261C stalling when hot - Video!

Ongoing issue with my Sthil 261. Hoping someone might point me in the right direction with it, so I've added a video link of how it's acting below.

It's 7 years old but hasn't seen a lot of use until fall of last year. It's an mTronic saw, not sure of what version since it's not listed, so it's likely a Gen-1 mTronic. It's spent the spring at the local Sthil dealer who swears up and down that it's a perfectly running saw. After three trips, they're just saying to 'use good fuel'. But after a few cuts (~3) through decent (~12") wood, it's gets hot and stops working. After it cools down FULLY, It'll do another few cuts and the cycle repeats.

Not sure if it's a chicken or egg issue: Maybe the issue that it's getting overheated? Or is the issue that it's not firing long when at temp?

Here's a video of how it's acting - be kind, it's only my 2nd youtube video!~



Any sage advice appreciated!

Thanks in advance, Cheers!

Try this,
Start the saw in the choke position and let it run for 60 seconds, then turn it off Do Not Hit The Throttle
If that does not work, then I advise let it cool down maybe even the next day
Start the saw in the choke position and let it run for 90 seconds, then turn it off Do Not Hit The Throttle

Now what type of gas are you using with your mix? I personally only use 93 octane so it sparks cleaner and hotter, but Stihl recommends minimum 89 octane in their equipment.
Do you use a good quality mix?

Hi @Stihl 99 ;

I did the 90-second mTronic reset earlier this spring to unfortunately no effect. I'll certainly try a 60-second version as well. If it works, I'll report it here for sure.

Gas-wise, it'll historically run (occasionally, but for many years) on 91-octane being the top that's available from the local Gen7 gas station + the Stihl oil mix at 50:1. But, because it was the initial reccomendation from my Stihl dealer (and I'm not discounting user-error here!), it currently running on the 50:1 pre-mix gas (Husqvarna, not Sthil but I've read they are interchangable.)

@Stihl 99 -- one point of clarity, when I did the mTronic reset, I let it run 90 in choke and THEN touched the throttle to release the switch from the choke position. (otherwise, the up/off switch position isn't accessible) But, I suppose I can also turn it off by pressing the decompression valve. Easily tested -- I'll have it back on the property this Saturday and report any success.

Update:

I was doing the mTronic reset wrong - I had the chain brake on previously. So, in repeating the process, I took it off and watched how it spun up the chain a few times. I did it twice last Saturday. 60 seconds, and then 90 seconds.

For good measure, I threw on another new chain, and my 2nd bar (which hadn't ever seen use prior) and only ran the pre-canned Husqvarna 95-octane fuel. Also was sure to blow out the air filter (the older black one) but it wasn't fouled at all. Also confirmed it oils up well.

It dawned on me that this saw, despite being 7 years old has never really been broken-in. So, I kept it to smaller wood for the first tank of fuel; 3" 4" limbs, or taking larger cuts in multple stages, never loading the saw -- each time letting the saw idle down for at least two minutes between cuts. Doing this, it would *sometimes* stay on after the cut though it'd still lean out, and then stall about half the time.

When it stalled, I'd restart it immediately instead of cooling dry (my thoery is that the oil's in the fuel, so idling down to cool might be better then sitting?) and in two/three pulls, it'd typically stay running.

Doing this idle-down routine after 2 or 3 no-load cuts allowed me to get through some actual work for the first time... though very VERY slowly.

The following Tuesday (Canada Day!) I was out again. Re-did the 90-second mTronic reset and had my fingers crossed that it'd take some actual load today.

Sadly, no improvement. If I load it (AT ALL) it'll finish the cut, idle for 30-seconds, lean out, and stall.

I just can't keep this thing running!

I know this saw can do more -- but for now, I'm getting more done with a neighbour's 170.

I'm not sure if my next steps are "buy a new saw?", a different break-in procedure, or throw parts at this one and hope something sticks. (Fuel line? Coil?)

Ok try this one and last one I had notes on
Start with the choke on and chain brake on
Let it idle for 30 seconds
Release the chain brake and hold it wide open for 30 seconds to see it it idles down by itself, if it does then you reset the M-tronic

@Stihl 99 -- I'm dumb enough to do that without hearing protection~ Gotta learn everything the hard way~.

It didn't idle down.

