024 Stuck Ring?

[nedsim]

Several months ago I'd been using my Stihl 024 for a few hours. I shut it off for perhaps 1/2 hour while hauling brush. When I went to restart it -- nothing. I set it aside and used another saw for the rest of the day. I got back to it a few days later, and still no sign of life, and it seemed to pull over awfully easily. I don't have a small engine compression tester, but used what I had by comparing readings to an 026. The 024 was less than half the 026. Set it aside again and when I came back to it a week or two later, it started right up, and though I didn't try cutting with it, it seemed to run fine. Next time I tried it wouldn't start. Decided today it would be a good cold weather project, so brought it into the shop and tried again -- started with a couple pulls, sounds OK, idles, though I still haven't tried putting a load on it.

Peeking into the exhaust port, the piston and cylinder look pristine. I bought the saw new around 1987 and it's never been abused, except perhaps a little fuel neglect. It's been fed only canned fuel, 100LL, or ethanol free fuel for the last 5 or 10 years.

My questions:
-Is it unusual/possible to have an intermittently stuck ring?
-What are the typical causes?
-Is there anything else that I should be looking for before tearing it down?
-Any reason not to test it under load if it'll run tomorrow?
-I'm not a fan of elixirs like Seafoam, etc., but, if it is a stuck ring, is there anything worth trying before I start tearing into it?

 

[Mad Professor]

Post a picture of the piston/rings through the ex port.

If it is reading 1/2 the compression of a running 026 something is up.

 

[Chevboy0167]

No idea if all this stuff works but......

https://xado.us/collections/automob...roducts/anticarbon-anti-carbon-engine-cleaner

https://www.liqui-moly.com/en/us/valve-clean-p000041.html#2001

http://www.motorvacsalesandservice.com/MV4.html

The idea here is to remove sparkplug, bring piston up to top dead center and drop some cleaner through plug hole and let it set for a few days or even a week. Dump out or flush out, then repeat the process a few times.

Or cheaper yet, try a mixture of ATF, (automatic transmission fluid), mixed with diesel fuel to the same method as above. Plus, you could add a bit of ATF in your mixed fuel and 2 stroke oil. Run it hard and hot for a few tanks.

Kind of just spit balling here...... results may very!

 

[nedsim]

Post a picture of the piston/rings through the ex port.

If it is reading 1/2 the compression of a running 026 something is up.

I'll get pics later. But as I said, the piston looks perfect - no scratches or shiny, worn patches - just the original machining marks around the circumference. I tried pushing on the rings with a probe to see if either would move at all, but couldn't tell much.

 

[nedsim]

No idea if all this stuff works but......

https://xado.us/collections/automob...roducts/anticarbon-anti-carbon-engine-cleaner

https://www.liqui-moly.com/en/us/valve-clean-p000041.html#2001

http://www.motorvacsalesandservice.com/MV4.html

The idea here is to remove sparkplug, bring piston up to top dead center and drop some cleaner through plug hole and let it set for a few days or even a week. Dump out or flush out, then repeat the process a few times.

Or cheaper yet, try a mixture of ATF, (automatic transmission fluid), mixed with diesel fuel to the same method as above. Plus, you could add a bit of ATF in your mixed fuel and 2 stroke oil. Run it hard and hot for a few tanks.

Kind of just spit balling here...... results may very!

If it'll start today, I'll try some ATF in the cylinder and cut some junk wood for tonight's solstice bonfire.

I'm not necessarily looking for a quick fix, though quick is good. The saw is all original except for external maintenance stuff, so I'd replace the fuel lines, seals, etc. while it's apart.

 

[Chevboy0167]

Proper checks would be a vacuum and pressure test first before you would tear it apart at all. Rule out any leaks in the crank seals, gaskets or intake manifold. If those test pass, then you could remove top end for a look see and measure ring wear and end gap in the cylinder.

My suggestions are non-intrusive if all else test good.

I have to torn down equipment for stuck rings and carbon clogging. Time consuming and just a PIA when that is it. It also helps to run a good FD rated oil mixed with your fuel with properly tuned carb settings.

 

[nedsim]

Proper checks would be a vacuum and pressure test first before you would tear it apart at all. Rule out any leaks in the crank seals, gaskets or intake manifold. If those test pass, then you could remove top end for a look see and measure ring wear and end gap in the cylinder.

My suggestions are non-intrusive if all else test good.

I have to torn down equipment for stuck rings and carbon clogging. Time consuming and just a PIA when that is it. It also helps to run a good FD rated oil mixed with your fuel with properly tuned carb settings.

Thanks, we're more or less on the same page. I'm not looking for trouble or a project, but don't want to ignore a problem that may cause damage. I ran the saw for a short time yesterday and it didn't bog under load easier than I'd expect for a small saw. While it was warm I squirted a little Mystery Oil in the cylinder and let it sit overnight.

I'll do a pressure and vac test and get my hands on a proper compression tester to get real numbers on the compression. If both check out and it continues to run I'll leave well enough alone.

I'll post some pics in response to MP suggestion.

 

[nedsim]

Post a picture of the piston/rings through the ex port.

If it is reading 1/2 the compression of a running 026 something is up.

A couple pics. There may be some excess wet oil that was blown out after an overnight dose of Mystery Oil in the cylinder, per Chevyboy's suggestion.

 

[Mad Professor]

A couple pics. There may be some excess wet oil that was blown out after an overnight dose of Mystery Oil in the cylinder, per Chevyboy's suggestion.

The saw was ran too rich. Either carb, or mistake in mix oil.

It looks like MM oil took the carbon/burnt oil off the piston which looks good now.

Note how oily/carbony the ex port is. Put some fresh mix in and make sure carb is adjusted.

 

[nedsim]

The saw was ran too rich. Either carb, or mistake in mix oil.

It looks like MM oil took the carbon/burnt oil off the piston which looks good now.

Note how oily/carbony the ex port is. Put some fresh mix in and make sure carb is adjusted.

I'm careful of the mix, so that's unlikely. I am conservative in tuning (tending to the rich side) so an over-rich condition is very possible. On the other hand, the pics look worse than the actual saw as a result of the MMO treatment, and when I check my tune against a tach I'm generally not too far off. But something made the ring stick so...

For now I'm gonna go with a vac/pressure test and a real compression test and run it.

 

[president]

A couple pics. There may be some excess wet oil that was blown out after an overnight dose of Mystery Oil in the cylinder, per Chevyboy's suggestion.

your plug end looks like there,s no gap?

 

[nedsim]

your plug end looks like there,s no gap?

Bad lighting -- the gap is in spec.