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buddhabanshee

Compression test question

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Just did a compression test today. First cylinder was right around 130 psi and the second was 120. Should I be worried that they are that far off?

 

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First of all I would use a snap on comp tester because they give very accurate readings.Make sure gauge hose fitting is properly hand tightened so the rubber gasket makes a good seal. Also make sure your getting the engine up to operating temp and holding the throttle wide open while checking the compression. Keep kicking it over untill the needle stops moving on the gauge.....the readings on each cylinder shouldn't be more than a few psi difference from one another.

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Craftsman, mac, snap on I've had good luck with all of them. The harbor freight one I used gave me fucky readings that's why I asked.

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The motor was warm..at least for the 1st cylinder for sure...and had wide open throttle. Did the second cylinder twice making sure everything was tight and still got the same reading

 

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^^That

Rule of thumb on compression tests is no more than a 10% variation.

But try again, both cold.

And keep a close eye on it in the future, cause you are under the 10%, but pushing it.

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Ive ran a motor with 120 and 150 psi for a few more duning seasons like that. I wouldnt worry about 10% difference. Thats real world experience not technically by the book someone made up.

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How do I do a leak down test?

 

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80d200b41cdbb9bbff089bbf8338a635.jpg

 

Intake side looks like such and exhaust removed with exhaust plugged

 

 

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