# MS261C -M Muffler Mod ?



## Dilier23 (May 3, 2015)

Good evening. Looking into doing a muffler modification on my MS261C-M but haven't seen any that have louvers cut into the front of the muffler where there are groves pressed in already. Is there something behind the front of the muffler that would make it not a good idea to cut into ? 

For some reassurance, the M-Tronic will adjust air fuel mixtures to compensate for additional flow?


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## pantelis (May 3, 2015)

After some holes in my saw muffler the saw have power like






for some reasons the factory dont know how to do it , or dont have the correct tools so i decide to do it my self and the results are more than perfect




so take yours grandfather 100 years old drill and start drilling .


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## dwraisor (May 3, 2015)

Hit up the search, enter *ms261 muffler mod *and you will see several pages of results but the first page will be plenty, surely lots of pics and examples....

Yes the Mtronic will adjust, you may have to follow the reset (again teh search box is your friend). Most newer Stihl muffs are just empty cans... (ones I have seen) but putting outlets on the front, *CAN* lead to catching the tree you are cutting on fire. Maybe less likly on a 261, ans you probably would never have it in a tree big enough that the muffler has time to ignite the bark.


dw


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## Dilier23 (May 4, 2015)

I went ahead and tried it out. If it was done again I would not have cut the lower slot, the upper would have been enough extra in my opinion. It is louder, I don't particularly like that. The additional power is noticeable. I had been running an 18in bar, put a 20in on after the muffler mod and it will pull the longer bar better than a stock saw with an 18in bar. I made sure to reset the M-Tronic in a large enough log to use the entire length of the bar.


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## blsnelling (May 4, 2015)

You can't make it flow freer and not be louder.


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## blsnelling (May 4, 2015)

Here's a 241, very similar to the 261. This will shoot the exhaust off to the side...much less likely to catch the bark on fire.


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## wyk (May 5, 2015)

Removing the baffle from the 261cm makes the most difference I have ever seen a muffler mod do on a stock saw - about 25-30% better cut times. I often do not port 261cm's that come to me any more. I simply muff mod them for half the price.


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## rumatt (Jun 16, 2018)

Bumping this thread to hopefully get more thoughts on muffler modding 261's (and 241's)

Searching is producing lots of discussion about how well it works, but very little detail on how to make the mods.

Are there any how-to guides on how to diy the removal of the spark arrestor screen? Any recommend folks who do this for a fee?


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## wyk (Jun 17, 2018)

rumatt said:


> Bumping this thread to hopefully get more thoughts on muffler modding 261's (and 241's)
> 
> Searching is producing lots of discussion about how well it works, but very little detail on how to make the mods.
> 
> Are there any how-to guides on how to diy the removal of the spark arrestor screen? Any recommend folks who do this for a fee?



The 261cm is a great little saw. With a bit of work, you can get some impressive gains simply modifying the muffler.

The 261 is different from most of it's brethren in that it has a baffle plate situated directly between the cylinder exhaust exit and the muffler exhaust exit. It is the ONLY thing in the muffler that prevents the exhaust venting nearly directly from the cylinder in to the world. One. Tiny. Plate. When you remove this, the exhaust now has about an inch of travel before it hits atmo. This does two things - removes and prevents any chance of exhaust reversion - and it makes the exhaust very, very, very loud. The end results are much more power everywhere in the rev range.

This is what the muffler should look like when you remove the baffle(I've also opened the external muffler port a bit) - you should be able to see the cylinder exhaust port directly from the outside of the muffler:






This is the result I get on video - the unmodified 261 first, and then only a muffler mod:


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## rumatt (Jun 17, 2018)

Thanks reindeer. I'm googling "261 baffle" to see what I can find for a diy. 

It seems the stainless steel muffler is tricky to work with. I'm also concerned about how loud "very loud" is. I wear ear protection but I do have neighbors.

Is there an in between solution? Something like what. Mastermind posted at the end of this thread 

https://www.arboristsite.com/community/threads/who-does-the-fancy-stihl-ms261-mm.230800


> The easy way to do a 261 muffler is by cutting a slot under the factory opening.....yet still inside the deflector. That's how we do the 441, 362, and 261....



Would this allow me to start with small openings to judge the volume, and proceed as I feel comfortable?


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## wyk (Jun 17, 2018)

I've never done a different mod, so I couldn't tell you how it works on the 261. What I CAN tell you about the sound is that the video camera and the wood is in the exact same place in both parts of the video, about 5 meters apart. And if you listen, it sounds nearly twice as loud in the second part.


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## blsnelling (Jun 17, 2018)

rumatt said:


> Bumping this thread to hopefully get more thoughts on muffler modding 261's (and 241's)
> 
> Searching is producing lots of discussion about how well it works, but very little detail on how to make the mods.
> 
> Are there any how-to guides on how to diy the removal of the spark arrestor screen? Any recommend folks who do this for a fee?


The screen is removed with a single screw.


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## rumatt (Jun 21, 2018)

blsnelling said:


> The screen is removed with a single screw.


Sorry, I meant removing the baffle plate, as reindeer described.

Do you have a feel for how the following compare?

