MS192C Compression and Troubleshooting Questions

[lone wolf]

Well, I don't throw stuff out so I'm going to fix it. I'll be honest I use this saw solely for clearing dirt bike trails as it is mounted on the front of my dirt bike. I'm seriously getting the urge to go electric however I'm not throwing this Saul way because almost every aspect of it is in such Mint condition so hard to see it go.

I will do whatever it takes to get it fixed however out of curiosity is it and
idea to just do the rings and measure the compression again? if it needs a cylinder and a piston I will do it however obviously if I can avoid the cost and still get a good result I would like to try it.

Let me know thoughts, thanks!

Look at the piston ,compression that low usually means damage.

 

[lucgallant]

Look at the piston ,compression that low usually means damage.

I will disassemble and post some good images.

 

[Hip replacement climber]

Look at the piston ,compression that low usually means damage.

Looking for a 200t rebuilder and read how you are the man to do it I’m not good with this I’m new I would like to chat about total rebuild

 

[lone wolf]

I will disassemble and post some good images.

Both sides.

 

[lucgallant]

Both sides.

Both sides of the piston? I'll post pictures of every surface for sure.

I was wondering, when it comes to ordering parts, do you guys know if the engine parts are kitted? The fiche shows you can order the piston with the cylinder, but is there a kit for piston, rings, crankshaft seals and bearings? I was planning on doing those also considering I don't really want to have this apart for a while...

Also that piston pin bearing is not listed separately, so I'm curious on how to obtain it.

 

[lucgallant]

Alright...... Here it goes! Let me know thoughts please! Appreciate the support! Couple posts due to max 10 files.

 

[lucgallant]

Second batch.

 

[lucgallant]

Final batch.

 

[lucgallant]

So I ordered some parts today. After looking at it long enough I settled on rings, crankshaft bearings and seals. And the piston pin in case. Can't get that bearing per the fiche and there was one Stihl source that I saw that send that the crankshaft including those bearings came as one assembly.

I'm open to opinions but there's no real scoring, the marks on there seem pretty superficial. Fingernail doesn't catch on any of it.

I'll reassemble and immediately do compression. Worst case I need to add more scope at that point but all I will have lost is some engine pan sealant.

 

[sean donato]

Im not seeing anything that screams bad news tbh. I think you'll be in good shape.

 

[lucgallant]

Im not seeing anything that screams bad news tbh. I think you'll be in good shape.

I'll definitely post the compression result afterward for recordkeeping purposes on this forum.

 

[Tobystihl]

Small end bearing is crimped into the con rod and is not replaceable, genuine Stihl pots and pistons are quite cheap for this model.

 

[lucgallant]

Hi all,

Sorry for the delay in responding, first set of rings from Stihl arrived broken.

In summary: Got new rings, piston pin, crankshaft bearings/seals. Put it all in. Used the plastic from a 2L coke bottle to get the piston/rings in, great experience (sarcasm)....

Failed the pressure test after I used Threebond 1184. The tube was old... Redid it with Yamabond 4 (Threebond 1215). I successfully pressure and vacuum tested at +7psi/-7psi via the intake manifold using the Stihl blocking plates, with the impulse line in place and all. I did the fuel tank as well to test that it holds pressure and not vacuum, was successful.

Immediately did a compression test once I got the recoil back on, got 90 psi again. Added some engine oil in the spark plug hole, got 125 psi. Completed the re-assembly. Went to start the saw, more or less the same behavior as before. Rechecked the compression, 75 psi. W.T.F. After reassembly it did seem to have a good compression when tugging on the cord, but now that it's at 75 psi it feels weak ... like 75 psi.

Anyway I've worked on motorcycles quite a lot, and this saw wasn't "difficult" to work on, but it certainly took a crap ton of time. And cost who knows, maybe $100 in rings/bearings/blocking plate. But anyway I don't like waste so I'm inclined to get it fixed but would love some opinion on next steps.

The cylinder looked OK, but maybe it was worn, causing this situation.

I've love to hear from someone that has an MS192C (or very similar model) in good working order to just take a quick compression reading. I would think it'd be close to my FS 38 trimmer at 140 psi but just guessing.

