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Author Topic: Stihl 261s Scoring Pistons  (Read 2277 times)

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Offline JaredR

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Stihl 261s Scoring Pistons
« on: August 06, 2020, 09:15:08 PM »
Hi all,

I'm new to the forum and looking for some answers. We recently started building handcrafted log homes so I went to the local Stihl dealer and bought a 261 C-M for our notching and small saw work. After using it a few days (less than 10 hours on the saw) it wasn't starting and obviously had a problem. Took it back to the dealer and he takes the muffler off and the cylinder and piston are scored badly (see photo)  and he said the only time he had seen that happen was from unmixed fuel. However, we are running Stihl mixture at the suggested ratio and because we have built a good relationship with him he decided to look into it further instead of just saying we ran straight gas in it. He called his "higher-up" who asked what we were using it for and when he heard it was for log building he said immediately that the usage was too light and the saw had somehow self-adjusted and was over-revving, burning itself up. (We do a lot of brushing and light cutting, running it at half throttle). Apparently they had ran into this before with the smaller C-M models and log builders.

While he is replacing the piston and cylinder under warranty I went ahead and bought a regular carburated 261 which we have been using and it's been running great. However, this afternoon my brother sent me a photo of the piston on the new one and said it's scored and not starting. I have no idea what is causing this. Do Stihls seriously self-destruct if not ran under constant load? I'll be taking the saw back to dealer tomorrow as well as our 15gal tank of mixed gas that we have been using but would like to get some outside thoughts on this.

Thanks very much!



 

Offline Al_Smith

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Re: Stihl 261s Scoring Pistons
« Reply #1 on: August 06, 2020, 10:42:44 PM »
Although it might be unpopular  i might throw my 2 cents in .First I assume it's a fresh air part transfer and assume it's set up for 50 to one oil to gasoline ratio.
From my perspective firstly 50 to one is too lean .Secondly the saw had to be tuned too lean .Thirdly using fresh air with no oil laden fuel is asking for trouble .Although you might blow most of the fuel out on  fuel laden transfer you leave the oil film on the cylinder .With fresh air it's less oil .
Now I know why they did it because of EPA mandates but that doesn't mean it's a good idea .-2 cents nothing more 

Offline ZeroJunk

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Re: Stihl 261s Scoring Pistons
« Reply #2 on: August 06, 2020, 11:32:56 PM »
I have read the physics on why regular carburated two cycle engines don't like being run at half throttle. It was written before M Tronic etc. had been conceived , so not sure how that applies. But, the carburetors can be quite lean at half throttle. I don't know that it would ever be a problem limbing because the end destruction is heat, so even if it is lean you wouldn't be at a duty cycle high enough to melt the piston. But, if you are just steady cutting a log at half throttle you would.

Offline joe_indi

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Re: Stihl 261s Scoring Pistons
« Reply #3 on: August 06, 2020, 11:33:36 PM »
50:1 on these saws is begging for trouble. Here I recommend customers to go for ' other oils' ratio which is 25:1. Going midway on these two would be a 30:1 for any oil. We don't have Mtronics here but the carburettor versions of stratified saws and usually to be on the safe side I adjust the carb more generously. This prevents over heating. We are working in 34 C temperature and for you to get your piston scoured like this the temperature needs to be much higher or the carb leaner

Offline Ianab

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Re: Stihl 261s Scoring Pistons
« Reply #4 on: August 06, 2020, 11:46:40 PM »
I have heard of chainsaw carving guys having issues due to running the saws at part throttle for extended periods. The carbs on a chainsaw are relatively simple affairs, and are basically set to run at full throttle, or idle, as long as both those work, it's usually OK. They don't have the complicated fuel maps that a fuel infected car engine uses. The mixture might be wrong at 1/2 throttle, but saws don't usually spend much time running like that. 

A richer fuel/air mix and a bit more oil might help, but it's likely down to the operator. They aren't intentionally abusing the saw, but it's just not designed to be run like that. Let it idle, or give it the revs.  You might only be cutting through 2" sticks, but give it a blip of full noise to do it. That way it's not running lean, overheating AND starving for oil. 
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Offline barbender

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Re: Stihl 261s Scoring Pistons
« Reply #5 on: August 07, 2020, 12:06:16 AM »
Sorry about your saws! While I don't like a 50:1 ratio, I sure doubt that's causing your issue. When I was was brushing and such log building, I tried to just continually blip the throttle, instead of holding it at continuous medium rpms. 
Too many irons in the fire

Offline Spike60

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Re: Stihl 261s Scoring Pistons
« Reply #6 on: August 07, 2020, 05:51:27 AM »
50:1 isn't best for any saw, but it's at that ratio that modern saws will remain emissions compliant. That's why everything is supposed to be run at 50:1. I'm a 40:1 guy for my stuff; both newer AT saws and the old girls in the collection. But the deal here isn't the ratio, it's the constant 1/2 throttle running.

I think that just about every saw's owners manual will say that cutting should be done at full throttle. Probably more of a safety concern than anything. As far as leaning out at constant part throttle use I can see that happening. Every carb has a "lo" speed circuit and a "hi" speed circuit. There is no provision in the carb for low RPM running. At part throttle use, neither the lo or hi speed can operate as they are designed to. And low RPM's results in less cooling air from the flywheel.

Solution here would be a good electric saw run off a generator on the job site. Would also eliminate exhaust fumes as the house starts coming together and you are working in tighter areas. I don't think that you or the dealer would want to take a chance on burning up a 3rd saw.
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Offline Patrick NC

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Re: Stihl 261s Scoring Pistons
« Reply #7 on: August 07, 2020, 09:36:19 AM »
Ive never had any problems with 50:1. I used it in my ms260 pro for 10 years without a problem. Now I run a Husqvarna 372xtorq and a 550xp mk2 with the same mix. No problem yet. I only use premium synthetic oil ( husqvarna xp+ ) and never mix more than 2.5 gallons at a time. I agree with the theory of running full throttle when cutting. 

Offline Al_Smith

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Re: Stihl 261s Scoring Pistons
« Reply #8 on: August 07, 2020, 09:45:24 AM »
Oh goody the oil wars again . 8)

Offline Patrick NC

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Re: Stihl 261s Scoring Pistons
« Reply #9 on: August 07, 2020, 09:52:50 AM »
Oh goody the oil wars again . 8)
Sorry, I wasnt trying to say what was right. Just relaying my experience. If never argue for someone change what works best for them. 

Offline Patrick NC

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Re: Stihl 261s Scoring Pistons
« Reply #10 on: August 07, 2020, 09:54:27 AM »
Autocorrect. I meant to say that Id never argue to change what works for someone else. 

Offline Al_Smith

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Re: Stihl 261s Scoring Pistons
« Reply #11 on: August 07, 2020, 11:34:43 AM »
 :D This great debate of oil mix and brand is a long standing type of debate going back as far as the internet and online forums .It can become amusing if you don't take it too seriously .