It's the first I've heard of that procedure, so I'll try to do some targeted research. But, is the scenerio pointing to the mTronic not taking a reset? I mean, I've tried every combination under the sun at this point, I so I would have thought.

Separately, I did find these two threads on arboristsite that seem to describe the same behavoir:

https://www.arboristsite.com/threads/ms261c-m-mtronic-issue.338623/ - No Resolution
https://www.arboristsite.com/threads/ms261-stalling-not-idling-m-tronic-issue.373936/ - Coil

I wonder if this coil is even replacable these days - it's version isn't labelled on the saw, so I can only assume it's 'pre-2.1'.

Yes the coil should be the same as newer versions. I am sorry this is happening, but after thinking about it if the coil is getting too hot this would cause it to shutdown, but I would think it would be faster than it is, it was the way the saw was behaving like you I thought it just needed a reset.

Jumping in here guys. I have a 1st gen 362C-M, about 12 years old I think. It had always been a fantastic strong running saw from new, but last year it developed an inability to run under load. It would start fine and idle fine and rev fine, but 5 seconds after putting it to work, it would fall flat on its face. It would either just stall out or if I released the throttle and pulled out of the cut fast enough, it would idle. If I carefully feathered the throttle, I could cut at half throttle. Multiple attempts at gen 1 reset got me nothing but frustration. Replaced fuel filter and spark plug. No change. Took it to the dealer, they said it failed the carb test and ordered a new carb and intake. Installed new carb and intake, but no improvement. Reinstalled old carb onto new intake and replaced M-tronic module. That was it. It runs like a new man. It may be the M-tronic.

It's been at another shop, this one in Toronto, for about 2 weeks. Thankfully, this shop is actually testing it and *IS* seeing the problem -- I think it's helped that it's been getting worse and really not taking any load whatsoever these days.

They say everything's starting/idling/testing fine, but then it leans out and stalls after seeing any load. They're asking for more diagnostics time & are swapping some parts around to see if they can figure out where the stall is coming from.

In the meantime, an uncle gave me old 270 which could use some tuning, but is a completely decent saw to get some actual work done. It's heavier but the longer bar (20") compensates for that nicely. Similar displacement, but the engine is a different animal from my 261 -- it's less 'spritely', less 'intense'. If I were doing firewood at a cottage, it might even be a preferrable machine. Still, I'm looking forward to getting my 261 back in hand.

WOW. Immediately go for the Mtronic!
Last place I would be looking.
You are losing fuel or spark- like any old 2 stroke eve produced.
Check spark when it quits- is it present?
Open the fuel cap-does it restart? Sure sounds like a vent issue.

Low hour saw with some years? Fuel issues are #1.
I would rather work on saws that use 5gallon of fuel a week than 1 gallon in a year.
But that is another LOOONG discussion that no one wants to hear.

Shop says the have it fixed. I'm not able to pick it up in the city for a few more weeks, but I'll update the thread on the work that was done, and how it's turning out. It'll be great to run my 261 again!

Give me my old Stihl 056 AV Super any day. May be heavy and not be as up market
as these Mtronic's but give it some choke two pulls and she is ready to go. cut for
as long as I like switch it off for smoko and couple of pulls and away again. Lot of
the arborist's out here in NZ are going back to the old stock standard stihl's.
Had one thee other day wanting to swap a mtronic for my Jonsered 930 av Super
but the answer was of course no thanks. Don't know why stihl changed to that in
chainsaws, always thought the saying was if it ain't broke don't fix it.

Mr. Leon, my name is Jake and I like every chainsaw but the competition to the 261c is the Husqvarna 545 mark II and I tell you what I've never run a 261 C but I've heard a lot of good things about it! But I'm say this I bought myself a 545 Mark 2 and that thing runs like a bat out of hell and you don't have to do nothing to it the calibration is a little bit different from the steel Electronics but that 5:45 is a great Soul it's fast it comes with a 20 inch bore which is a good length not too long not too short you can run that seat I believe it's the c83 new Husqvarna chain and it cuts like butter but as far as the chain goes I'm from the south nobody even knows what a square ground chain is but I sat there for about 2 months with a fall a double bevel file and learned how to make a round round a square ground and a pretty proud of myself I can make a pretty short freaking chain Square Ground beautiful cutter and it throws some shards of wood with that 545 so anyway I can Ramble On and On I'm sorry go buy you a 5:45 if you want a small lights all 50cc it'll burn that 261 out of the box thanks over and out Jake Broussard

Well, the Toronto shop held it for about a month. They swapped the fuel selonoid, and the chain (for some reason... a new chain for a new chain, meh)

The saw with the replacement fuel selonoid worked like it was in the spring. Instead of working for 2 minutes, it's back to working for ~10-minutes. But, it still falls flat on it's face. So. it's still not fixed.

