Yanmar cylinders slightly oval

[IsaakOker]

What do you mean by “are the brand new rings showing new specs”?

I’ve just tried again and yes, both rings fit in the two grooves, measured the clearances and they seem to be on the lower end but within specs if I use the chromed ring as first ring and the carbon as second.

What do you think about the bevelled and straight edges of rings?
I would say that the bevelled/rounded should be number 1…

As for the taper, it’s not super apparent to the eye…

[markxengineerin]

I meant to ask, when you measure the new rings, to make sure they were falling within the spec for brand new rings. It would confirm the measurements were ok, but seems a moot point if you have the rings fitting either groove now.

Bevel, barrel, round, taper, all these words are different, so have to be careful.

The book says "barrel face" for the top ring. With cylinder wall on the right, that should look like it does here:
https://www.speednik.com/files/2019/...-52_693549.jpg
I think it's your "IT" because I can see a coating in your photo, and that one has a coating.

2nd ring is "tapered inner cut" per the book. I can't say exactly what that means, but it will have flat faces, no barrel. Hopefully you can verify by eye that TP has no barrel on it, and then be confident you've got it right.

[IsaakOker]

Aha…. Thank you very much!!

That explains a lot hahaha was just in the wording as barrel is what I was calling bevel or rounded.

Yes, so I’m case anyone else has the same issue, the chromed, barrel ring is 1T & TP is definitely taper or sharp edges 😅

Thanks a lot!!

[Don C L]

Originally Posted by markxengineerin

They should be round- there is a spec for it in the manual, I think .0008" from my memory, produced by boring + honing, which by default gives a round result when done well. Pistons on the other hand usually have complex profiles like you said.

Yeah, as soon as I wrote it I knew there is probably no way to make cylinders like that!

[IsaakOker]

So finally got all 4 pistons and their rings installed and Yanmar has actually confirmed that is the order of the rings: 1T is the first and TP is the second ring.

The question I have now is if there’s a measurement for the overlapping piston out of the block.

Not sure if I’m explaining myself but now that they’re installed when I rotate the pulley for 2 of the pistons to be at their highest point, they very slightly stick out.
By measuring very roughly with the feeler gauge next to it I’d say it’s about 0.024 or 0.6mm

I thought they were meant to be flush with the block but do they protrude 0.6mm though the head gasket opening and that’s why the head gasket has a considerable thickness?

Thanks I’m advance !

[markxengineerin]

Mine stuck out too, I was slightly concerned about it but couldn't find a spec. It's possible to check clearance if you still have the old headgasket and some plastigauge, but I didn't at the time. My engine still runs, so, must have been fine. I had removed a bit of material from both the head and block- if you haven't, you're not at risk.

[IsaakOker]

Ok, hahah

Thought it was a stupid question but yes, can’t find any guide in the manual or anything regarding protrusion of piston crowns…

I do actually still have the old gasket so could check.

I haven’t removed any material apart from lightly sanding with a 2000grit the block and head gasket surface to clean it up properly.

[IsaakOker]

Now another question,

How easy should it be to turn the engine over at the crank pulley?

I can turn it with two hands and quite a bit of effort but there’s always a point of resistance… suppose it’s the shape of the crankshaft as it's always when the two pistons are starting to rise, doesn't matter if 1&4 or 2&3.

Is this normal or should it be super easy to move as the head isn't on yet?

[markxengineerin]

With pistons in, you will feel some resistance. With the consistent location for 1/4 2/3, I think that's a good sign and probably normal. If there was one bad spot per rev, that would be harder to sell as normal.

Did you have any issues getting the rings installed on the pistons, or pistons down into the bores? I found it really difficult to remove the rings without permanently bending them, and ended up buying an expensive ring tool instead of the cheapie I usually am ok with from Autozone. Then the new pistons came with rings already installed (thanks Yanmar) so it was not needed.

[markxengineerin]

I would try spinning it over with a breaker bar on the end of the crank pulley bolt, even if you have to do a temporary install to make that happen. If you have built other engines, you may recognize this "feeling" more easily than trying to judge something with your hands, which is less familiar to most. There should be no significant force to make it spin w/ breaker bar, but ok to feel spots of small additional resistance. I remember this being the case. Oil up the cylinder walls really well if you haven't yet. Assembly lube in bearings (if you used it) is viscous so can also make things feel a bit "tighter" than you might expect.

[IsaakOker]

Yes, installing the piston rings was easy once I knew which one went where hahaha
It was more of a meticulous job because of all of the ring gapping, groove to ring measurements, etc.

I was being very meticulous as taking the rings off was a nightmare because they would break off in 1-2inch pieces. Especially the oil scraper ring as they were extremely gunked up. I nicked two three spots slightly so was afraid they would Interfere with the groove to ring clearance and then being able to spin freely but at the end everything seems smooth enough and nice so I installed them.

The current resistance when turning it isn’t really a chunky/scratchy feeling but more of a “off-orbit” feeling as the crank and rod obviously have a spot where it doesn’t have the same “direct push”. (Not sure how to explain it)

I just tried with a half inch wrench that’s maybe 12pm he’s long an it spins easily with one hand but still has that point you have to push past every time two pistons start making their way up.

[markxengineerin]

It sounds normal to me, as long as you don't feel a crunchy/scratching type feeling. Another thing you can try is loading up the cylinder wall with oil and making sure the piston/rings wipe that away nice and evenly.

[IsaakOker]

Ok, will test that tomorrow!

No scratching or feeling caught on something or so, it’s just that there’s a point of more resistance which I thought might be because of something bent or whatever but I checked and nothing is bent…

[skipperpete]

Originally Posted by IsaakOker

Ok, hahah



Thought it was a stupid question but yes, can’t find any guide in the manual or anything regarding protrusion of piston crowns…



I do actually still have the old gasket so could check.



I haven’t removed any material apart from lightly sanding with a 2000grit the block and head gasket surface to clean it up properly.

This might be of some use Isaak, it’s not until you get to the DTE and UTE engines that varying thicknesses of head gaskets are used but you need to be wary, there are 2 different types of head gasket used on 4JH2-TE so be sure to compare the new to the old. It’s not about different thicknesses .... the grommets at the ends are different [ATTACH]

[AKA-None]

You didn’t have to put the rings on more than once

You take the bare ring
Put it in the cylinder
Turn a piston upside down
Push the ring to where you want it
The measure the gap