Offline JaredR

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Re: Stihl 261s Scoring Pistons
« Reply #12 on: August 07, 2020, 02:11:33 PM »
Thanks for all of the replies, guys!

I took the carb one to the dealer this morning and he is going to tear it apart. He's curious if both saws came from the same batch.

As far as cutting with a full throttle, I don't think that applies to brushing. I've been told to run about half throttle and "blip" it as @barbender mentioned.

I'm going to wait to hear back from him, and am hoping that the saw has a defect. If it doesn't I'm not sure what to do as we've been following instructions from more experienced sawyers and builders. I've even asked Robert Chambers about it and we were using it as he recommends.

Offline mike_belben

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Re: Stihl 261s Scoring Pistons
« Reply #13 on: August 07, 2020, 02:22:37 PM »
Saw carbs dont have much in the way of midrange metering circuits like a sled or bike. Its just idle and main jet, the midrange is just drilled passages at best.  

Id richen the mix and increase the idle time for cooldown breaks.  I sawmill with my 395xp at about 3/4 throttle all the time on the 87octane with the cheapest oil i can find, typically 30:1 and tuned fat.  I get a lot of vibration at WOT.  Lot of idle breaks to reject heat. 
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Offline lxskllr

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Re: Stihl 261s Scoring Pistons
« Reply #14 on: August 07, 2020, 03:02:11 PM »
Is that common knowledge saws shouldn't be run at 1/2 throttle? First I've heard of it. That should probably be put in the manual, with the reason given, instead of a generic "Cuts should be made at full throttle". I've run my mill at half throttle with the intent of letting it cool down a bit before going WOT again. Sounds like that's a bad idea.

Offline gspren

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Re: Stihl 261s Scoring Pistons
« Reply #15 on: August 07, 2020, 03:21:57 PM »
I never heard or at least don't remember the why but my chainsaw mechanic said the throttle should be used like a light switch, all on or off.
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Offline JaredR

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Re: Stihl 261s Scoring Pistons
« Reply #16 on: August 07, 2020, 03:35:20 PM »
Is that common knowledge saws shouldn't be run at 1/2 throttle? First I've heard of it. That should probably be put in the manual, with the reason given, instead of a generic "Cuts should be made at full throttle". I've run my mill at half throttle with the intent of letting it cool down a bit before going WOT again. Sounds like that's a bad idea.
Same here. I'm also hearing a lot of conflicting info from multiple sources. The manual only says that you shouldn't run WOT until you use about 5 tanks. I didn't see anything about damaging it if used at 1/2. So apparently don't run it WOT or at 1/2, and if you do run it make sure it's under full load at all times. Or chance it burning up.  smiley_furious3 I think I will be seriously looking into battery chainsaws.

Offline Al_Smith

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Re: Stihl 261s Scoring Pistons
« Reply #17 on: August 07, 2020, 03:49:39 PM »
 After I rebuild a saw I tune it fat,run a few tanks like that .Then lean it out and flog it like a rented mule .I don't baby them .

Offline Real1shepherd

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Re: Stihl 261s Scoring Pistons
« Reply #18 on: August 07, 2020, 05:01:10 PM »
On the Swedish saws....no reason to baby them new or after a rebuild. Use a good oil mix and run them like you're gonna use them, hard.

As been said above, an electric saw is less bulky and gets into smaller spaces. Running a chainsaw half throttle most of the time is not getting enough oil mix in the works.

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Offline JaredR

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Re: Stihl 261s Scoring Pistons
« Reply #19 on: August 07, 2020, 05:04:24 PM »
So are there any log builders here who have some input? How do you run your saws when notching and have you had this issue?

Offline sawguy21

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Re: Stihl 261s Scoring Pistons
« Reply #20 on: August 07, 2020, 07:44:30 PM »
I have seen problems running at part throttle under load, the fan is not directing enough cooling air over the cylinder. The clutch also tends to slip and overheat. This is a real issue with trimmers/brushcutters. Run a 2 stroke like ya stole it, it also reduces the risk of kick back.
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Offline ladylake

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Re: Stihl 261s Scoring Pistons
« Reply #21 on: August 08, 2020, 04:22:06 AM »
I've been running my trimmer at half throttle for 30years and it still works great.  Maybe its how they are tuned, I'd bet a little rich low helps, plus a little rich on high also. Too many now days are tuned on the edge of being lean, for sure the auto tune machines as they need to get by the EPA as they're sent out . Steve
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Offline Al_Smith

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Re: Stihl 261s Scoring Pistons
« Reply #22 on: August 08, 2020, 08:30:25 AM »
On that lean run thing about 2 years ago before I retired I fixed one of those .It was a nearly brand new Echo about 50 cc's that never ran right,box store thing.
It had limiters on the jet screws .It was a simple task to just remove the tabs and tune it correctly . I've heard a dealer can't tamper with them .Last I knew I wasn't a dealer.It was set so lean it didn't have any power .It takes fuel to make power .
For a little saw it really ran pretty good.That little task was so simple the charge on that one was a 12 pack,not a case of beer . ;D

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Re: Stihl 261s Scoring Pistons
« Reply #23 on: August 08, 2020, 08:37:07 AM »
On the above about an Echo saw don't be fooled by a name .That one was really a nice little saw after I tuned it and I have a nice weed wacker as well ..
I have another which is about 2 cubic inch rear handle chainsaw used by a tree trimmer until it suffered a fall like Humpty Dumpty .Broke the shock mounts .I repaired it ,rebuilt the carb etc .It is not a bad saw at  all,so old it runs 1/4" chain .Never judge a book by it's cover .

Offline lxskllr

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Re: Stihl 261s Scoring Pistons
« Reply #24 on: August 08, 2020, 08:44:59 AM »
My two echos are my favorite saws; especially my 2511t. I like my Stihls a lot, and feel I got what I paid for, but it feels like the echoes(I'm always a little uncertain how to pluralize the brand) gave me more than I paid for.

Offline ladylake

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Re: Stihl 261s Scoring Pistons
« Reply #25 on: August 08, 2020, 03:01:45 PM »
 I have lots of Echo saws that run as good as any per cc.  They need the muff opened up a little and tuned good.  Steve
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Offline Air Lad

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Re: Stihl 261s Scoring Pistons
« Reply #26 on: August 08, 2020, 06:53:03 PM »
I've been running my trimmer at half throttle for 30years and it still works great.  Maybe its how they are tuned, I'd bet a little rich low helps, plus a little rich on high also. Too many now days are tuned on the edge of being lean, for sure the auto tune machines as they need to get by the EPA as they're sent out . Steve
On that, I was using my old (29yrs)Kawasaki,ex council whipper snipper yesterday. The thing is, I like to run 1/2 throttle at times also but it occurred to me that this machine has the old motorcycle round slide type carby. Mabye they have better oil distribution at medium revs compared to modern carbs

Offline mike_belben

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Re: Stihl 261s Scoring Pistons
« Reply #27 on: August 08, 2020, 10:57:50 PM »
Slide carbs meter the midrange by the taper and depth of the main jet needle so you can dial in a safe A/F ratio for the load.  Granted ya gotta actually tune them for the conditions.  