New symption maybe: what causes a fuel selonoid to fail? I'm back to it overheating? maybe??

But, yeah, I'm $1,000 into fixing a $700 saw.... and it's still not working. I'm lucky to use it for a bit before having to swap to my older 270 - so I'm finally at a point where it's not leaving me high and dry. But I'm beside myself with multiple dealer's complete failure at figuring out what's happening with this saw. You would think there was a Stihl dealer network for escallation of rare malfunctions??? I mean, I went w/Stihl because of the reputation for quality and dealer network - but so far it's been a year or forking over more and more money with no gain. I'm so very frustrated with this saw!!!!!!!

I'd have sworn off the brand if the older 270 wasn't there to save the day. It's 10 years older and cutting circles around my pro saw~

It's hard to write-off something you've spent nearly $2k on. Do I bring it back a 8th time? Do I try yet another dealer? VERY FRUSTRATED.

OnOrbit Studio said:

Well, the Toronto shop held it for about a month. They swapped the fuel selonoid, and the chain (for some reason... a new chain for a new chain, meh)

The saw with the replacement fuel selonoid worked like it was in the spring. Instead of working for 2 minutes, it's back to working for ~10-minutes. But, it still falls flat on it's face. So. it's still not fixed.

New symption maybe: what causes a fuel selonoid to fail? I'm back to it overheating? maybe??

But, yeah, I'm $1,000 into fixing a $700 saw.... and it's still not working. I'm lucky to use it for a bit before having to swap to my older 270 - so I'm finally at a point where it's not leaving me high and dry. But I'm beside myself with multiple dealer's complete failure at figuring out what's happening with this saw. You would think there was a Stihl dealer network for escallation of rare malfunctions??? I mean, I went w/Stihl because of the reputation for quality and dealer network - but so far it's been a year or forking over more and more money with no gain. I'm so very frustrated with this saw!!!!!!!

I'd have sworn off the brand if the older 270 wasn't there to save the day. It's 10 years older and cutting circles around my pro saw~

It's hard to write-off something you've spent nearly $2k on. Do I bring it back a 8th time? Do I try yet another dealer? VERY FRUSTRATED.

Click to expand...

So I’m in the USA, not Toronto, but when my dealer replaced the carb on my saw for a new one and it wasn’t fixed, he removed the new carb, put the original back on, and didn’t charge me for the carb. Seems like that is the stand-up way to handle that situation. In my situation the M-tronic module was the culprit, and he did also install a new spark plug which I was ok with. But he did leave my well used chain in place. I think somehow you need a more ethical dealer than the two you’ve used. Once you find one, stick with him. Have you negotiated for satisfaction with these two dealers? They should have made it right.

OnOrbit Studio said:

It's been at another shop, this one in Toronto, for about 2 weeks. Thankfully, this shop is actually testing it and *IS* seeing the problem -- I think it's helped that it's been getting worse and really not taking any load whatsoever these days.

They say everything's starting/idling/testing fine, but then it leans out and stalls after seeing any load. They're asking for more diagnostics time & are swapping some parts around to see if they can figure out where the stall is coming from.

In the meantime, an uncle gave me old 270 which could use some tuning, but is a completely decent saw to get some actual work done. It's heavier but the longer bar (20") compensates for that nicely. Similar displacement, but the engine is a different animal from my 261 -- it's less 'spritely', less 'intense'. If I were doing firewood at a cottage, it might even be a preferrable machine. Still, I'm looking forward to getting my 261 back in hand.

Click to expand...

It is really too bad you are having this problem. My 25 year old 026 just keeps running. This m tronic business underwhelms me. Good luck.

Has anybody did a vacuum and pressure test on this saw? Sounds like a vacuum leak. You can fix carbs and modules all day, but a vacuum or pressure leak will never be cured.
AND Mtronic can only cover a leak to a point.
Just normal check on any two stroke ever made.
Also the 2 piece fuel lines will leak at the joint after time.

