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Hi New to the forum but looking for some insight.
I have a 2015 Ranger 570 Midsize. I have checked compression and had none so i installed new piston rings and cylinder. Now i have 30psi (This does have a auto decompressor). I have adjusted the valves intake .06 and exhaust .08 . i have changed fuel and checked injector. new spark plug. checked for the flywheel key being sheered. its not. Looking to see if anyone has had this problem or knows a solution?
 

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According to my Service Manual you should have 80 to 120 PSI with the Compression Release. You've got something wrong somewhere. You didn't mention the reason for the replacing the rings and cylinder so we don't know what else to consider. Did you check the valves and valve springs while you had the head off? Leaking valves will cause low compression and they can leak either becasue they are burned, bent, valve guides are severely worn or springs are broken. A worn cam will not lift the valves far enough to allow intake air to enter the cylinder with the result of low compression. If cam timing is wrong compression won't be correct. Something could be wrong with your compression release. Did you check it for binding or wear? A warped cylinder head will leak at the head gasket. Did you torque the cylinder and head?

A cylinder leak down test can be helpful in locating reasons for lost compression.
 
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I agree with pyro in that it'd be helpful to know what caused the loss of compression in the first place. I've posted on here about dust inhalation through the crankcase breather tube. I've rebuilt about six 570 top ends due to this reason. Of the six, five needed a valve job as well as piston/rings/cylinder. X2 on the leak down test.
 
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