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some people tell me that u tell if ur piston rings are knackered by using a compression tester.but if i test it how do i no it aint the oil stems that are not buggered.when i do the compression check what number should i be looking at?any help on this would be grate because i dont want to strip my engine for nothing.cheers Rick.
 

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MEG Corporal
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All your looking for is that the number it shows is the same for each piston. Any major variation and you have a problem.
 

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MEG Captain
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but also it does not want to be on the low side either , from days of yore , yes i am old :loopy: , somewhere about the 180 psi mark rings a bell as being ok , and before anyone comes along and has a go i have had quite a few beers since then and they grey matter is turning a bit mushy :loopy: :D :D :D
 

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MEG Corporal
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Atmos pressure is 14.7psi - and the compression ratio is 10:1

After accounting for some fuel spray, just under 180 sounds about right - so the grey stuff cant be doing too bad!
 

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MEG Captain
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:woot: , and there was me expecting a putdown ;) , seriously , we are both right to a degree , they need to be even but they also need to be good pressures :L
 

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Still waiting to Wii
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when you do a compression check, disable the fuel pump, and hold the throttle wide open. The numbers shouldn't be below 150, 180 sounds pretty good, cams and other things make a difference as well as compression ratio, look for no more than 10% variance in the cylinders, and if you have a low cylinder, or all are low, take a tablspoon of light enigne oil and pour it down the spark plug hole, then redo the compression check. This will temporarily seal the rings and allow you to diagnose where your compression is going, if it goes up, rings are knackered, if it stays the same, then rings are fine, and valves are knackered, Also, leaking valve guides will not show up low compression, so if you're doing this for losing oil, and compression comes out fine, then it'll be valve guides. You can't really go by atmospheric pressure times compression ratio due to teh fact that no Naturally Aspirated engine will be 100% efficient, especially at cranking speed, and alos variations in cams, etc.
 
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