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Do I need to replace my piston rings?

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#1 DannyG


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Posted 02 April 2015 - 06:58 PM

I have a 1960 Dnepr K750 that has low compression on the left cylinder. I disassembled the left side hoping to find a smoking gun and found nothing visable. I purchased a new set of gaskets and bolts from a dealer in the Ukraine for reassembly. The internals look great, no burn marks no scaling no signs of anything wrong. I took the piston with the ring on it and slid it into the cylinder and I was able to compress the rings by hand with very little effort to get the piston to slide back in. I'm thinking it should have been harder to compress and should have required a ring compression tool. Because the were so easy to compress should I replace them? What is the procedure for sizing a new set of rings too?

Thank you

#2 racepres


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Posted 02 April 2015 - 08:31 PM

Take the ring off...does it stay oversized?
Give it a Slight twist holding just the ends...does it stay twisted?
If No to Both...Ring has Not lost it's tension, and is good...Put it back and do a Crosshatch on the Cylinders and go.

#3 lobofuego


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Posted 03 April 2015 - 06:34 AM

As above! and when sizing a ring  after checking bore etc, Get the ring you are going to use( I usually buy an oversize ring) fit into bore using piston to keep it square, and in Midbore check the gap between the ends...
It should be 3 thou,per inch of bore size....if it needs a bit more gap, delicately!...file till it fits,
space ring gaps when fitting.....have fun!

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