Ms 260 muffler mod template

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Hi guys,


With some help from a few great guys on here I have modded the muffler (still need to spray the exhaust and shroud black and rivet the shroud on)

what I found so difficult was fitting the shroud between the exhaust and crank case whilst avoiding the chain brake.


I was banging my head against the wall for days trying to bend the Aluminum and get the shape I wanted and to fit so I have added a template below which may help you guys out!

You’ll need:

aluminum sheet 0.5mm thick.
3.2mm x 1.6mm aluminum rivet
Spray paint to avoid galvanic corrosion
16mm Drill bit it dremel.

I firstly removed the baffle which was harder than I thought, not wanting to drill the spot weld out incase I went all the way though (as I don’t have a welder to repair it) I used pliers, cutting disk and grinding wheel to remove it.
1373DAB9-C771-4E59-AFAD-CA4F68188785.jpeg
38FD1EAC-2137-4AAD-B74B-350A2F00A70D.jpeg

I then I flattened the original exhaust flaps, centre punched a hole and drilled them away.

Ignore that this was a 20mm drill (will use that when I enter the realm of porting)
View attachment 786826 46027A18-03B8-41EA-8561-A6C02789AB51.jpeg


After much messing around with paper and cardboard templates I got a shroud fitted

8E6893D2-1332-48F6-A5F0-D2AA5FD15787.jpeg 6F07317F-2325-4FFF-AF04-E975EED87375.jpeg 7C38B346-A341-46CD-941E-CD6B21624334.jpeg 5C7A4770-4A7F-47CC-89B1-3C1B9045F700.jpeg 4F54758C-7552-4D54-B909-4DC8AB0ACF83.jpeg


I big thank you to @drf255 and @pioneerguy600 who have helped me with the project sharing tips tricks and advice. It’s so much appreciated guys, thank you.
 
Never seen a 260 muffler that looked like that! I think that you could have saved yourself a LOT of grinding by just getting a used rear part of the can from a USA saw which has NO baffles. Take a look on Ebay for used mufflers and photos thereof. I usually just drill out the area behind the screen on USA mufflers. This mimics the original early 026 mufflers before the EPA got involved.

That almost looks like an aftermarket muffler. Did either section have any Stihl part numbers on it? All of the OEM ones that I have seen do.

I think that I can see a TIG welder in your future!
 
Never seen a 260 muffler that looked like that! I think that you could have saved yourself a LOT of grinding by just getting a used rear part of the can from a USA saw which has NO baffles. Take a look on Ebay for used mufflers and photos thereof. I usually just drill out the area behind the screen on USA mufflers. This mimics the original early 026 mufflers before the EPA got involved.

That almost looks like an aftermarket muffler. Did either section have any Stihl part numbers on it? All of the OEM ones that I have seen do.

I think that I can see a TIG welder in your future!
Hi :)
It’s OEM, as pioneerguy said it’s European without spark arrester. I was warned against putting holes in the front cover because they are much louder and also something about losing pressure and thus power? Don’t quote me, my memory isn’t the best!
 
Hi :)
It’s OEM, as pioneerguy said it’s European without spark arrester. I was warned against putting holes in the front cover because they are much louder and also something about losing pressure and thus power? Don’t quote me, my memory isn’t the best!
The noise is based largely on the outlet size. The deflector you made might actually be noiser because it directs the exhaust and resulting sound waves against the log your cutting.
Pressure isn't function of outlet size as well.
 
The noise is based largely on the outlet size. The deflector you made might actually be noiser because it directs the exhaust and resulting sound waves against the log your cutting.
Pressure isn't function of outlet size as well.
Ah okk, as I say I have no clue here and no experience. I’m just following designs shared by those with way more experienced Than I :)
 
Many first time muffler modders really make a dogs breakfast of it. Nice to see you took your time, got advice & did a good decent job. Credit where credits due.
Wow thank you! Yes first time :) did lots of research, got some great advice as you said and got really annoyed not being able to get it all set correctly and bent nicely. Kept going back to the drawing board and finally got there :)
 
I see you're using the mesh that is one step coarser than stock. This cuts the flow restriction considerably and is the mesh I use. Just wondering, did you measure the area of the rectangular exit? The exhaust exit area will be the smaller of this and the round hole.
Hey! I’m not sure about the size of mesh, I figured they would be all fairly similar. Why have you chosen to use a finer mesh than standard? Just got a 260 screen on order to see the difference :) it’s only 6 dollars so worth my interest to find out!

The front exit is smaller, but it can exit out of the top of the shroud too, it’s not a closed area. This was one of the reasons I left the 90 degree angle there.
 
From what I can see in your picture, the mesh you and I are using is coarser than stock, not finer. The stock mesh cuts flow significantly, the coarser mesh not so much. I don't remember the size number of the mesh I bought, it looks like yours. Also, I see now that the outlet shroud is open. As Roseann Rosannadanna would say...Nevermind.
 
The mesh is from an ms 180 which id imagine won’t let as much air through as the ms 260 mesh. Imll get back to you when it turns up :)

I think that Stihl uses the same mesh in all its saws, at least in the U.S. market. I have not noticed any differences across any of the Stihl products that I have rebuilt / worked on. I suspect that it may be OSHA or USFS requirements based.
 
From the USDA Forest Service:
"Screen-Type Spark Arresters as defined by USDA Forest Service Standard 5100-lb fall into a special category. They are intended for use on small engine applications. All exhaust products must pass through the screen, which has openings of 0.023-inch or less. the effective exhaust area of the screen (total area of all screen openings) shall not be less than 200 percent of the engine exhaust port area at its smallest cross-section. Screen material shall be heat and corrosion resistant, and shall provide at least 100 hours of service life"
 
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