Anything thats only got high and low adjustment generally isnt gonna be ideal in the middle.
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Offline JaredR

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Re: Stihl 261s Scoring Pistons
« Reply #28 on: August 09, 2020, 12:34:54 AM »
Do chainsaw carvers use full throttle all of the time and have a full load? Is it expected behavior for a brand new product to fail this easily? Less than 5 hours of actual run time and only a 3rd of that at half throttle. 

Offline Ianab

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Re: Stihl 261s Scoring Pistons
« Reply #29 on: August 09, 2020, 04:44:02 AM »
It's a known problem. When you combine the low oil ratio, an already lean mix from the factory, lower revs giving less cooling, and a bit of bad luck.... I bet it's possible to kill a saw in one tank of gas. It's only got to run too lean for a few minutes, overheat once, and the damage is done. 

Like the guys mention, 2 stroke motorbikes have a more sophisticated carby, because they are expected to be able to cruise at 1/2 revs / 1/2 throttle all day. 

It can likely be compensated for by using a bit more lube and re-tuning the carb so it's slightly rich. But I think how the saw is being operated is the main issue. The "treat it like a light switch" comment is good advice. If you try and hold a light switch 1/2 on, it will soon burn up too. 

The problem may not occur with every model of saw, but that's more good luck than anything else. 
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Offline Al_Smith

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Re: Stihl 261s Scoring Pistons
« Reply #30 on: August 09, 2020, 05:15:29 AM »
You really can't compare a slide carb like an old Amal with a Tillotson carb on a chainsaw .If you really look at a Tillotson on a chainsaw it is in essence a mechanical fuel injector .It has to be to be able to run in all positions .
Some real old chainsaws had float carbs but the positions were very limited where they could be used on . 

Offline farmfromkansas

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Re: Stihl 261s Scoring Pistons
« Reply #31 on: August 09, 2020, 11:58:21 AM »
I had an 026 and the cylinder scored.  The dealer told me the 260's run faster than the 290's and have a lot of trouble with scoring. Heat builds up at higher speeds. The 290 I bought years ago has been nearly trouble free, so just run it and the 250. Helps to trade off on your saws to avoid overheating.

Offline mike_belben

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Re: Stihl 261s Scoring Pistons
« Reply #32 on: August 09, 2020, 12:07:52 PM »
Do chainsaw carvers use full throttle all of the time and have a full load? Is it expected behavior for a brand new product to fail this easily? Less than 5 hours of actual run time and only a 3rd of that at half throttle.
No, thats pretty sad.  
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Re: Stihl 261s Scoring Pistons
« Reply #33 on: August 09, 2020, 12:44:07 PM »
What your dealer failed to tell you about the 024's and 026's  is the fact they came with three different mufflers .Standard ,quiet and real quiet . 
I have an 024 that was in the dealers dead pile,slightly cooked piston .I never did one thing to it except attack the muffler and it runs just dandy ..The guy who  walked out after a trade in ended up with a 290 .He really didn't know any better. 
These things are made to run .However if you hold all that heat in with a restrictive muffler you're bound to bind them up eventually .They are not that loud with a worked over muffler but you certainly would not run them in your garage . :)  

Offline JaredR

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Re: Stihl 261s Scoring Pistons
« Reply #34 on: August 09, 2020, 01:12:54 PM »
It's a known problem. When you combine the low oil ratio, an already lean mix from the factory, lower revs giving less cooling, and a bit of bad luck.... I bet it's possible to kill a saw in one tank of gas. It's only got to run too lean for a few minutes, overheat once, and the damage is done.

Like the guys mention, 2 stroke motorbikes have a more sophisticated carby, because they are expected to be able to cruise at 1/2 revs / 1/2 throttle all day.

It can likely be compensated for by using a bit more lube and re-tuning the carb so it's slightly rich. But I think how the saw is being operated is the main issue. The "treat it like a light switch" comment is good advice. If you try and hold a light switch 1/2 on, it will soon burn up too.

The problem may not occur with every model of saw, but that's more good luck than anything else.
The thing is, I've talked to several builders who use their saw at half throttle quite a bit. And from what I've heard you shouldn't run at full throttle while doing light work like brushing.

Offline barbender

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Re: Stihl 261s Scoring Pistons
« Reply #35 on: August 09, 2020, 01:27:05 PM »
I have a couple of saws I used on a log building project. One burned down (Husky 346xp) due to a defective carb intake boot. There was a factory bulletin on it, and I brought it in several times and told him it acted like it had an air leak. It had a bog and wouldn't respond to the screws. The mechanic would take it and tune it for me🙄 It finally burned down, and they immediately asked, "aren't you log building?". I was about ready to choke the guy. He rebuilt it, I said "what about the air leak that caused this?". His answer was, "yeah, sometimes just taking them apart and putting them back together will fix that". I am not kidding. Obviously I don't buy anything there anymore. Anyways, I finally found the carb boot on my own, went to a different dealer and they said, "yeah there's a service bulletin and an updated part for that."🤦‍♂️ My point in all of this is, the dealer will often try to blame it on you when it is a defective saw. Mine melting had nothing to do with how I was using it. 

  If you're blipping the throttle vs just holding it at a certain rpm with low load, I don't see a problem. I could see the smart carb 261 maybe having an issue overcompensating, but log builders have been doing it that way for a long time and I think they expect better service life than one tank. At the very least I'd run 32:1 or so for oil. Good luck, I hope you get it figured.
Too many irons in the fire

Offline JaredR

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Re: Stihl 261s Scoring Pistons
« Reply #36 on: August 09, 2020, 01:35:51 PM »
I have a couple of saws I used on a log building project. One burned down (Husky 346xp) due to a defective carb intake boot. There was a factory bulletin on it, and I brought it in several times and told him it acted like it had an air leak. It had a bog and wouldn't respond to the screws. The mechanic would take it and tune it for me🙄 It finally burned down, and they immediately asked, "aren't you log building?". I was about ready to choke the guy. He rebuilt it, I said "what about the air leak that caused this?". His answer was, "yeah, sometimes just taking them apart and putting them back together will fix that". I am not kidding. Obviously I don't buy anything there anymore. Anyways, I finally found the carb boot on my own, went to a different dealer and they said, "yeah there's a service bulletin and an updated part for that."🤦‍♂️ My point in all of this is, the dealer will often try to blame it on you when it is a defective saw. Mine melting had nothing to do with how I was using it.

