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Discussion Starter #1
My first time here, hope this is the right place.

I have a Tecumseh HH60 on a Troy Bilt Horse tiller. After setting for a number of years I went through the usual and got it running, only to find that after 10 minutes or so it was belching smoke. Suspected something internal, tore it down, only thing that look amiss was a very polished cylinder. Ordered new rings and head gasket, honed, reassembled, got it running very well. After not so many minutes it was belching smoke as before. Jump to the finish, it is pumping oil through the breather into the carb, most likely the only problem in the first place.

Breather is clean, valve in the breather seems to be working, but there seems to be enough blowby that it is blowing oil into the valve spring area, not returning fast enough, after 10 minutes or oil fills the valve area enough that it begins blowing spit into the air cleaner through the breather tube. If you leave the tube off, it spits some oil, but the motor runs great and doesn't smoke at all.

I would suspect I installed the rings wrong, except the symptoms are the same as before. Regardless, I installed them with the markings on them pointed up, the one marked 1 first, the one marked 2 in the middle. Correct or not? The oil ring was different than any I've seen, it is 2 very thin rings, the spring didn't go behind them, rather between them, standing up instead of under them, and keeps them apart. Since it doesn't seem to be burning oil in the normal sense, I would think they are ok.

This thing ran fine, burned no oil before storing for 4-5 years. It seems the same before and after the ring job. I have no idea how much air should be coming out the breather, but it's a steady puffing, not like an air hose running, but a slight bit with puffing, obviously in tune with the piston. With the breather off, open to the valve cavity, there is the steady air coming up, with oil that appears to be splashing up, I would think from the splash lubrication.

Any thoughts? Any idea if my rings are installed correctly? Is it normal for that much oil to splatter up into the valve area?
 

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There are two primary causes for your symptom.
1. Oil, either overfilled or wrong viscosity. Since this is a Horse tiller, the engine sits at an angle. Ensure you check the oil level with the engine level. This would be my guess.
2. Wear, resulting blow-by. Without doing a leak-down test, all I can tell you is that before you honed the cylinder, if there was no cross-hatch remaining it was worn.

If the spark plug is coming out oily, you probably have blow-by, or it's overheating. Some might cite ignition timing, but I've never seen a Tec. overheat from a worn breaker-point rubbing block (resulting in retarded ignition).

There are other reasons, such as a crankcase leak (resulting in breather unable to maintain partial CC vacuum), worn valve guides, worn breather, even over-speeding. When you had it apart, you had a lot of evidence at hand. The wear pattern on the piston skirt would tell you a lot, more than 20% wear is a indicator of advanced wear. A cylinder with a visible depression near the top is very worn - occurs at the top of ring travel.

About the ring installation, hard to say...did you get OEM rings? Ring-end gap would give tell you a lot also, but you'd have to tear it down again.
 

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Discussion Starter #3
When I first brought it out of retirement, I changed the oil, I did overfill it about half an inch. Once I put new rings in, it was exactly correct, made real sure. 30 wt. Rotella.
Now, I did check it without screwing the dip stick down, just put it down until the threads hit. Guess I need to find the manual and make sure that is not an issue.

Spark plug isn't oily, wasn't run long enough to overheat.

The cylinder was almost polished, which is why I went the new ring/hone route. There was no noticeable wear on the piston, the cylinder at the top only had a very slight wear on the sides. It honed out with little effort. The motor really had very little use. I suspect blowby is causing this, but not sure what to do about it. I guess tear it down, take pictures and see if anyone can give hints from what they see. I'm kind of disgusted with it right now.

for what it's worth, before it sat it ran just fine. When I pulled it back out I cleaned the fuel system and changed the oil. As I said, I did overfill it. Not realizing at the time the smoke was coming from oil out of the breather, I assumed bad ring problem from sitting - rust or whatever. But, even if that was from overfilling it, I would think on reassembly and the right amount of oil that problem would have gone away.
 

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Discussion Starter #4
I found the manual, dipstick screws in to check the oil. Checked, it's exactly on the full line with the tiller sitting flat as the manual suggests. Oil level is not it.

Ran it, about 10 minutes I it is spitting oil out the breather tube. There is enough airflow out the tube I'm sure it is not correct. I strongly believe I have a ring problem. The rings I used came from Orielly Auto Parts, I didn't find any on line, found lots of "no longer available".

I'll tear it down again. I have a friend who has rebuilt many- maybe thousands - of motors, many small ones like this. I'll take it by Monday and see what he thinks. Maybe he has a source of better rings, who knows. That is about all that is left.
 

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That strange oil ring may be the issue. FYI there are specs. on CC vacuum, typically 2-4 water column inches at idle and go up from there. You can build your own manometer quite easily, and we still use one today. I've attached a photo from a Kohler K181 service manual. We bought the digital one, it died in a year so we're using old school one again.
Even back-pressure can create the symptom, I listed the primary causes, not all of 'em.
 

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