Hydrolocked? Yanmar 4JH2-TE

[Geoff54]

One other thought. When the piston is protruding, tap around the sides of the piston to see if you can get the ring to slide laterally in the groove.

[Cheechako]

Originally Posted by IsaakOker

So, I've been going for a few hours now closing of any wholes so that no debris can get inside.

I've also tried getting piston 1(closest to the crank) out but I've only managed to get it 1/2inch out of the top.
I'm having a hard time finding the right angle to tap on the connecting rod without damaging anything as it likes swinging to either side.

Any tips?

STOP! Per my earlier post you need to remove the ridge in the top of the cylinder with a "ridge reamer" or you will crack a piston land! Unless there is no ridge at all.

[Geoff54]

This is tough without being there to see feel. It didn't look like there was much of a ridge in the pictures. You have cleaned out all the carbon, right? Is there enough of a ridge to catch your finger nail on?

[Geoff54]

And you are just tapping up and down, right? Not really hammering on it.

[IsaakOker]

OK, so let's see.

Is the ridge supposed to be in the liner? If yes, no there is no ridge at all, just a but of pitting from corrosion.

There are ridges all the way around the piston itself which are filled with gunk but no ring yet in sight. Only 10.5mm is out so far.

I'm tapping it - Medium strength-with a 16oz hammer onto softwood.

What is a piston land? 🤔

[Geoff54]

The land is the narrow strip of piston between the grooves. The risk is, if the ring is stopped by a ridge, if you bang on it, the ring pushing against the land may break it. Does that make sense?

[Geoff54]

Yes the ridge is in the liner where the top ring stops at TDC.

[Wotname]

Originally Posted by IsaakOker

Is the ridge supposed to be in the liner? ..... 🤔

No ridge (or lip) when new. A lip develops with use as the top ring slowly wears the cylinder wall up to the point of it's upper most travel.

[Geoff54]

Originally Posted by Wotname

No ridge (or lip) when new. A lip develops with use as the top ring slowly wears the cylinder wall up to the point of it's upper most travel.

Much better explanation than mine.

[a64pilot]

Originally Posted by Cheechako

STOP! Per my earlier post you need to remove the ridge in the top of the cylinder with a "ridge reamer" or you will crack a piston land! Unless there is no ridge at all.

Yeah, I really think the crank should come out and the pistons come out the bottom myself

[IsaakOker]

Haha great! Thank you all.

Nope, no ridge. That's confirmed.

I just took piston number 2 out in less than a minute so I'll let piston number 1 soak a while before tapping it back into clean the sleeve as well as possible again.

[Wotname]

Originally Posted by Geoff54

Much better explanation than mine.

Haha. I was working on a better one but this is a fast moving thread so the following is redundant

"A lip develops at the red circle due to wear"

[Cheechako]

Originally Posted by a64pilot

Yeah, I really think the crank should come out and the pistons come out the bottom myself

OK, no ridge so that's good.
Yeah, I think he's going to pull the crank anyway.. right OP? I guess it all depends on if the cylinder wall can clean up, if not a machine shop is likely to pull the crank anyway to reline it. However, if no ridge that's a good sign for the engine in general.
It's entirely possible you get away with only a liner or two and rings, clean things up and get it back together without full bearing job etc.

[Geoff54]

I suspect that there is a ridge but it's so slight you can't tell. As shown with the number 2 piston, you should (under normal circumstances) be able to remove the piston over a slight ridge. I bet that the ring is stuck in the groove, preventing it from retract enough to clear. Move the piston to the top, lots of penetrating oil and tap it side to side to see if you can free the ring. If not, yes, best bet is to remove the crank and pull it out the bottom.

[Geoff54]

I just looked it up and those pistons are $320 each. Go easy.