Getting another Engine ready. On 78.5 bore. Piston maybe usable? Here's pic. Can't find rings but found some nos Honda for a 78.5 piston. Will they work as long as I get end gap to speck and fit in ring grooves freely. Have hillside head for this one.

Sorry typo rings are for 78.75 piston will they work?

To ansawer your question. Ring,s a ring. As long as it set up correctly.
The only thing that would change if set up to work is the static installed tension due to it's size. I do not see that as an issue. I base this on the pressure applied during combustion. That is far greater than the static tension. Since it's an arts tapered ring make sure there the same angle thickness ect.
I say yes
My wife said they will snap

So let me know. I got money ridding on this.

Is there a manufactured difference between ART and say wiseco?
Is there a measured static tension?

Reason i ask is i have several ART 78.5 pistons but no rings with them. Disnt know i had an option for the 78.75 piston rings

Gonna get a set later this week and give it a quick hone . Then put on bottom end next week. Hopefully everything goes good. Leckich cylinder and head getting past limit gonna use this setup whilst I rebuild leckich setup.

1) The ART piston has tapered rings I believe. So no the wiseco rings will not work.
2) In my opinion adnoh's wife is right -- no they won't work. The reason I say this is because anytime you take a bigger circle and make it smaller the contact points change. It's not round anymore.
3) Make your own rings. I did have a post here at one time about it. Here it is: viewtopic.php?f=4&t=17244&hilit=rings

I figured nos 78.75 rings will work as long as ring gap is right. Only talking .25 mm larger. They are Honda nis for a 78.75 bore . It is 78.5 piston and bore now.

Find a piece of pipe. Measure it. Then cut a sliver off and cut the end. Now squeeze it smaller. Measure it at two points. It will be different at the two points measurements.
You can't do that.

When we measure ring end gap we use a feeler gauge. We are measuring in thous.
Now you wana buck off a 1/4 mm.
I don't like it.

At the end of the day you got nothing to lose here.
You got the balls to try. I give you points for that.
These are special rings (tapered) and you are not going to find any anyways. Just don't expect a miracle. It might work so prove me wrong. But that's my thinking on it.

EDIT: We are talking about .010 difference between the two ring sets. That's not a lot. So it may work. You got nothing to lose. This is gona be a great experiment and I really want to see the results. Please keep us posted on this. Hell I want to try to weld a holed piston one time but I got nothing I can use damn it.

Gonna order rings tonight. Hopefully will work it will be nice to find out.

CO, look at the difference in circumference. For 78.5 and 78.75. I would bet his bore is larger too and after a hone his piston to wall has to be larger. Not knowing the accual number it just guessing . Its worth a look I have squessed over sized pilot ring in a bore just playing around they will have to be re-gapped. I would guess around .040" diff
I day back yard hacker those puppies. All your out is some time and little money. I know you would, it's ok to say it man. It our nature

I will buy the rings from you if you don't want them

Whats the actual measurements on piston wall clearances? Just curious as i think they would work too with the .010 clearance

Using quick dirty method can barely get .004 " feeler gauge in between piston and cylinder wall. After very light hone maybe lil more but not much. Should be within spec for 78.5 piston.

Rings came today fit piston nicely. Here's pic of ring in cylinder. Think they will be fine as long as file down for ring gap.

Pic of part numbers

I'm with Can Odd on this one. It may work initially but for how long is the question!

I'm guessing you are going to see a ring snap because you are compressing it. Even with opening up the ring gap the ring was designed for a larger bore and will be ever so slightly oval shaped because it's being compressed.

Rand

May I ask where you found these rings

Here are two sets I found on feebay: https://www.ebay.com/itm/1985-HONDA-ODY ... qo&vxp=mtr
Based on my info they are post recall 79mm rings.
I would buy both sets as you can always sell them.
Yes I know you are looking for 78mm but maybe someone will have a 79mm piston for you.
Unfortunately you would have to do a bore job.

Edit: here are some 78.75mm rings: https://www.ebay.com/itm/Honda-FL350R-O ... bi&vxp=mtr

Those are the same as I have they are for 78.75 bore. Im thinking they will work only .010" bigger. After putting on piston and seeing them in cylinder think gonna be good. Got bearings for bottom end now gaskets and seals then start assembly.

Ok never posted results of this. Engine running for months no issues. Set ring gap right seems to be fine. Maybe an option if original piston and bore is ok.