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.....
 
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.
 
+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.
 
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
 
+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.
 
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.
 
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.
 
Hey folks, I have not been cutting much in the heat, but took up some cutting a couple weeks ago when we had a morning under 80 deg for once.

First thing I did the night before was burn off the spark arrestor screen since so many blame that. We, it seems to help some. Made it through a tank of gas, and there was a little bogging, but never stalled out completely. The spark arrestor screen did not look badly carboned up, but must have been playing a role.

But I looked at the air filter. As much as it wasn't fully loaded or anything, it looked like it was the old fiber variety and it looked like it had gotten oily over the years. I decided rather than try and clean with solvent or gas, I'd get new one. The newer Stihl version seems made of just a polyester like cross hatch. Probably emits some smaller particles, but perhaps nothing large enough to cause problems downstream. Not like there is any crankcase oil in a 2 cycle!

OMG -- today ran the saw. The difference is amazing. Saw runs I swear better than new. Not my 194 or my heavy JDs, but sooo much better.

So there's closure on this post. Primary problem was a bad air filter. Spark arrestor likely playing a roll too.

So huge thanks to you all. I will certainly never be a regular contributor here, as I just don't have enough knowledge to really help anyone, but I sure appreciate people that do. My current passion is planting a 1000 oak trees after I retire. Have the land, learning how to plant acorns effectively and protect from deer and rodents. Its a challenge......
 
Well, I'm back. In colder weather, the problem is re-occurring. Does that help any of you guru's narrow it down?

In the meantime, I've checked the gas tank vent valve. Seems to work fine -- allowed me to suck in air, but not blow back out. Got a little gas my mouth as proof....

Air filter still fine. And I've only burned 2-3 tanks of gas since I burned off the spark arrestor screen, so doubt that's it.

Found maintenance manual online and have figured out how to get to the impulse tube. But have not broken down the saw that far yet. That's next.

Advice, given the seeming "reoccurrence" with cold weather......
 
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.
Never ever thought about spark arresters till I worked in a TNT plant. You learn a lot about a lot working around TNT. I read up on every piece of equipment I owned , trucks, cranes, welders, air compressors etc. and tagged every required device so they could readily see it. They wouldn't let me leave and I kept a crew in there for 2 years. This was around 83-84 they were mothballing it.
 
Wow, workbench is littered with parts. top handle saws more complicated, needed to remove the handle, flywheel etc. Impulse line is intact, no leak. Seemed like it allowed a bit more air movement after some carb cleaner through it. Since its such a rigamarole to get to, I think a trip to the Stihl dealer might be reasonable. Prolly a $5 part that they will want $20 for, but its 11 years old.....
 
Frustrated with parts availability. Just put it all back together and its running better. Perhaps the impulse line was a little plugged.

What I do know is that I am not gifted with chainsaw assembly. The way the 192TC top handle goes together makes putting stuff together like doing microsurgery. And I have huge hands and a tremor from early parkinsons... Getting the impulse line back onto the underneath side of the top handle assembly was painful. Literally. In the end, I ignored the Stihl manual instructions and assembled the top handle first, then removed the ignition coil to pull the impulse line down and onto its nipple behind the ignition and flywheel. Worked far better.

I might have to start hiring a professional.....
 
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.
He litterally stated he runs stihl synthetic oil, that garbage clogs arrestor screens
 
Frustrated with parts availability. Just put it all back together and its running better. Perhaps the impulse line was a little plugged.

What I do know is that I am not gifted with chainsaw assembly. The way the 192TC top handle goes together makes putting stuff together like doing microsurgery. And I have huge hands and a tremor from early parkinsons... Getting the impulse line back onto the underneath side of the top handle assembly was painful. Literally. In the end, I ignored the Stihl manual instructions and assembled the top handle first, then removed the ignition coil to pull the impulse line down and onto its nipple behind the ignition and flywheel. Worked far better.

I might have to start hiring a professional.....
Taking those stinkers apart is frustrating, glad I have several sizes/styles of hemostats. Any time im opening one of those up to the point the carb comes off it gets the side covers removed and pressure/vac tested, compression tested and cylinder fins cleaned because once I tear it apart I do not want to do it a second time! Their intake boots tear easily if any of the mounts break or even get stretched/sag. At that age Its safe to assume anything rubber, piston rings, carb guts etc needs replacement if you want another decade of trouble free use.
 
Taking those stinkers apart is frustrating, glad I have several sizes/styles of hemostats. Any time im opening one of those up to the point the carb comes off it gets the side covers removed and pressure/vac tested, compression tested and cylinder fins cleaned because once I tear it apart I do not want to do it a second time! Their intake boots tear easily if any of the mounts break or even get stretched/sag. At that age Its safe to assume anything rubber, piston rings, carb guts etc needs replacement if you want another decade of trouble free use.
Interesting you mention hemostat. Used several. Always worried I would collapse the internal spring on the impulse line, rendering the system inoperable. Not really clear just how tough that internal spring is.

I also blew things out good and proper. It seemed to work better after the exercise, but not clear just what I fixed. I also hit the carb with some spray, cleaned out the lines etc.

Dunno. I have the $$ for a new saw if needed. I just hate tossing repairable stuff. I am old school I guess. If I knew someone on Facebook Marketplace would fix it, maybe I should just sell next time its giving me trouble.........

Sometimes you got to accept your limitations.....
 
Interesting you mention hemostat. Used several. Always worried I would collapse the internal spring on the impulse line, rendering the system inoperable. Not really clear just how tough that internal spring is.

I also blew things out good and proper. It seemed to work better after the exercise, but not clear just what I fixed. I also hit the carb with some spray, cleaned out the lines etc.

Dunno. I have the $$ for a new saw if needed. I just hate tossing repairable stuff. I am old school I guess. If I knew someone on Facebook Marketplace would fix it, maybe I should just sell next time its giving me trouble.........

Sometimes you got to accept your limitations.....
The impulse hose does not contain a metal spring. Ask for the parts and repair manuals in the beg for manuals thread. Make a list and order everything needed for a soft rebuild and when stuff comes tear it apart, clean it and reassemble with the new parts. expect it to cost 200 bucks and a few hours of your time, you'll get another 10 years out of it for your effort.
 
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