So, maybe I'm a glutton for ongoing punishment, but I've brought it back to the Toronto shop. I've relayed the comments here, but I think they landed on deaf ears -- It's a busy shop and they write the trouble ticket in 15-seconds or less. This time, instead of 'stalls', I protested and it's "leans when hot".

The first person I talked to understood that this was a return on a failed repair, but the second made no note of it - I just know they'll charge me for the investigation, again.

Well, we finally have an answer.

Sadly, not a good one; the crank case is cracked.

That's why it runs fine until it gets warm, at which point it losses it's vaccuum, runs hot, leans out and stalls. Store says come get it for parts, but don't put any more money into it.

It's amazing really -- the saw's not had a hard life.

Oddly, I'm probably going to replace it with another 261C -- I've got bars/chains for this that wouldn't be compatible with another brand. So, the question is (if anyone's interested in popping in) is mTronic or traditionally carborated?

Now we need to know- where is the crack?

STIHLTECH said:

Now we need to know- where is the crack?

Click to expand...

I'll pick it up on Friday, and see if I can grab a photo somehow. Not sure if it's re-assembled - hopefully I can grab an easy shot of it.

I have repaired many a outboard motor block that were cracked with Permatex. I'd give that a try before scrapping it.

OnOrbit Studio said:

Well, we finally have an answer.

Sadly, not a good one; the crank case is cracked.

That's why it runs fine until it gets warm, at which point it losses it's vaccuum, runs hot, leans out and stalls. Store says come get it for parts, but don't put any more money into it.

It's amazing really -- the saw's not had a hard life.

Oddly, I'm probably going to replace it with another 261C -- I've got bars/chains for this that wouldn't be compatible with another brand. So, the question is (if anyone's interested in popping in) is mTronic or traditionally carborated?

Click to expand...

My dealer talked me out of the Mtronic when I bought my 261 and i’m glad he did. I don’t normally use the saw at higher elevations and have had no issues with this saw.

OnOrbit Studio said:

I'll pick it up on Friday, and see if I can grab a photo somehow. Not sure if it's re-assembled - hopefully I can grab an easy shot of it.

Click to expand...

Hmm : cracked crankcase???
How did that happen??
Sounds fishy to me.
Once again, I agree with STIHLTECH,
Forget that it’s mtronic
Look at the basics fuel lines , vacuum pressure test

Just back from the shop.

I had asked about where he saw the crack and how this type of thing might have happened, but he said it's probably a crack in 'one of the seals' and that I could try replacing 2 seals and making sure everything else is sealed up. He said it's best to try this repair personally and that the shop doesn't tend to do such repairs because it's a piece of work and they cannot guarantee it'll leave repaired.

He quoted $150 for a 'shot-in-the-dark' attempt at the repair if the shop were to attempt it. Maybe I'm nieve, but $150 sounded like a fair gamble -- this was at least the first shop that's been able to replicate the issue, and my experiences with the particular person in the past have been generally positive. (I didn't get the vibe that he was attempting to extract another bit of money from an otherwise dead saw.)

So, I guess the story continues. Hopefully the'll find a smoking gun once they get into the crankcase.

" A crack in one of the seals"???
Sounds a little on the guessing side. It is or it isn't. Vacuum and pressure test. Should be normal diagnosis for a saw shop.
If I diagnosed like that, I would not be repairing saws. No guessing. Find it and prove. As any good tech would.
Nope, I am not perfect either. But part of repairing is finding the issue and showing to the customer.
Might be time for you to get into repairs. We will be glad to guide you.

Absolutely! The key to addressing faults lies in proper testing. Relying on guesswork just won't do and demonstrating the issue to the customer is an essential part of providing great service.

Had the itch to check on the status of the saw. Yes... 7 month later. (they got busy with snowblowers)

They say they have it fixed and running well. Sad to say my reaction is "I've heard that before."

They said it was the oddest thing -- the decompressor valve was bad. I'm not sure that makes sense to me, but I think either way I'll be taking it back and test it in the woods again after the snow melts to a point where I can get back in there. If it's still bad, I don't think it's going back... 2 years in the shop is approximately 2 years less a week too long.

I hope you have the problem solved