M-18 running rough/missing

[J-Mech]

Originally Posted by john hall

I thought about that---afterwards. I measured one of the pistons against an old one and it seemed pretty close. Not a huge deal to pull back apart, other than cleaning up the silicone. I can honestly never say I've had to file the gap on a set of rings. Most of the time I've always used OEM packaged rings other than a couple times using "name brand" aftermarket (such as Perfect Circle). Guess at this point there is nothing to do other than pull one side down and check them.

How about the oil expander ring, shouldn't have to file that one, right?

I've only ever had to file rings on a Kohler. Always check them, and usually have to file them (Kohler).

If the oil ring is 3 piece (should be) you have to check the thin rings. The "accordion" ring you don't. The oil rings are usually ok, but I've had one that was tight. Actually, I remember that motor and the skirt clearance was at the tight end of the spec. Went together fine and it still running... but it was tighter than I usually get from that machine shop. I like them to be at the tight end... run longer that way. But you have to be careful. Too tight, and they can seize if overheated or run lean.

Yeah... take it back apart and check the gap. Bet you find there is no gap.

[john hall]

OK, I'll pull one side down and see what we find. I'll try a file and honing stone, figure a Dremel will be too aggressive and uncontrolled. Kind of weird how the rings were shipped, separate from the pistons. The diagram for the rings was too vague--seems top and middle showed the same sequence of possibilities. Between the service manual and the old pistons is how I confirmed ring location. I think it was internal taper up on middle, square edge ring on top---going by memory, don't quote me on that one. Regardless, that shouldn't make it tight--unless the piston grooves are different diameters. For giggles, I can check that too. I'll post back what I find--may be a couple days.

[john hall]

WHAT ring gap? Maybe .002"--and that's a BIG maybe. Starting to think they sent the wrong rings! Anyway, I only had time to pull one side down and check the top ring. Maybe tomorrow I will have time to try my hand at widening the gap. At least the problem is found. I'll double check the piston itself while I'm back in there.

Got a question for anyone that has rebuilt one of these. Looks like my gasket set (aftermarket) came with a couple jug-to-block gaskets. My service manual is a reprint of probably the original, it calls for silicone here. Did Kohler ever switch to a gasket instead of silicone? I used silicone and it appeared to have worked fine.

[Sam Mac]

Now you have an excuse for buying a new tool.
JEGS Piston Ring Filer: JEGS 80514: JEGS Performance Products Piston Ring Filer.

[Alvy]

That reminds me of a 351 a friend and I put together years ago. He bought file fit rings and we bought one of those tools. Trying to figure out how much pressure to apply while filing. Well all I have to say is take your time because when we got impatient about how long it took to do one we spun it a little too fast with too much pressure and then, yeah, gap too big. Right in the garbage and no extras.

I think you said you're a machinist so you should have plenty of patience.

[john hall]

You know the saying ignorance is bliss, well now that I have been "educated" (looked up the tool Sam suggested and that lead to YouTube, you get the idea) so much for needle files and a honing stone. Debating making one of those ring filers---looks like a Dremel cut off wheel should work--HAND CRANKED, of course. And here I was trying to come up with a slick way to grind the valve stems without having to send it back to the engine shop (actually got a plan for that).

Looking at other postings today (Zippy), I know 2 guys that would not vote for the 18XX machines as their favorite.

At least the 2072 and the 982 came effortlessly out of hibernation today so dad could mow chickweed and onions.

Well, got 3 options: buy, make, or borrow one of those tools.

[J-Mech]

I'd use the gaskets. I thought they all had gaskets, but I don't remember.

Just put the ring in a vise and use a hand file. It doesn’t take much.

[john hall]

I'm thinking I saw a pic online of a set of Kohler gaskets online that may have included jug gaskets, that's why I was asking, it got me curious. Maybe there was a service bulletin to no longer use silicone? As long as the gaskets aren't extremely thick I can't see where it would hurt. As far as I can tell, the engine was still together with the original silicone with no signs of oil leaks (there may have been a sweat but who cares on something that has been together for 30 years).

I'll try one of the rings with just a file and see how big of a pain it is. There was some interesting notes about chamfer and deburred edges being too large on a video put out by Mahle (I think). If nothing else I learned a lesson--check the rings! Seen dad spot check them before just to make sure nothing looked crazy, but never encountered a set that was too tight.

[john hall]

Pulled the engine back down and yep NO RING GAP. Had a friend to suggest clamping a file in a vise so I would have good control over the filing. Worked well, was able to keep things nice and straight. Filed all the rings including the small oil rings to where a .011" feeler gauge would go--used a .015 for a high limit--2 of the oil rings were snug on that. Got one oil ring a bit tapered, but not so much it would exceed the book value of .030" gap--minimum was .010". Anyway the worst part was getting all the silicone back off. We only managed to tear it apart, file rings, and reassemble today, but at lest we made progress. It took a lot less force to tap the pistons in, really could push by hand with a firm grip. Engine turns over like it should. Now on to grinding the valve stems to set the clearance.

[zippy1]

Originally Posted by john hall

Looking at other postings today (Zippy), I know 2 guys that would not vote for the 18XX machines as their favorite.

Actually John, after the replacement engine, the 1872 is my favorite tractor