  If you're blipping the throttle vs just holding it at a certain rpm with low load, I don't see a problem. I could see the smart carb 261 maybe having an issue overcompensating, but log builders have been doing it that way for a long time and I think they expect better service life than one tank. At the very least I'd run 32:1 or so for oil. Good luck, I hope you get it figured.
Thanks for the info on this. Fortunately this dealer seems to be willing to work with us, as he is kinda scratching his head as well.
I'm going to wait until I hear back on what he finds out when he tears it apart and I'll post it up here. I just had no idea that saws are so finicky and in my experience poorly designed.

Offline barbender

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Re: Stihl 261s Scoring Pistons
« Reply #37 on: August 09, 2020, 01:44:35 PM »
They're usually not that finicky, in my experience. Something is amiss.
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Offline btulloh

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Re: Stihl 261s Scoring Pistons
« Reply #38 on: August 09, 2020, 01:46:13 PM »
I hope things work out on the saw.  This is all pretty surprising and new to me.  I get the full-throttle thing for normal use in felling or bucking or even trimming limbs, but doing the kind of work you're talking about is not a full-throttle or idle situation, and there are lot's of people doing joinery or carving.  Stihl makes carving bars and seems to know that market, and they are pretty good in general.  Seems like there would be some recommendations or guidance from the factory (like designers or engineers with actual knowledge) about these less than WOT uses.  Mixture, tuning, or something.  This just doesn't sound like it should be a problem when the saw is running almost unloaded.

(Did @HolmenTree check in on this topic?  He knows some stuff!)

Looking forward to your happy resolution and some real answers about using the saws like this.


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Re: Stihl 261s Scoring Pistons
« Reply #39 on: August 09, 2020, 01:52:05 PM »
Yea, this thread's kinda blown my mind. I thought I had the saw thing figured out, and now a bunch of people are saying "Yea, doing x isn't good...". I'd love to hear from an engineer on it.

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Re: Stihl 261s Scoring Pistons
« Reply #40 on: August 09, 2020, 01:58:16 PM »
Yea, this thread's kinda blown my mind. I thought I had the saw thing figured out, and now a bunch of people are saying "Yea, doing x isn't good...". I'd love to hear from an engineer on it.
Yeah, same here. I've used saws for cutting firewood and some misc stuff, but this is the first time I'm seriously using them. I really enjoy learning new stuff but this one has been kind of baffling and I think a lot of the advice I've been getting is from people who don't really know their stuff.

I hope things work out on the saw.  This is all pretty surprising and new to me.  I get the full-throttle thing for normal use in felling or bucking or even trimming limbs, but doing the kind of work you're talking about is not a full-throttle or idle situation, and there are lot's of people doing joinery or carving.  Stihl makes carving bars and seems to know that market, and they are pretty good in general.  Seems like there would be some recommendations or guidance from the factory (like designers or engineers with actual knowledge) about these less than WOT uses.  Mixture, tuning, or something.  This just doesn't sound like it should be a problem when the saw is running almost unloaded.

(Did @HolmenTree check in on this topic?  He knows some stuff!)

Looking forward to your happy resolution and some real answers about using the saws like this.


Thanks, me too! That's actually the main reason I'm getting ticked off is the seeming negligence on Stihl's side. If their saws are this finicky at least their dealers should be aware of it and warn people.

Thanks for calling someone else in, I'm really wanting to hear from someone knowledgeable.  smiley_beertoast

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Re: Stihl 261s Scoring Pistons
« Reply #41 on: August 09, 2020, 02:01:20 PM »
Just poking around looking for any factory info.  Found two pertinent references - one on m-tronic web page, one video about m-tronic.

Web info says "adjusts to all external conditions".  Video says m-tronic adjusts fuel/air mix to any rpm's.  Keep in mind, these are both SALES related, not engineering.  Sometimes the sales end of things can embellish to suit THEIR needs though companies like Stihl and Husky can't really afford to have a big mis-match between sales claims and actual performance.  Too much at stake.

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Re: Stihl 261s Scoring Pistons
« Reply #42 on: August 09, 2020, 02:07:21 PM »
I'm really wanting to hear from someone knowledgeable


Just to keep from rustling any feathers, a lot of the people who've responded are knowledgeable and experienced.  None of us knows everything about some of this new tech and we're all doing our best keep up with it.  Most experience is going to be with standard carbs and screw-driver tuning, cause that's what's been around a long time.

My personal experience with M-tronic is that it works fine for anything I've done and I've never really thought about anything other than starting the saw and doing what I need to do.  I do follow their directions on cold-start and hot start, but that's about it.  (I've finally gotten old enough to realize that procedures in equipment manuals provide useful advice. :D)

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Re: Stihl 261s Scoring Pistons
« Reply #43 on: August 09, 2020, 02:46:50 PM »
Just poking around looking for any factory info.  Found two pertinent references - one on m-tronic web page, one video about m-tronic.

Web info says "adjusts to all external conditions".  Video says m-tronic adjusts fuel/air mix to any rpm's.  Keep in mind, these are both SALES related, not engineering.  Sometimes the sales end of things can embellish to suit THEIR needs though companies like Stihl and Husky can't really afford to have a big mis-match between sales claims and actual performance.  Too much at stake.
So in my mind that's how a self-adjusting piece of a equipment should be designed to work, but I'm being told that they apparently can self-adjust to self-destruct. I thought the idea behind the M-Tronic "improvement" was to minimize the knowledge need to run a saw. Especially relating to adjusting the carb.

I'm really wanting to hear from someone knowledgeable


Just to keep from rustling any feathers, a lot of the people who've responded are knowledgeable and experienced.  None of us knows everything about some of this new tech and we're all doing our best keep up with it.  Most experience is going to be with standard carbs and screw-driver tuning, cause that's what's been around a long time.

My personal experience with M-tronic is that it works fine for anything I've done and I've never really thought about anything other than starting the saw and doing what I need to do.  I do follow their directions on cold-start and hot start, but that's about it.  (I've finally gotten old enough to realize that procedures in equipment manuals provide useful advice. :D)
That comment was in regard to the conflicting advice I've heard from multiple sources, not all on this site. Supposedly saws should be ran WOT, but they also shouldn't, they should always be fully loaded or they will not last, but log home-builders use them like this regularly. It's like a can of worms and I expected better advice considering saws have been around for a long time.  ???

I understand the newness to M-Tronic, but please bear in mind that the second saw to do this was a regular carbed model.


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Re: Stihl 261s Scoring Pistons
« Reply #44 on: August 09, 2020, 02:57:07 PM »
Chainsaws seem to bring out some of the same people that can't behave when religion and politics come up for some reason. They usually don't last long here because this site is tightly moderated but for instance, take a subject like oil mix ratio. Some will be on the run it rich side, others will be proponents of 100:1 or your fuel/air ratio will be too lean and burn up your saw (and you may even suffer eternal punishment)😂 So there's a lot to sort through. I'd say stick with the advice of those doing similar work with the same saws, see if you're doing something different. Check your gas/oil mix again. It is very suspect being you had TWO saws melt down immediately.
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Re: Stihl 261s Scoring Pistons
« Reply #45 on: August 09, 2020, 03:03:47 PM »
That comment was in regard to the conflicting advice I've heard from multiple sources, not all on this site


I understood your original comment.  Just trying to head off any potential misunderstanding.  

