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testing compression

jarhead's Avatar

Join Date: Jan 2006
Posts: 73

04-28-06, 01:06 PM   #1  
testing compression

What are the procedures for checking compression on small engines and what readings should be good, bad or in between.

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v8driver's Avatar

Join Date: Sep 2005
Posts: 767

04-28-06, 07:27 PM   #2  
Just use a good compression tester, 80 is usually around the lowest it should be (I've seen some lower and still run OK)

puey61's Avatar

Join Date: Apr 2004
Posts: 3,224

04-29-06, 07:18 AM   #3  
Not one engine manufacturer will list a compression value for any small engine due to the fact that 90% of all such engines have compression release mechanisms whereas at low rpm (cranking rpm's) one of the valves will open up slightly on the compression stroke to aid in the ease of start, by design. Based on my years in the business, 50psi is as low a number you'd like to see and 90psi is a good number.

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