1. Side gills
2. Baffle plate removal (reindeer style)
3. Porting


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## blsnelling (Jun 21, 2018)

I have never felt the need to remove the baffle. It does not restrict flow through the gills I use exclusively.


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## rumatt (Jun 21, 2018)

blsnelling said:


> I have never felt the need to remove the baffle. It does not restrict flow through the gills I use exclusively.


Thanks!

It seems the 261c responds well to timing advances so I want to give it a try. Any tips on how much to try first?


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## SAWMIKAZE (Jun 21, 2018)

The new 261c muffler I just had in my hands didn't even have a baffle/tube.


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## Gypo Logger (Dec 14, 2019)

After running about 100 tanks thru 3 261’s, I’m anxious to try Brads method of muffler mod.
Is it just a matter of using a small cutoff wheel and cocking the louvers out with a bar wrench?
Or on second thought a 1” chisel blade?


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## SuperDuty04 (Dec 14, 2019)

Gypo Logger said:


> After running about 100 tanks thru 3 261’s, I’m anxious to try Brads method of muffler mod.
> Is it just a matter of using a small cutoff wheel and cocking the louvers out with a bar wrench?
> Or on second thought a 1” chisel blade?


That's exactly how I did my 261 MM. Night and day difference.


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## farmer steve (Dec 14, 2019)

SuperDuty04 said:


> That's exactly how I did my 261 MM. Night and day difference.


PICS!!


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## SuperDuty04 (Dec 14, 2019)

I'll have to get some later today when I'm down at my shop.


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## Gypo Logger (Dec 14, 2019)

SuperDuty04 said:


> That's exactly how I did my 261 MM. Night and day difference.


I actually changed my method of muff mod after one member pointed out the direction of the exhaust.
So I just elongated the existing port and port matched the gasket with the muffler and cylinder. I haven’t run it yet but will report back later today with results.
And I don’t want to hear any hoof rasp comments from the cheap seats! Lol


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## Gypo Logger (Dec 14, 2019)

A better picture of my fine workmanship.


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## pioneerguy600 (Dec 14, 2019)

Gypo Logger said:


> View attachment 779980
> A better picture of my fine workmanship.


 How about cold chisels and bfh`s?


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## Gypo Logger (Dec 14, 2019)

pioneerguy600 said:


> How about cold chisels and bfh`s?


I lent those to Al Smith.
I’m sure I got a 20% gain on the muff mod.


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## pioneerguy600 (Dec 14, 2019)

You going to replace the deflector?


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## Gypo Logger (Dec 14, 2019)

pioneerguy600 said:


> You going to replace the deflector?


No, I can’t see the point, I just elongated it. I went further on the second saw and ground away the rectangular box that the spark arrestor fits in.
I’ll take a picture.


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## pioneerguy600 (Dec 14, 2019)

As long as the hot exhaust gasses don`t melt anything then no need.


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## Gypo Logger (Dec 14, 2019)

The spark arrestor retaining bolt is a good delete because it strips easily.
I wonder it other muff mod maniacs also ground away where the bolt should be?


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## pioneerguy600 (Dec 14, 2019)

3/4" diameter hole is all they need.


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## Gypo Logger (Dec 14, 2019)

pioneerguy600 said:


> As long as the hot exhaust gasses don`t melt anything then no need.


Good thought Jerry, the exhaust will interfere with the chain break only if I run the saw with it on.


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## pioneerguy600 (Dec 14, 2019)

Don`t melt the handle, they melt easily, that is why I always use a deflector.


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## pioneerguy600 (Dec 14, 2019)

You know clicking it on and off with the engine running it will be right in front of the exhaust port. clickers!


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## MountainHigh (Dec 15, 2019)

Once I'm sure my saw is running rock solid, I'll be doing a muff mod but I want/need to retain the spark screen. 
Any suggestions on best way to open it up and still only use the spark screen outlet?


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## pioneerguy600 (Dec 15, 2019)

Maybe John can help you, I always toss the screens away, no need for them here.


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## MountainHigh (Dec 16, 2019)

pioneerguy600 said:


> Maybe John can help you, I always toss the screens away, no need for them here.


John? 

I'll pull my muffler off over the holidays and have a peek at what might work.

Thanks and Merry Christmas.


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## pioneerguy600 (Dec 16, 2019)

MountainHigh said:


> John?
> 
> I'll pull my muffler off over the holidays and have a peek at what might work.
> 
> Thanks and Merry Christmas.


 Gypo Logger.


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## split_wood (Jan 6, 2020)

noob here. Any more info? Thank you.


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## EchoRomeoCharlie (Jan 6, 2020)

split_wood said:


> noob here. Any more info? Thank you.


Cut a few slits down the flywheel side of the muffler with a dremel cut off wheel.

Bend the metal out to direct the gasses forward(bar side), if it's an M-tronic saw, re calibrate, and run it.


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## split_wood (Jan 23, 2020)

EchoRomeoCharlie said:


> Cut a few slits down the flywheel side of the muffler with a dremel cut off wheel.
> 
> Bend the metal out to direct the gasses forward(bar side), if it's an M-tronic saw, re calibrate, and run it.



I like that will give it a try.


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