[65t]

Deere used a CH20, (F620 ZTR) wonder if there are rings/pistons in their parts network yet, I never checked that

 

[J. Baker]

Well after about 10 hours of wrestling I finally got the engine pulled. I tore it down and found the ring end gap to be way out of specs. I have 1.6mm and the book calls for 0.77mm max. So it looks like it's just a worn engine. I still need to check my bore and pistons, but I think I have this one solved.

If the ring end gap is that wide, the bore is shot. Not maybe.
Book ring gap spec is for assembly, not for bore wear determination. There are specs for max wear in taper, out of round, and diameter. 3 separate measurements.

You should have been able to determine that the bore was shot with a compression test.

Toss that engine. Not worth trying to find parts and pay machine costs. Buy a new engine and be happy.

 

[kdammen]

That's the ring gap of my worn rings. I don't have my new ones yet. Compression was 170 psi last I checked

 

[J. Baker]

That's the ring gap of my worn rings. I don't have my new ones yet. Compression was 170 psi last I checked

And worn bore. I know what you measured, if you did it correctly.
If the engine is as wore out as you say, it couldn’t make 170.
“Ring jobs” are band aids. They don’t fix worn out engines. New round rings can’t seal egg shaped bores. Trust me, I’ve rebuilt a lot of engines. Do it right, or you’re just throwing money (and time) away.

 

[kdammen]

@J. Baker How can you determine my bore is worn by knowing the end gap of my old rings?

 

[J. Baker]

@J. Baker How can you determine my bore is worn by knowing the end gap of my old rings?

Because your ring end gap is twice what it specs at new.

How many engines have you overhauled?

I don’t use metric specs, but your 1.6mm gap is .0062”, and that isn’t just horrible, but it’s a lot. It isn’t enough to cause oil consumption unless it’s been overheated and the rings lost tension, or the oil ring is broken, or the ring land on the piston is worn. I can’t see any of your parts, but I would have done a lot more checks before tearing that engine down. A ring job is always a waste of time unless something happened to cause the rings to lose tension before wearing out. In which case I would have to make a judgement call on what to do to correct it at that point. There are different options.

But not being there, not seeing any of your parts, and you only posting one picture of the coke on the spark plug of all things, (which appears to be a stock photo and was 2 years ago) and some end gap specs that I don’t know if you properly measured….. the only logical conclusion from my seat is the engine is wore out and you should overhaul it. A ring job is not an overhaul.

 

[kdammen]

You have the decimal off 1.6mm is .062". I'll get a bore gauge and check the bore. I checked everything I could think of before tearing down the engine.

 

[Scott87]

At this point you should be dropping the cylinders off at a machine shop and have them check them b4 boring them out. Or when Baker says they are egg shaped do you know what he is talking about?

 

[kdammen]

Yes I do, and a bore gauge should show if it is egg shaped or not.

 

[Scott87]

Only if you know how to use it. I have learned by doing everything wrong at least once to bring the cylinders into the machine shop before ordering oversized pistons.

 

[J. Baker]

You have the decimal off 1.6mm is .062". I'll get a bore gauge and check the bore. I checked everything I could think of before tearing down the engine.

You are correct. I errored. If the ring end gap is .062”, then the cylinder is completely shot. It should have barely made enough compression to run, would have burned oil, and should have failed a leak down test. So, you have a lot of conflicting info.

A bore gauge is not a tool you just go borrow. They’re expensive and shops don’t loan them out.
And like Scott said, they’re only good if you know how to use one.

 

[Mike N]

.062" is large enough to drive a truck through. I'd imagine there's got to be a huge ridge on the top of that cylinder.

 

[J. Baker]

.062" is large enough to drive a truck through. I'd imagine there's got to be a huge ridge on the top of that cylinder.

HUGE ridge!!

 

[Breezmeister]

Yes I do, and a bore gauge should show if it is egg shaped or not.

Well, it's taken you more then 2 years to get to this point.....Seems you are determined to fix this engine no matter what we think......

So fwiw, the way I was taught to take the measurements. I take 6 readings, two about 1/2" to 1" from the top of the bore, then half way down, then about 1/2" to 1"from the bottom. each time, going north-south, east-west, or vertical and horizontal.

And, are you 100% sure you had the ring square to the bore ? If not, put the piston back in and use it like a level, push the ring down on to the top of the piston at the point where you want to take the end gap reading, move the piston down and take your reading.

 

[kdammen]

Thanks for the info guys, I'll have the bore checked out and go from there. I only use this machine for about 5 hours/year, so it hasn't been my top priority and it's always gotten the job done despite the engine issues.

 

[kdammen]

You guys were right. I took a bunch of bore measurements. And the worst section is at 77.12 , the wear limit is 77.063mm so twice what the max is. I'll be ordering a new engine since it doesn't make much sense to have this old engine bored out.

Surprisingly it had 170psi compression and only 10% leakdown. I'm thinking that must have been because there was so much oil in the cylinders. Check out how much oil/fuel was in the cylinder when I originally pulled the head.

Thanks everyone for your help.