Compression test

cc67

cc67

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When doing a compression test on an older motor that has been sitting for a while,is it a good idea to shoot a little bit of lubricant into the cylinders to simulate a functioning motor. I was thinking a dry cylinder might give a false reading.
 
HighTrim

HighTrim

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Re: Compression test

They call that a wet test, and usually increases compression, especially if there are ring issues. This of course depends on what motor we are talking about. I would add some oil , especially if the motor has been sitting. It is not seized is it? How long are we talking?
 
tashasdaddy

tashasdaddy

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Re: Compression test

what motor, always tell us what you are working on.
 
cc67

cc67

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Re: Compression test

No engine in particular. I am looking for an older evinrude 18 hp and was looking for a little advice. Would a lower "dry" reading nessasarily indicate a ring problem? I know in 4-stroke engines this is generally the case. But since oil is mixed with gas in a two stroke, I thought this would give a true reading.
 
jbjennings

jbjennings

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Re: Compression test

My advice--DO NOT get an older 18 hp johnson or evinrude, especially in the '57 or '58 models......They are really ugly and are absolute junk! They should all be gathered up and shipped to me so I can dispose of them properly..;)
JBJ
 
JB

JB

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Re: Compression test

Yup. And when JBJ has all he can handle send the rest to JB. :)
 
cc67

cc67

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Re: Compression test

I had a line on a 58 but the guy never sent me a picture and wanted $300. Gona look at 59 this afternoon. What should I look for as far as a compression reading?
 
tashasdaddy

tashasdaddy

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Re: Compression test

all compression guages are different, but over 100 psi, and with in 10% of each other.
 
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