Stihl MS 192tc misbehaving. Runs, no power. Suspect lean out.

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cdherman

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OK, I bought this 192tc new about 10 years ago, as I tend to one hand a saw for trimming work and when I am up in my poor mans bucket (a well secured shuttle cage on my reversed pallet forks on my loader tractor) I used to climb a little, but I am just too heavy anymore and approaching 60.

I run exclusive ethanol free gas and stihl synthetic oil. 50:1 Gas also gets a dose of Stabil before use. I just get 5 gal of ethanol free every month or two, treat it, and use that in ALL my small engines.

So many people gripe that the 192 is gutless etc. But I love it. For what it does, which is small limbs in awkward places. And I can take a long small limb on the ground and chop it into 16" kindling, standing with the left arm holding the limb and the right running the saw.

Anyhow, please no negativity to the 192. Sharp and used right, its a beast.

But....

Lately, it starts as always, revs fine, idles fine. Then bogs nasty bad when under a load. And eventually even dies. So couple of ideas. Some videos suggest that the vacuum relief valve from the gas tank could be plugged. Does the 192tc have that? Runs the same from the get go, so I am doubtful the vacuum building up is the issue. But worth it to check I suppose.

Another thread suggests the carb needs rebuilt and a video shows a hardened diaphragm causing issues. I can tear it apart and see. I am meticulous about gas, but 10 years in 10 years......

Finally another thread suggests the intake boot can fail. That could be the culprit too. Last year I ran the saw over (never sit your saw on your tractor tire), but just dealt it a glancing blow and a new $30 handle housing fixed things. BUT, I had to pull that intake boot out to install the new parts.

Anyhow, looking for wisdom. I really don't think the saw is shot, meaning scored piston. Has the same old compression as always.

Thanks in advance.....
 

Sierra_rider

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I used to have a 192t, which was having similar issues...it would start, but didn't like to have a load on it and would stall out if you throttled it up quickly. At first it would only occasionally have these issues, then finally it was all the time. I suspected an air leak, so I tore it down and found a torn intake boot.

New boot, same issues...ended up replacing the impulse and fuel line, as it's just a good thing to do on a 10+year old saw with running issues...anyway, final issue ended up being crank seals.

If you do go the route of replacing crank seals, there are 2 different variations available for the 192. One is if you intend to split the clamshell, the other is if you don't. I split mine as I ended up wanting to freshen up the top end anyway.
 

Woodslasher

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+1 for what Dean-O said. I've seen those exact same symptoms on a Stihl trimmer, started fine, idled fine, but it would die when you touched the throttle. Now if it even begins to sound funny I'll clean the spark screen. To clean them I'll just grab 'em with a set of pliers and use a Mapp torch to get it glowing red. Once it's good and red I turn off the torch and hit it with a wire brush as soon as it isn't glowing red. Do that until the screen looks clean when you hold a light behind it.
 

cscltd

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Not hatingn192s, but the crank bearings can wear faster than normal- with chain off, see if crank moves back and forth (not in or out) they suck in air from that area via seals
 

mbrick

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Check the carb and see if it has the accelerator pump version.

Sierra is correct about the bakelite and standard rubber crank seals.

New fuel and impulse line is always good.
 
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+1 for what Dean-O said. I've seen those exact same symptoms on a Stihl trimmer, started fine, idled fine, but it would die when you touched the throttle. Now if it even begins to sound funny I'll clean the spark screen. To clean them I'll just grab 'em with a set of pliers and use a Mapp torch to get it glowing red. Once it's good and red I turn off the torch and hit it with a wire brush as soon as it isn't glowing red. Do that until the screen looks clean when you hold a light behind it.
This is goofy. Pull the screen out, and toss it? All this science to clean a screen that serves no purpose, unless you are in a wild fire, seems pointless. Spark arrester screens never clog, unless the oil mix is poor quality. Either way, they are summarily and routinely discarded.
 

cdherman

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Well, thanks again for the very competent replies. I would be really sad if the crank seals are shot.

I have 2 John Deere CS-56 saws. They were made by an italian firm, EFCO. One over 20 years, the other around that. I've had to replace soft parts (lines mostly) but both saws just keep howling. Both were abused by my father/brother who cannot seem to learn about ethanol. And both are heavy and sadly, few parts are available. So I figure I'll be down to one and then none as bits and pieces fail. But in spite of a lot of hours, no real major system failure.

My 192TC has never seen professional use. If the crank seals just gave up after 10 years, even though it was well cared for, then I will downgrade Stihl mightily in my terms of endearance. No way I should be splitting the case. I'll try the easier stuff first.
 

Dean-O

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This is goofy. Pull the screen out, and toss it? All this science to clean a screen that serves no purpose, unless you are in a wild fire, seems pointless. Spark arrester screens never clog, unless the oil mix is poor quality. Either way, they are summarily and routinely discarded.
In California if you are out logging and a wildfire starts one of the first things investigators do is check all the chainsaws and any of them are missing the spark arrestor then that operator is in big trouble.

You say spark arrestors never clog? On bigger more powerful chainsaws they rarely ever do. But on smaller saws and other equipment they clog all the time. The units that come in the most with clogged screens are 192’s, 170’s, 171’s. Trimmers are FS 38’s FS 56’s and even FS 240’s. Blowers are BG 50’s 56’s 86’s. It’s not just a Stihl thing because Echo SRM-225’s come in with clogged screens all the time. Some Husqvarna products like the 326L and the smaller chainsaws occasionally have a clogged screen.

It’s not just the bad oil mixture. It’s not running the unit at full throttle. A lot of the trimmers the customers use to edge their lawns and run the unit for long periods of time at 1/4 throttle. Same with the blowers and small chainsaws that they use for tiny limbs and never use the unit at full throttle. The engine never gets hot enough to to blow that tiny amount of carbon though the screen or run hot enough to burn the deposits off the screen like a large chainsaw running at full throttle cutting trees can do. After running the unit at 1/4 or 1/2 throttle for years and years eventually the screen becomes plugged.

I have personally removed and burnt carbon off spark arrestors at least 1000 times over the years at my shop. I ask the customer how do they use the unit? When they tell me they edge the lawn with it I tell them to go ahead and do the edging but before you shut machine off go out and weedeat at full throttle for 5 mins to get that unit heated up to get that carbon blown through the screen.

So yes a bad oil mixture can cause a clogged spark screen for sure, but that’s not the only reason.
 
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