

The Captain
 
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Daviet

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Sep 24, 2008
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8,958
Re: Compresion

As long as they are within 10% of each other I wouldn't worry about it. You might gain some by replacing the head gaskets.
 
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Daviet

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8,958
Re: Compresion

Correct plugs?
Carbs running rich?
Spark jump a 7/16" air gap and is it bright blue?
 
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Daviet

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8,958
Re: Compresion

Didn't say anything about overheating and running rough.
Check the spark and see if it is up to par.
It only runs rough when it overheats?
It is possiable to have a defective head gasket that allows compression into the cooling system, causing it to overheat, but still have acceptable compression.
Running rough when it over heats could be a coil breaking down when it gets hot, need to check spark when it is acting up.
BUT, you need to correct the overheating problem first so that you don't cause major problems.
 
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Daviet

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Sep 24, 2008
Messages
8,958
Re: Compresion

Several componets in your ignition system, go to the CDI website and look up your engine, use their troubleshooting guide to help you find your problem.
A quick check on the coils, swap the coil with no spark for a coil that does have good spark. If the no spark condition moves with the coil, you have a bad coil. If the no spark condition stays on the same cylinder, go to the CDI website.
 
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