This is a useful discussion, and hopefully it will lead to a definitive answer.

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Re: Stihl 261s Scoring Pistons
« Reply #46 on: August 09, 2020, 03:10:18 PM »
Chainsaws seem to bring out some of the same people that can't behave when religion and politics come up for some reason. They usually don't last long here because this site is tightly moderated but for instance, take a subject like oil mix ratio. Some will be on the run it rich side, others will be proponents of 100:1 or your fuel/air ratio will be too lean and burn up your saw (and you may even suffer eternal punishment)😂 So there's a lot to sort through. I'd say stick with the advice of those doing similar work with the same saws, see if you're doing something different. Check your gas/oil mix again. It is very suspect being you had TWO saws melt down immediately.
Oh, I think that's any subject.  :D I was hoping some log builders would weigh in, and I appreciate your advice. I think these saws are defective. 
I have checked my mix, believe me. :D And as I've told others, our 661 C-M is running the same exact gas from the same containers, has about twice as much time on it as the two 261s, and has had no issues.

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Re: Stihl 261s Scoring Pistons
« Reply #47 on: August 09, 2020, 03:15:50 PM »
That comment was in regard to the conflicting advice I've heard from multiple sources, not all on this site


I understood your original comment.  Just trying to head off any potential misunderstanding.  

This is a useful discussion, and hopefully it will lead to a definitive answer.
I understand, thanks!
Same here. I'm hoping between you guys and some others sources I'm tapping into we can figure it out. I don't want to mess up another saw, and being a small business taking on a new line of work cash is tight without all of this. I just want to find out what the problem is as I know people use these saws to do this work and have for years. Shoot, if we had not been mixing our fuel I would be happy as I would at least know what was wrong.

Offline mike_belben

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Re: Stihl 261s Scoring Pistons
« Reply #48 on: August 09, 2020, 04:59:27 PM »
Cmon @barbender ive been behaving this time.   Now if you dont know 100:1 is proven to save 1.3 polar bears per day youre an idiot!
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Offline mike_belben

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Re: Stihl 261s Scoring Pistons
« Reply #49 on: August 09, 2020, 05:02:43 PM »
To the OP,  have you got an infrared temp gun?

Pistons transfering to jugs is entirely a temp thing and you should get in tune with that concept asap before cooking another.  Richen your mix, richen your screws, increase your cool down breaks by idling it flat on the floor periodically.  And beware the clutch bearing needs manual lubrication now and then.  It is engaged any time the chain isnt.
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Re: Stihl 261s Scoring Pistons
« Reply #50 on: August 09, 2020, 07:11:30 PM »
Is there or would there be an advantage to the 261 without the C or CM? My 261 which I am quite fond of is the plain 261 without the computer. Also exactly what is "brushing" that's been mentioned several times?
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Re: Stihl 261s Scoring Pistons
« Reply #51 on: August 09, 2020, 08:33:11 PM »
These saws aren't 4 strokes you can't expect them to get proper air cooling and lubrication at half throttle.
I think a 50cc saw is way too small for log building. A log builder I know up here only uses 372XP saws.

If you don't want to swing a 372 or 461 then get a Stihl electric plug in saw then you'll have some good slower rpm power with all the torque you need and not have to worry about burning up pistons  :D
Making a living with a saw since age 16.

Offline JaredR

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Re: Stihl 261s Scoring Pistons
« Reply #52 on: August 09, 2020, 11:43:40 PM »
To the OP,  have you got an infrared temp gun?

Pistons transfering to jugs is entirely a temp thing and you should get in tune with that concept asap before cooking another.  Richen your mix, richen your screws, increase your cool down breaks by idling it flat on the floor periodically.  And beware the clutch bearing needs manual lubrication now and then.  It is engaged any time the chain isnt.
Thanks for the suggestions. I do have a IR gun, what temps should I be looking for and where on the saw?

Also exactly what is "brushing" that's been mentioned several times?
How to Notch a Log for Building a Log Home or Log Cabin Saddle Scribe Style 346xp - YouTube

These saws aren't 4 strokes you can't expect them to get proper air cooling and lubrication at half throttle.
I think a 50cc saw is way too small for log building. A log builder I know up here only uses 372XP saws.

If you don't want to swing a 372 or 461 then get a Stihl electric plug in saw then you'll have some good slower rpm power with all the torque you need and not have to worry about burning up pistons  :D
46 to 55cc is the recommended size for notching as it's easy to work with. This is the size recommended by pro log builders. I've actually strongly considered an electric one, but I hate cords and I don't think the battery ones are good enough. Yet. And log builders have been using saws for years.


Offline barbender

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Re: Stihl 261s Scoring Pistons
« Reply #53 on: August 10, 2020, 12:05:18 AM »
I'm far from an expert, I built one log shell that I ended up not even using. This was my experience. A 50cc saw is a nice size for notching and cutting lateral grooves. I suppose it depends on how big of logs you are using. As far as brushing and that sort of thing, as I mentioned when I did it I would continually blip the throttle. Not much different than how I run a saw when I'm limbing, I don't know about the rest of you but I don't hold the throttle wide open and walk down the tree🤔😁 The bigger saws got used for ripping cuts and cutting out window and door openings.
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Re: Stihl 261s Scoring Pistons
« Reply #54 on: August 10, 2020, 12:15:14 AM »
I'm far from an expert, I built one log shell that I ended up not even using. This was my experience. A 50cc saw is a nice size for notching and cutting lateral grooves. I suppose it depends on how big of logs you are using. As far as brushing and that sort of thing, as I mentioned when I did it I would continually blip the throttle. Not much different than how I run a saw when I'm limbing, I don't know about the rest of you but I don't hold the throttle wide open and walk down the tree🤔😁 The bigger saws got used for ripping cuts and cutting out window and door openings.
Same as our use. I guess we weren't blipping enough.  :D

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Re: Stihl 261s Scoring Pistons
« Reply #55 on: August 10, 2020, 01:36:10 AM »
Cmon @barbender ive been behaving this time.   Now if you dont know 100:1 is proven to save 1.3 polar bears per day youre an idiot!
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Re: Stihl 261s Scoring Pistons
« Reply #56 on: August 10, 2020, 06:57:55 AM »
Cmon @barbender ive been behaving this time.   Now if you dont know 100:1 is proven to save 1.3 polar bears per day youre an idiot!
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Re: Stihl 261s Scoring Pistons
« Reply #57 on: August 10, 2020, 09:57:35 AM »
I would buck a few rounds at WOT then measure wherever you can get the IR gun to repeatably and fast.  Be it the fins or muffler port.  The exhaust side of the piston always melts first.  

Anyway, get a baseline from "normal operation" and also see how much idle time it takes to shed say, 100F.  you can then quantify just how badly the saw performs while whittling your cabin logs.

