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Discussion Starter · #1 ·
I have pulled my crankcase apart on my 1978 CB 400 T II mainly just to check things out and get it cleaned up. It has been sitting for about 8 years. It ran pretty good at that time, had some overheating issues. Odometer says about 10,000 miles on the bike which I believe to be true. There is a bit of carbon build up on the top of the pistons but everything else looks in pretty good shape. My question is whether I should replace my rings. I am going to remove them and clean them up, and i will measure them to make sure they are still in tolerance and replace them if they aren't. But if they are in tolerance (I am assuming they are due to the low miles and low visual wear) should I replace them anyway since I am in there? Also, if I don't replace the rings should I still hone the cylinders or do I assume they will still be well seated?
 

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I am by no means that knowledgeable about the 400 series, but if you're into an otherwise good-running engine I think it behooves you to put new rings in it. It certainly can't hurt, since if for no other reason, rings that are compressed a long time and inactive as well, like yours, could lose some of their tension and not seal as well as a new set would after a hone and quick break-in. If you weren't going into the top end that would be one thing but since you're there, I'd do it
 

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At the absolutely very least, hone the cylinders. Conventional wisdom is that if you don't, you'll never get a decent seal with the rings.
 

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Discussion Starter · #4 ·
Yikes! $30 each for ring sets. Is that a good price?
 

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If the rings are not out of spec, why replace them? I have reused rings several times when doing gasket replacements on heads/cylinders. Just lightly hone the cylinders, and put it back together.
TOOLS
 

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It's always been my opinion that if you distort those rings by peeling them off that piston chances are they won't seal the same way they did before. If I take them off the pistons they get tossed. It makes no sense to do the job twice and gasket sets cost money.
 

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It's always been my opinion that if you distort those rings by peeling them off that piston chances are they won't seal the same way they did before. If I take them off the pistons they get tossed. It makes no sense to do the job twice and gasket sets cost money.
Piston rings are by design made from very hard metal. Hard stuff doesn't distort- it breaks. If the rings were malleable enough to distort, they wouldn't do their job. For that matter, they get spread open and possibly even twisted in the process of installing them- if that caused issues, they'd never work in the first place. My understanding of how stuff works, anyway.
 

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Opinions vary a lot on this subject. Personally I toss the rings any time they come off the pistons and most of the time with just removing the pistons from their bores. Yeah, $30 a pop for rings isn't cheap but I'd rather eliminate a potential problem instead of having to do the job a second time. Beware of the cheap rings on eBay, they're cheap for a reason.
 

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I second the Jim's advice of only using quality rings. I tried the 'cheap' route on ebay, and ended up buying another set of quality rings PLUS another gasket set. Cheap isn't always cheap !
 

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Discussion Starter · #10 ·
Good to know, I was looking at those and wondering.
 
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