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rokon2813

Used piston - thoughts

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rokon2813

Rebuilders ;

What are your thoughts on used pistons ??

I have about 15, from 19, 23D, 243431, and 300421

Should I take them to a professional and have them measured, or are they scrap ??

Basically, are they worth anything?

While we are at it, anyone know the standard measurement for a 19 and 23D ? They look the same.

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dav

dan,

I don't know the exact measurement but I think the 19 and 23D are 3 inches.

where the value may lay is in oversize pistons. since the +.010 and + 020 are NLA, if you have good ones they may be resellable. the oversize will be stamped on the top of the piston.

as to used, I have never had to replace a piston because it was old or used. I did buy 4 with rods for a pick up only because I wanted a set to replace the bent rods when my daily driver stopped -literally and instantly- driving. but they were from a junkyard, and were therefore, used.

my old, very old even in the '70's, 1935 VLD Harley needed an overhaul, I reused the almost 40 year old pistons. (I had to use Corvair rings as '35 parts were, guess what?, NLA)(wish i'd kept that beast!)

as to the professional opinion, go for it. the local machine shop may look and say "This one is junk because..... but these are usable". and they may not charge you for looking. I was going to rebush my valve stem bushings until the shop said yeah they are sloppy but will work for quite a while longer. (one of the advantages of a low RPM motor is that they are forgiving).

your biggest problem might be properly identifying the pistons.

IMHO: the rings may be better than what a buyer currently has so I would leave them on the piston. but I would soak the piston with oven cleaner to loosen up the rings-just the way I would sell them, fwiw.

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Kent

As long as the grooves for the rings are in decent shape, used pistons with chrome rings can still give years of service. I've heard that parts for the 16 HP are fairly easy to find, due to Chinese sources, but getting them for smaller and older engines is getting more difficult. It will only get worse...

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rokon2813

I guess I will hold on to them then.

When the weather gets warmer, I'll take the pile to someone who knows what to measure and look at.

I know if I need one, I'll use them. :D

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sammiefish

yeah its hard to say but my machinist is very much about "still in spec = still good" I usually replace but hey previously used parts will change less than new... so if in spec maybe even better... if not over tired

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MrSteele

I might be wrong, but agree that a piston is one of the lesser wear parts in the engine and can be used over and over. Scoring, while unsightly, can be cleaned off carefully with a file or similar, so that it does not protrude past the ring. Even worn ring lands are repairable to an extent. Getting a piston to use if you don't have one, is a definite problem. I clean mine, put the rings back on, dip them in 10 wt non detergent oil/kerosene mixture, and store in airtight cans, such as popcorn tins or coffee cans. Then, I know I have something, forget I have it, and go looking for another when I need one!!!

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MrSteele

I left out the part of finding what I needed last time, while looking for something else, then forgetting it all over again. Something about that getting worse the last few years is what I do not understand?

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Tarheel

Don't forget that a shop can knurl pistons if they show enough wear to merit such. I don't pretend to understand Kent's angle on chrome rings, as it had always been my understanding that chrome rings have stronger "spring" and thus give a better seal in a worn bore. I had never thought of them in terms of worn pistons. That isn't to say I don't agree, Just something I know nothing about.

Anyway, knurling will take care of lost girth (or worn bore to an extent) and stop piston chatter etc. Others may see it differently.

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Kent

The stronger spring of chrome rings can help overcome wear on both the piston and the bore, as long as the bore is not out of round. You might get a bit more "piston slap" as the piston rocks in the bore, but the stronger spring of the chrome rings will help maintain compression. Knurling the piston helps reduce this slap...

Back in the day, a lot of rebuilt car engines from Sears would have knurled pistons and chrome rings to overcome tolerances that would otherwise call for boring the engine and using oversize pistons. Again, the bore cannot be out of round so much that it requires a rebore to get it in spec. Just hone it good...

Downfall is that the next rebuild WILL almost definitely require a rebore, and meanwhile you must live with the poorer sealing of chrome rings. It may always use a bit of oil, but it will have decent compression as long as the compression rings seat...

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JP

When I worked for Kawasaki, we had a local guy that would teflon coat pistons (less the ring area & pin area). This worked VERY well. We even built a lot of drag/race motors with them. I don't think there was ever a failure due to the coating.

Sadly the guy has since passed & his company with him.

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MrSteele

Kent, I have used chrome rings in cast iron bores in cars and lawnmower engines for years, but have never noticed that at time for another set of rings will require a rebore. Many times, the hone marks from the time of installation of the last set of rings is still present in the bore. About the only time the hone marks are gone, is when the owner decided to seat the rings by getting the engine to overheat on purpose. I would rather use a bit of oil than eat the bore up using cast or moly rings, both of which seat almost instantly by eating into the bore.

Just an opinion

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powerking_one
quote:Kent, I have used chrome rings in cast iron bores in cars and lawnmower engines for years, but have never noticed that at time for another set of rings will require a rebore. Many times, the hone marks from the time of installation of the last set of rings is still present in the bore. About the only time the hone marks are gone, is when the owner decided to seat the rings by getting the engine to overheat on purpose. I would rather use a bit of oil than eat the bore up using cast or moly rings, both of which seat almost instantly by eating into the bore.

Just an opinion


id="quote">
id="quote">

I think this thread/topic has just crossed over into the Twilight Zone based on this comment...??

Tom (PK)

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