This info may also help you in fighting stihl if needed.  I would video record it.

I think youre gonna need to open up these mufflers to get the temps down.  If sound waves reflect they cancel out so u can increase flow and expel heat without extra noise.  I cut a slit, bend it, then weld a little louver over it to make the exhaust change directions back at itself.  Works great.
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Re: Stihl 261s Scoring Pistons
« Reply #58 on: August 10, 2020, 04:17:04 PM »
 
 I'd get a saw without auto tune and tune it rich.  Steve
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Re: Stihl 261s Scoring Pistons
« Reply #59 on: August 10, 2020, 04:56:59 PM »
Well Jared; I can understand your frustration but you're veering away from asking for advice to venting your frustrations here at those who post replies that don't conform to your hoped for narrative that there is something wrong with those saws. You certainly don't want to hear that bad news from Stihl, but if you throw out a question like this you will undoubtedly get some answers you don't like. And it should be expected that the answers will vary widely. As you admit that you are kind of new to this yourself, you aren't in that strong of a position to judge those who give an answer you don't like as not knowing what they are talking about.

Everything about these saws lives under a microscope here on these sites. Granted, 100% of your saws have burned up. But that's just 2 saws. If there were any known issues with 261's failing that quickly it would be well publicized in these parts. Us Husky guys would love to be able to say that the 261 is junk, but it is a well received saw with a pretty solid reputation. (I know I just said something nice about Stihl, it must be the 95 degree heat. :))

Ultimately, this needs to be hashed out at the dealer. Sounds like he is a decent dealer and Stihl does stand behind their products. You might not get the answer you want, but we all run into that now and again. Also, some newer saws may, and likely do, react differently to part throttle operation than older models. So, only similar experiences with 261's can be useful examples.
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Re: Stihl 261s Scoring Pistons
« Reply #60 on: August 10, 2020, 07:50:20 PM »
This past Saturday I went with a nephew to my local Stihl dealer who happens to be Amish and he only sells the non auto-tune, he was out of 261s and 660s, can't get them fast enough, I wonder if the plain 261 without auto-tune and set a bit rich would solve all your problems. I'm no mechanic but I would think maybe a manual adjustment might be better.
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Re: Stihl 261s Scoring Pistons
« Reply #61 on: August 10, 2020, 08:06:49 PM »
Had a bit of a scare with AK a month or so ago. I use their Stihl site to check specs on saws cause you gotta use something, and I figured I'd give them the hits for whatever that's worth. They were no longer listed! Searching Stihl's site they don't show up either. Had a job up that way, and I stopped in. He said it was news to him. He had a bunch of new stuff in front of the shop that just got delivered. Big relief! I was trying to figure out who I'd go to. Bought a couple rim sprockets, and I'm just happy he's still around.

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Re: Stihl 261s Scoring Pistons
« Reply #62 on: August 11, 2020, 09:33:53 AM »
This past Saturday I went with a nephew to my local Stihl dealer who happens to be Amish and he only sells the non auto-tune, he was out of 261s and 660s, can't get them fast enough, I wonder if the plain 261 without auto-tune and set a bit rich would solve all your problems. I'm no mechanic but I would think maybe a manual adjustment might be better.
You can still buy the non auto-tune saws from a dealer? When I asked last fall about a 660 they said they were no longer made. I know you can buy a knock off 660. 

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Re: Stihl 261s Scoring Pistons
« Reply #63 on: August 11, 2020, 02:03:53 PM »
Having a 261CM and knowing quite a few others who also do and use them in a wide variety of applications from hard and abusive forestry to babied home hobby uses, and all that I know of, loving their saws, I find it hard to believe the stories that make it sound here like there is an inherent problem with either the CM or older adjustable carb models.
I have always mixed my own saw fuel with the best gas I could find and Stihl synthetic oil at 40:1 and I've never had an issue figuring I was a bit OCD considering many I know only use whatever regular gas and no name regular oil, yet I have never heard any of them having issues either despite what I mentioned would be considered very hard and borderline abusive situations!
Makes you wonder if the recommended 50:1 ratio is somewhat suspect as some seem to allude to, how Stihl would react if someone told them their canned gas and oil - had the potential for owners burning up their own saw models?
Its too bad that someone with a connection to Stihl themselves wouldn't chime in and respond to what appears to be alarmist rumors regarding one person's bad experiences with the brand - as it tends to try and tarnish all of the probably millions of unheard of, reliable and durable saws and their stories of that model, that have served and continue to, their owners so well in all types of uses and situations..
Just Say'n..   :)

Offline mike_belben

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Re: Stihl 261s Scoring Pistons
« Reply #64 on: August 12, 2020, 09:07:18 AM »
I can say from experience, many companies have a culture/policy of blaming the user for product failures to avoid recalling hundreds of thousands of them.  My father brother and i put in over 70 combined years at one very famous manufacturer and i had their product explode literally in my hands very painfully.  

We couldnt even get a replacement.  They always insist on you sending them back for "inspection" then send a canned response "evaluation" that it was your ammo or your fuel or your abuse, i knew the system and individuals well from the inside.  I was sometime the guy who crushed up the exploded guns, and i grew up with the guy who received them daily in the mail room.  Canned response guy was a lowlife dirtbag, that was his job.  Lie to defer blame.   They just want the evidence back so a 3rd party cant inspect it at a class action suit.  


What im saying is the dealers and the users will be a lot more honest with you then the manufacturers.  The dealers bread and butter is loyal nearby customers, not protecting the MFR.  The manufacture have a life and death (of their jobs) incentive to shift the blame to end user and denying fault, like the insurance industry.   Just keep it in mind, this is any mfr.  Im not hating on stihl corporate. 

Anyone who got caught being honest about this stuff online always got fired and yes the mfr's follow employee social media.

Revelation 3:20

Offline Old saw fixer

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Re: Stihl 261s Scoring Pistons
« Reply #65 on: August 12, 2020, 06:13:18 PM »
     This thread put a hitch in my step on my journey towards an MS261CM.  I've sorted out a few dealers to check with,  but none are real local.  Last week I went to the dermatologist (the sun isn't that good for you, lol) but after wearing a mask for about two hours I was done with it.  After the dermatologist I stopped by Costco and remembered I left the cold pak at home.
     I will check the dealers I was referred to on a later trip. 
     I will keep an eye on this thread, too.

Offline gspren

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Re: Stihl 261s Scoring Pistons
« Reply #66 on: August 12, 2020, 06:28:58 PM »
    This thread put a hitch in my step on my journey towards an MS261CM.  I've sorted out a few dealers to check with,  but none are real local.  Last week I went to the dermatologist (the sun isn't that good for you, lol) but after wearing a mask for about two hours I was done with it.  After the dermatologist I stopped by Costco and remembered I left the cold pak at home.
    I will check the dealers I was referred to on a later trip.  
    I will keep an eye on this thread, too.
There are quite a few of us on here that have 261s and this is the first I've heard of a problem and this one is being used differently than most so if your use is "normal" cutting I wouldn't be concerned.
Stihl 041, 044 & 261, JD 2355 4X4 w/fel, JD 620, Yamaha Kodiak 400 & trailer, Kubota 400 RTV,  P&M OWB, 75 acres to play.

