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5,610 Posts
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Hypothetical question...if I were to swap a used set of cylinder jugs and matching pistons on to my existing engine, what work, if any, would need to be done to them before installing. Assuming that before this donor bike was tore down the compression was good on both cylinders, could you just drop the cylinders and pistons in, or is it recommended to at least hone and get new rings?

This is for a '78 CB400T engine, are new rings still around for these? Expensive?

Thanks
 

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It's probably not a bad idea to hone & new rings, but, as long as you keep the parts matched it should be just fine.
I have done this before myself with good results.
 

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Sensei
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27,164 Posts
Quick Hone...YES.... Rings needed?...Determined by end gap after honing...
 

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Sensei
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27,164 Posts
You put the rings (one at a time) into the bottom of the cylinder, then using the piston to "square it up" and push it in ( about 3/4 way up) or at least over an inch... Measure the end gap with a feeler gauge..... Specs are generally anywhere from about .004" to .012" for the compression rings for your bike... At .020" they need replaced...Oil scraper rings are usually about double the comp ring specs (allowed to be "looser".....Yours should be .008 to .035".....replace at .043"
 
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