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CCKB-19.5 Compression

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I have searched all my manuals and cannot find what acceptable ranges of compression are for this engine.

I recently tested mine and it was 110 in one cylinder and 100 in the other.

What's the verdict?


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I usually figure no more than 10% difference in compression between cylinders with a minimum of 100 PSI. Doesn't much matter the engine, these figures have seemed to work for me.

Given the numbers you posted I would consider an overhaul. Not that your engine won't run OK but it is getting tired.

Just for you information........ I overhauled the Onan NHC in my skidsteer and I spent over $900 and I did all the disassembly and assembly work. Now that rebuild did include boring the cylinders and new pistons, grinding the crank and valves and seats, gaskets etc. In other words a COMPLETE overhaul. In retrospect I wish I have gone the repower route.

If you can get by with just a re-ring and cylinder hone then go for it. The expense will be minimal and you should get a few more years of service.


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Is your motor having issues? If not, with the numbers you posted for compression being in the range specified by Onan, you should be good to go. The difference from one cylinder to the other could bra result of uneven carbon buildup. Let's us know what you decide.

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I agree with Rick, if it ant broke don't fix it, and the compression readings sound good to me. I have a tractor that's been running at 100/105 pounds of compression for a couple of years now, and it runs like a top. I know an Onan mechanic very well and call him if I ever have an issue I can't figure out, he once told me if there above 90 pounds there's nothing to worry about.

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