Offline Spike60

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Re: Stihl 261s Scoring Pistons
« Reply #67 on: August 13, 2020, 06:39:31 AM »
This is exactly the problem that realzed was talking about above, and it's unfortunate. One guy has an issue with a particular model and people often adopt an unfounded "they all do it" fear about it. They shy away from buying one or begin wondering when their own saw is going to blow up. Like I said earlier, if there were any serious problems with 261's, it would be a well known fact here and on other saw sites.
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Offline realzed

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Re: Stihl 261s Scoring Pistons
« Reply #68 on: August 13, 2020, 06:56:51 AM »
AND Spike - long, long before now!

Offline Old saw fixer

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Re: Stihl 261s Scoring Pistons
« Reply #69 on: August 13, 2020, 04:02:35 PM »
     I don't have a fear that "they all do it".  I am trying to find a Stihl dealer I can depend on.  The price out the door isn't that important since as a new customer I am not apt to get a deal.  It's the skill level in the shop that is my biggest concern, especially with newer developments like the M-Tronic engine controls. 

     I can fix the darn saw, I have no doubt.  I have the mechanical aptitude and tools I need.  I just don't have access to the "technology" any more. 
 

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Re: Stihl 261s Scoring Pistons
« Reply #70 on: August 13, 2020, 07:08:40 PM »
So what do you do when you need to have a new car or truck?  
The situation is pretty much to a degree the same with any mechanical device these days - as in most everything you purchase doesn't give you much of any choice but to have to default to the manufacturer's specific repair depot for fixes or adjustments and that won't change to help any of the 'Mr. Fixits' going forward..
It's the way things are destined to go if you want anything with a warranty or new for the most part, that will be easy and trouble free operation without a lot of fiddling, like most all of the new vehicles we all drive and use daily now.
But its not just limited to cars or trucks - its appliances, or home related heating and cooling devices, and virtually everything else that is being driven by microprocessors and the latest electronic systems that you need to be an electronic genius to figure out - let alone troubleshoot and repair.
We all like the conveniences that go along with it when everything works well and when it serves us well, but hate it when we don't have things operating the way they should or the way we are accustomed to having them run!
Welcome to the new age!  

Offline Real1shepherd

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Re: Stihl 261s Scoring Pistons
« Reply #71 on: August 13, 2020, 08:01:22 PM »
So what do you do when you need to have a new car or truck?  
The situation is pretty much to a degree the same with any mechanical device these days - as in most everything you purchase doesn't give you much of any choice but to have to default to the manufacturer's specific repair depot for fixes or adjustments and that won't change to help any of the 'Mr. Fixits' going forward..
It's the way things are destined to go if you want anything with a warranty or new for the most part, that will be easy and trouble free operation without a lot of fiddling, like most all of the new vehicles we all drive and use daily now.
But its not just limited to cars or trucks - its appliances, or home related heating and cooling devices, and virtually everything else that is being driven by microprocessors and the latest electronic systems that you need to be an electronic genius to figure out - let alone troubleshoot and repair.
We all like the conveniences that go along with it when everything works well and when it serves us well, but hate it when we don't have things operating the way they should or the way we are accustomed to having them run!
Welcome to the new age!  
What you're looking for is longevity....at least similar to what were were used to once upon a time. That's the missing part. Companies have sold millennial's and gen z's that things only need to last five yrs......just out of warranty, it's OK if they die. They want to save the planet/eco system, yet they're forced into a throwaway mentality/society.

And if you're raised that way, you won't be trying to recycle old stuff by fixing everything. Let the millennial's and gen z's figure out how to hack the systems, so we can get in and repair the mechanical parts.

Kevin

Offline smoked

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Re: Stihl 261s Scoring Pistons
« Reply #72 on: August 16, 2020, 08:30:39 PM »
You know, reading this and watching that brushing video makes me wonder if that is what happened to my old 025.  Rand great for years but all of the sudden, had no power and could not tune it no mater what.  I did not check the piston or have a compression tester.  Carb rebuild did not help so I sold it for parts.  figured I got my $300 out of it anyway after 25+ years :) 

Anyway, the last time I remember it running right was when I was roughing out some bowls...which is very similar to that brushing process.  I ended up buying one of those scary angle grinder attachments that run a 1/4 in saw chain.  They get it done and are a little easier to handle as long is you keep the right part of the circle engaged.
Hobby woodworker/wood burner
If I screw something up, it is free heat next winter:-)

Offline Old saw fixer

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Re: Stihl 261s Scoring Pistons
« Reply #73 on: August 17, 2020, 04:38:52 PM »
     realzed, I don't buy new cars or trucks.  My truck is a 1992 GMC K1500, my beater car is a 2003 Subaru Forester.  I think I am basically butt hurt because now I am a customer, instead of the guy in the back fixing pro saws, and buying new ones at cost.  Such is life, lol.  I like taking care of my stuff myself.

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Re: Stihl 261s Scoring Pistons
« Reply #74 on: August 17, 2020, 07:15:01 PM »
    realzed, I don't buy new cars or trucks.  My truck is a 1992 GMC K1500, my beater car is a 2003 Subaru Forester.  I think I am basically butt hurt because now I am a customer, instead of the guy in the back fixing pro saws, and buying new ones at cost.  Such is life, lol.  I like taking care of my stuff myself.
At some point obviously you will be stuck with technology that you won't have the tools or expertise to deal with well - its just a fact of automotive life (and probably that of chainsaws and other small equipment as well).. Unfortunately then you will have to either have to adapt to it or go without the improvements and upgrades that 'often' comes with that technology in those same tools or vehicles..  Its the way the World is evolving (some say not).. like it or not!

Offline Real1shepherd

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Re: Stihl 261s Scoring Pistons
« Reply #75 on: August 18, 2020, 09:17:21 AM »
    realzed, I don't buy new cars or trucks.  My truck is a 1992 GMC K1500, my beater car is a 2003 Subaru Forester.  I think I am basically butt hurt because now I am a customer, instead of the guy in the back fixing pro saws, and buying new ones at cost.  Such is life, lol.  I like taking care of my stuff myself.
At some point obviously you will be stuck with technology that you won't have the tools or expertise to deal with well - its just a fact of automotive life (and probably that of chainsaws and other small equipment as well).. Unfortunately then you will have to either have to adapt to it or go without the improvements and upgrades that 'often' comes with that technology in those same tools or vehicles..  Its the way the World is evolving (some say not).. like it or not!
Or you can fix older stuff back to their prime and enjoy. I have enough old pro saws that I don't have to worry about failure on a job. So I take four "antique" saws to a job instead of two new ones....big deal. I only had one job ever where I had to go past the second saw and that was a fluke set of circumstances.

