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Compression Tester - Necessity Or Waste Of Money?


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#1 New.Canadian.DB.Owner ONLINE  

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Posted October 13, 2012 - 03:19 PM

I've never owned one, but lately they seem to be on sale everywhere i go. Do you folks every use them & if so how often & for what?

#2 ol' stonebreaker OFFLINE  

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Posted October 13, 2012 - 03:44 PM

If you have a compression problem a comp. tester can tell you if it's rings or valves by first running a "dry" compression test then a "wet" test by squirting some motor oil,a tablespoon, in the cyl via the spark plug hole prior to the wet test. If the wet test reads higher the rings are worn too far. No change if it's a valve. Normally you can hear a bad valve thru the intake w/ filter removed or in some cases, the intake snorkel off the carb or thru open exhaust while turning engine slowly by hand.
HTH,

Mike
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#3 Grumpy OFFLINE  

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Posted October 13, 2012 - 04:16 PM

Most GT engines have a compression release, and it hard to get a good compression reading
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#4 ol' stonebreaker OFFLINE  

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Posted October 13, 2012 - 04:41 PM

Most GT engines have a compression release, and it hard to get a good compression reading


I've wondered why the mfgrs didn't just buy a stronger starter motor, would seem cheaper and take a lot less engineering/designing/testing. Maybe the average consumer is getting too wimpy to pull a starter rope,LOL!!!
Mike
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#5 HDWildBill ONLINE  

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Posted October 13, 2012 - 05:04 PM

I use one quite often, but I deal with quite a few engines. Like mia2ofus said it can tell you about the internal shape of the engine. If you only have one or maybe two GT's then you probably don't need one and if the occasion should arise that you need one go rent one from Advance.
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#6 JDBrian OFFLINE  

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Posted October 13, 2012 - 05:11 PM

I picked up a nice one at a yard sale last summer. A MAC and I got it cheap enough for it to earn it's keep. It's a quick way to do a basic check on an engine. I used it on a little tiller I bought with a 3.5hp Tecumseh.
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#7 New.Canadian.DB.Owner ONLINE  

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Posted October 13, 2012 - 05:46 PM

Thanks to everyone who weighed in on this topic. You pretty much confirmed what I thought. Those who need them, need them. I can likely survive without one because I have until now. I'll get one when I need it.

#8 JDBrian OFFLINE  

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Posted October 14, 2012 - 06:15 AM

If an engine is totally without compression you can tell by pulling the cord or rolling it over by hand. I had this happen on an MF8. Stuck valve! It's more of a quick, easy way to access the basic health of an engine. Not a necessity to have one but handy to have IMO.
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#9 ol' stonebreaker OFFLINE  

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Posted October 29, 2012 - 09:11 AM

After receiving the shop manual for my JD 314 I was going thru it and it explained how to run a compession test on engines w/ comp release. Screw a bolt in one of the holes in the PTO pulley, engage clutch, anchor rope on the bolt, wrap rope around pulley so it turns the engine backwards when pulled. News to me.
Mike
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