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Compression testing


Simpleton7016

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Simpleton7016
I have about a dozen engines here that I want to test for compression. I understand that there is a tool that I screw into the spark plug hole and then try to jump the engines a few times. Question one: how may times do I need to turn the engine over to get a good reading? If I can't get it to spin using the starters / generators, will I get an accurate reading by spinning it by hand with a vice grips or other? Are there any pitfalls I should avoid? Do I need to fill them with oil? Are there any recommendations for a preferred compression testing tool? Oh, and thanks Bob for your time over here today.....it was enjoyable and did you notice that I raised the bikes higher in the rafters so that you won't bash your head a half dozen times? :D
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Erik, compression gauge can be had for less then $25, that is the tool and something handy to have. Screws into spark plug hole. http://cgi.ebay.com/ebaymotors/SMALL-ENGINE-TRACTOR-LAWN-MOWER-COMPRESSION-TESTER-KIT_W0QQitemZ190287160609QQcmdZViewItemQQimsxZ20090215?IMSfp=TL0902151410004r22232 You keep spinning engine until highest pressure is encountered, not more then a half dozen turns. Anything above 80 psi is adequate. You do it with cylinder bore dry and engine at ambient temperatures. Engine needs to be turned over smartly, so vise grips won't hack it. The motors we bench tested today will do the job. The Briggs engines can be spun CW facing the fan (flywheel) and the Kohlers need to spun CCW so the compression release is disabled.
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Please don't forget that some of our engines have unloading devices incorporated into them. You will not get an accurate reading (will read low)XX( until you reach an RPM that disables the unloader. Take care, Chris
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