At some point you have to ask yourself; is the newer technology actually a better product and will it radically outperform my older stuff......

Kevin

Offline mike_belben

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Re: Stihl 261s Scoring Pistons
« Reply #76 on: August 18, 2020, 01:41:24 PM »
The more advanced the technology, the more important it is to have your ownership be near the beginning rather than the end of the product's life cycle. 
Revelation 3:20

Offline sawguy21

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Re: Stihl 261s Scoring Pistons
« Reply #77 on: August 18, 2020, 01:54:55 PM »
Kevin, I like the older saws too as I can keep them going with a minimum of tools and newfangled technology. Trouble is, you would likely not be hired by a major contractor if you showed up with your 2100 but I don't know how the system works in your area. Do the mills hire logging contractors that sub out the falling or is it a bunch of small independents?
old age and treachery will always overcome youth and enthusiasm

Offline Real1shepherd

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Re: Stihl 261s Scoring Pistons
« Reply #78 on: August 18, 2020, 07:03:37 PM »
Kevin, I like the older saws too as I can keep them going with a minimum of tools and newfangled technology. Trouble is, you would likely not be hired by a major contractor if you showed up with your 2100 but I don't know how the system works in your area. Do the mills hire logging contractors that sub out the falling or is it a bunch of small independents?
These days I get involved in private timber tracks or remove problem trees. So I would be an independent providing my own gear, insurance & bonding. But then it gets twitchy when I move over to the next state and do work. One big customer there puts me on his payroll for insurance purposes......but I can't bring any help with me.....weird, but I assume legal.

WA is a nightmare of bureaucracy....especially in the timber business. These days, I try to stay clear of all that.  It's been decades since I worked for any of the big timber houses.....I can't speak for what that's like anymore.

If you Google timber contractors in the State of WA you get hundreds and hundreds of outfits besides the big houses. But that's everyone big and small.

The mills do work with contractors and those guys do sub out falling. There used to be a lot more of it when the IRS tolerated contract labor. Pretty much now you have to be at least a small business or work for a co. 

Kevin

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Re: Stihl 261s Scoring Pistons
« Reply #79 on: August 19, 2020, 09:42:14 AM »
Something else that came to mind. 
I may be wrong.
But my theory is fresh air stratified engines run lean at lower speed and exhaust stratified engines run rich at lower speeds. By lower I mean below full throttle. 
461s run at low rpms have high carbon and oil deposits, while as the few  fresh air stratified engines seem to have whitish spark plugs even with 25:1 oil mix . Well my exposure to both types are very limited. The 461 is the only exhaust stratified we have here while as I have seen fresh air stratified Huskies the 575 and their XTorq brushcutters, the Sthil 211, all seemed to be leaner than the usual two strokes, while as the 461 seems the 'dirtiest'

Well, I may be wrong, but I thought I would drop this into the current pot to stir up  :D

Offline Greenhighlander

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Re: Stihl 261s Scoring Pistons
« Reply #80 on: August 23, 2020, 07:07:31 AM »
I can't comment on the half throttling other then to say it makes sense that 2 stroke engines are made to be wide open or idle not in between the two.   
I had a 261 with a scored piston and cylinder .  Was my first new saw that I had ever bought.  It lasted for roughly 20-30 cord .   After racking my brain on what could of caused it and certainly being no expert, I am convinced it was from running it completely out of gas each tank before refueling, while bucking up big yellow birch and sugar maple.  I did have it tested for  leaks that would of leaned it out and none were found. But running it dry each time sure made it lean out between the first sign of low fuel and actually running it dry. 

All that being said unless you are a small engine mechanic yourself the #1 thing when buying a saw in my opinion is dealer support. I have been using a 445 and an old 250 for my firewood since, but have now saved up enough for a new ms 261 and have found a dealer who isn't all sales. When they go on sale this fall I plan on buying an MS 261 C-M. 


"Companies have sold millennial's and gen z's that things only need to last five yrs......just out of warranty, it's OK if they die. They want to save the planet/eco system, yet they're forced into a throwaway mentality/society. "  

Just out of curiosity what age group do you think made it that way?   Pretty sure it wasn't millenials and gen Z running these companies.  

Offline Real1shepherd

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Re: Stihl 261s Scoring Pistons
« Reply #81 on: August 23, 2020, 09:36:13 AM »
Just out of curiosity what age group do you think made it that way?   Pretty sure it wasn't millenials and gen Z running these companies.  

I'm certainly not gonna defend the P.T. Barnum's of my generation. But ask yourself how it got to be this way, because that's not how I remember it growing up when you took pride in buying major appliances and power saws/lawn/garden equipment. You expected them to last and they did with some maintenance.

But you have corporations like Apple worth two trillion dollars run by a despot who made sure your primary electronic devices were dated/throwaway after a few yrs. Same with Microsoft....who doesn't remember the push to buy or update your PC every few yrs?

All that trickled down along with price point Asian made goods....people demanded value above all and instant gratification without saving for anything.....and so here we are.

Millennial's and gen Z's aren't the monsters here, but they sure are the automatons.

Kevin

Offline Spike60

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Re: Stihl 261s Scoring Pistons
« Reply #82 on: August 26, 2020, 05:52:01 AM »
Running a saw dry every time does essentially create a temporary air leak. Once that fuel filter is sucking in as much air as fuel it's little different than a hole in the fuel line, tear in the intake boot, etc. It can generate a failure code in an AT saw. IMO, doing this can be worse in the AT and CM saws as the carb will adjust the fuel settings and dump more fuel into the saw to compensate and try and keep the RPM's up. In this way it sort of prolongs lean running where an older saw will stall out quicker. Not only that, but when you fuel up the saw and go back to work the fuel settings are now out of whack and it needs some time to re-adjust itself.
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Offline Greenhighlander

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Re: Stihl 261s Scoring Pistons
« Reply #83 on: August 26, 2020, 06:06:40 AM »
Running a saw dry every time does essentially create a temporary air leak. Once that fuel filter is sucking in as much air as fuel it's little different than a hole in the fuel line, tear in the intake boot, etc. It can generate a failure code in an AT saw. IMO, doing this can be worse in the AT and CM saws as the carb will adjust the fuel settings and dump more fuel into the saw to compensate and try and keep the RPM's up. In this way it sort of prolongs lean running where an older saw will stall out quicker. Not only that, but when you fuel up the saw and go back to work the fuel settings are now out of whack and it needs some time to re-adjust itself.
Ya it really wasn't one of my finest hours. The worst thing is is that I did know better but somehow forgot. I seem to need to learn things the hard way sometimes . But hey that way I don't forget haha 
 I never go past the first sign of low fuel since and usually refuel even before that. 
I still have the saw and am hoping a fair amount of the parts may be usable on the new 261 CM .  


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