Compression down?

Cummins12v

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So I was out riding the otherday, and i shut of my sled to help a buddy get unstuck, and when i restarted it it wouldnt rev up and wouldnt idle. I let it die, and then restarting it seemed to run fine. I only noticed on the ride home it sounded funny and had a bit of a bog around 4-5500 rpms. I did a cold compression test, and clutch side was 140psi, and the other side was 156psi. I did a compression test 200kms ago and clutch side was at 153psi cold. Anybody have any suggestions what would cause such a compression drop? Or do i need a top end... The sled is a 2006 summit x 800. Thanks
 
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RGM

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To confirm it is rings put some oil in the spark plug hole and test again, just to rule out head gasket etc. How many K?
 

d mills

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So I was out riding the otherday, and i shut of my sled to help a buddy get unstuck, and when i restarted it it wouldnt rev up and wouldnt idle. I let it die, and then restarting it seemed to run fine. I only noticed on the ride home it sounded funny and had a bit of a bog around 4-5500 rpms. I did a cold compression test, and clutch side was 140psi, and the other side was 256psi. I did a compression test 200kms ago and clutch side was at 153psi cold. Anybody have any suggestions what would cause such a compression drop? Or do i need a top end... The sled is a 2006 summit x 800. Thanks
Your mag side was 256psi? Holy fawk.
 

Cummins12v

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To confirm it is rings put some oil in the spark plug hole and test again, just to rule out head gasket etc. How many K?
Thanks, forgot about that. Sled has 7400kms, supposedly with new motor 1200kms ago. Compression cold clutch side:140psi, with oil:170psi. Mag side cold:156psi. Clutch side hot:110psi, with oil:125psi. Mag side hot:145psi. All compression tested was done at 2000ft of elevation, 8 pulls per test.
 
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