Just brought home a 1912 - Page 6

J-Mech · #51 05-30-2018, 11:25 AM

Quote:

Originally Posted by sorner

Both sides? Same issue?

You've never seen and engine that had stuck piston rings? How about broken ones?
Yes, it could be both. Maybe it got hot and they lost tension.... or broke.

sorner · #52 05-30-2018, 11:36 AM

I have, but that was due to rust in the bore. I'm just skeptical that rings became stuck or broken in both sides... But I'm also skeptical of the low compression, when I can see the bore and the piston, and visually the bore looks nice and not all worn out, and there's no scoring at all. All signs point to some issue with the rings, whether stuck, broken, or worn... At this point the only way to know for sure is to pull the pistons out and looking at the rings.

Oak · #53 05-30-2018, 10:43 PM

Most people think it's a waste of time but why not do a leak down test? How did the valves and seats look?

J-Mech · #54 05-30-2018, 10:51 PM

Quote:

Originally Posted by Oak

Most people think it's a waste of time but why not do a leak down test? How did the valves and seats look?

Putting air pressure in the cylinder like he did was a leak down test. Just without the fancy gauge.
If he only heard air through the crank vent, valves are at least trying to hold.

Oak · #55 05-31-2018, 08:04 AM

Quote:

Originally Posted by J-Mech

Putting air pressure in the cylinder like he did was a leak down test. Just without the fancy gauge.
If he only heard air through the crank vent, valves are at least trying to hold.

Oops, I missed that Jon. I went back and re-read everything...now I'm on the same page.

Keep swinging at it Steve.

sorner · #56 06-05-2018, 10:55 AM

I've got the new rings, and new gaskets, and I'm taking the Onan apart and fixing it right.

In other news, I decided to drop in my re-sealed Kohler Magnum M18 engine to see if it would fit, and it bolts right in, and the driveshaft mates up perfectly. So, that engine for a re-power option is definitely a possibility if something goes wrong with the Onan project, but I really want to keep the 1912 original with the Onan engine.

J-Mech · #57 06-05-2018, 11:02 AM

If you haven't taken it apart, how do you kow it needs new rings?
How do you know what size rings it needs?
If you don't plan on boring it, you are not "fixing it right", you're just band-aiding it. Just doesn't seem to matter how many times it gets said on here, it's never enough. "Ring jobs" are only temporary.

Also interested to know why Onan and Kohler tractors Show a different part number shaft if they are the same..... I would have bet several dollars the shaft wouldn't fit.

sorner · #58 06-05-2018, 11:17 AM

It is taken apart already. Everything in the bore measures fine. The new standard sized ring gap measures about .12, spec range in the manual is .10-.20. Maybe rings won't fix it (I hope they will), but you're the one who suggested the rings were the low compression issue, cracked or lost tension. They weren't cracked or broken, so I have to go with they lost tension somehow. The bore is not scored or visibly worn. I have seen worn bores with a ridge at the top and the bottom and everywhere in between is smooth as glass, this has no ridge and still has visible crosshatch in both sides. I've never once claimed to be an expert at this, but I'm not an idiot. It's not like I'm just trying to re-ring an engine that has a severely worn bore.

If everything checks out and it's just bad rings for whatever reason, why does it need bored? I do not understand that statement.

J-Mech · #59 06-05-2018, 11:31 AM

Quote:

Originally Posted by sorner

It is taken apart already. Everything in the bore measures fine. The new standard sized ring gap measures about .12, spec range in the manual is .10-.20. Maybe rings won't fix it (I hope they will), but you're the one who suggested the rings were the low compression issue, cracked or lost tension. They weren't cracked or broken, so I have to go with they lost tension somehow. The bore is not scored or visibly worn. I have seen worn bores with a ridge at the top and the bottom and everywhere in between is smooth as glass, this has no ridge and still has visible crosshatch in both sides. I've never once claimed to be an expert at this, but I'm not an idiot. It's not like I'm just trying to re-ring an engine that has a severely worn bore.

If everything checks out and it's just bad rings for whatever reason, why does it need bored? I do not understand that statement.

It's not often that a bore is good and rings will fix it. If the end gap is good, the bore is good, and none of the rings are broken.... then maybe it isn't a cylinder issue. It is possible the rings have gotten hot and lost tension.... but that usually results in a scored piston, blue sections on the bore or piston erosion and a burnt valve. There should be an obvious issue. Perhaps someone already took it apart and honed and rerung it and that is the issue. I can't see this engine, and you haven't posted any pics..... nor can I measure the parts. Relying on you here.

DeltaCub · #60 06-05-2018, 11:55 AM

Quote:

Originally Posted by sorner

It is taken apart already. Everything in the bore measures fine. The new standard sized ring gap measures about .12, spec range in the manual is .10-.20. Maybe rings won't fix it (I hope they will), but you're the one who suggested the rings were the low compression issue, cracked or lost tension. They weren't cracked or broken, so I have to go with they lost tension somehow. The bore is not scored or visibly worn. I have seen worn bores with a ridge at the top and the bottom and everywhere in between is smooth as glass, this has no ridge and still has visible crosshatch in both sides. I've never once claimed to be an expert at this, but I'm not an idiot. It's not like I'm just trying to re-ring an engine that has a severely worn bore.

If everything checks out and it's just bad rings for whatever reason, why does it need bored? I do not understand that statement.

Not boring a cylinder block for a rebuild is like building a foundation for your home without the proper footings! You can build the wall but it is not right and it will result in costly problems til the initial problem is addressed.
Now about your engine, the bore may be sort of round, but it is not correct. Cylinders need to be trued, they need to have the glaze removed and proper crosshatching for the rings to "seat". It may have some crosshatch and no ridge but it needs boring if you are going to rebuild it properly.

Rebuilding engines can be costly. But it is cheaper in the long run to spend the money up front so you won't have the same problems and additional expenses later.