I'd really hate to buy a cylinder and piston but might if I need to - appreciate some feedback here. I'm so inclined to buy the battery operated version of a saw but I'm very much a completionist and I'm not letting this go. Thanks!

 

[lucgallant]

All, been a long time. So without any apparent solution to my problem I had gone ahead and ordered a new cylinder and piston. It came all the way from Germany or Austria apparently as it took 4 months to arrived. So I put the whole thing together today, went quite well after I even got the Stihl collar for the piston and rings, it went in like a breeze.

The saw starts up OK after doing the two choke routine as described in the book, but then stalls. Starts again, idles maybe 2-3 seconds, stalls. Finally after it got warm, it would rev up and function, but as soon as off the throttle it stalls.

• Crankcase pressure and vacuum tested at +/- 7 psi
  • Both engine on its own and in the saw with the Stihl intake adapter and exhaust rubber plate. The impulse line is in play as well with this adapter plate.
• Compression upon reassembly - 125 psi
• Fuel line pressure tested at 5 psi by pinching after inlet filter (not sure why the service manual calls this the fuel return line) - it's the one that is cone shaped coming out of the intake backplate
• Leakage test performed on carburator at 11 psi (this is on the port that goes to the actual return line)
• Carburetor is brand new from Stihl
• Fuel inlet filter is spotless (not new)
• Tank vent functions, holds vacuum and allows air out
• On visual, the impulse line looks fine during vacuum test (I don't see it collapsed)

I'm really at a loss and don't want toss this saw. I seem to have good spark, but the plug is practically dry. I can't help but think it's not getting fuel.

Would like any tips, please. Thanks in advance.

 

[lucgallant]

All, been a long time. So without any apparent solution to my problem I had gone ahead and ordered a new cylinder and piston. It came all the way from Germany or Austria apparently as it took 4 months to arrived. So I put the whole thing together today, went quite well after I even got the Stihl collar for the piston and rings, it went in like a breeze.

The saw starts up OK after doing the two choke routine as described in the book, but then stalls. Starts again, idles maybe 2-3 seconds, stalls. Finally after it got warm, it would rev up and function, but as soon as off the throttle it stalls.

• Crankcase pressure and vacuum tested at +/- 7 psi
  • Both engine on its own and in the saw with the Stihl intake adapter and exhaust rubber plate. The impulse line is in play as well with this adapter plate.
• Compression upon reassembly - 125 psi
• Fuel line pressure tested at 5 psi by pinching after inlet filter (not sure why the service manual calls this the fuel return line) - it's the one that is cone shaped coming out of the intake backplate
• Leakage test performed on carburator at 11 psi (this is on the port that goes to the actual return line)
• Carburetor is brand new from Stihl
• Fuel inlet filter is spotless (not new)
• Tank vent functions, holds vacuum and allows air out
• On visual, the impulse line looks fine during vacuum test (I don't see it collapsed)

I'm really at a loss and don't want toss this saw. I seem to have good spark, but the plug is practically dry. I can't help but think it's not getting fuel.

Would like any tips, please. Thanks in advance.

All, just to close this issue off....

I vowed not to let this saw go in the garbage and I have fulfilled that vow...

After a litany of troubleshooting I ended up replacing all inlet fuel lines and the intake boot, and the impulse line and the spring within it.
The saw works well now. What a journey. When I first started I had no idea how these little beasts do, but now I have "some" idea.

Also for the record, the cold compression was about 125 psi after 110 pulls, and hot compression seems to be about 90-95 psi. So back to the original inquiry, my original engine is probably fine.

Anyway in the process I couldn't help but film it and make a time lapse video. Check it out below!

 

[Wood Doctor]

Fabulous! Now all I have to do is figure out how to watch it at 10 times speed rather than 100 and then buy a Farmertec kit and build one from scratch. Well, heck, I could probably do it without the video. Good show!

Say, I wonder what it would have cost to have a Stihl dealer repair this saw? Just curious.

 

[lucgallant]

If a person endeavored to do both the fuel lines and impulse lines right off the hop should be just an hour's labour.... but for the whole engine rebuild it'd be at least 2.5 hours labour, took me 3.5... so say 250$ labour plus 150$ for engine parts, 60$ carb, 100$ in rubber components... 560$+?

Never worth it economically... Saw is $550 taxed in. Unless we value waste somehow of course...