Muffler Modding an MS361

[JohnG28]

At the request of one of our fellow members, Matt aka Piston, I am posting the procedure that I used to mod the muffler on my 361.  This could be used on a variety of saws as well, with some slight changes depending on the saw.  I'm sure others have advice to add as well, especially since I learned this from the forum myself. ;D Thanks to Kevin, aka Cut4fun, Bill Gaiche and anyone else who helped me along for their info when I did mine.  I'm including removing the limit caps on the carb as part of the process, as it is a must to be able to tune your saw once mods have been made.

Starting with the air filter cover removed you need to get to the limit caps on the H and L needles.

 
Remove the 2 hex nuts under the filter to get the air box off, which will give you access to the boot covering the adjustment screws.

 
Pulling the carb out a little on its mounting bolts will give you the room needed to pry off the boot, but be carful not to damage it!

 
Now you have access to the limit caps on the carb.


 
The limit caps are the red plastic pieces seen in the photo.


 
Note the grooves at around 5 o'clock in each, these grooves are how the caps go in to the carb body.  Turning both the H and L out (counterclockwise) as far as they will go will align a tab on each of the red caps with the groove in the carb body.  Once aligned, the caps can then be pulled out of the carb body.  I have heard of using a drywall screw to screw in to the caps and pull, however I got them out using a screwdriver and needle nose pliers.  When you get each out, there is a tab on each which simply needs to be trimmed off with a utility knife.  After trimming, they go back in, which will help keep the carb screws from vibrating out of later on.  You now have a fully adjustable carb! 8) Put everything back together on the carb side of the saw and then off to the exhaust side.
Now for the muffler.  I did my mod to on the recoil side of the saw as the factory exhaust is on the clutch side and there is more room. I started by drilling 2 3/8" holes.  I don't recall exactly but I left somewhere around 1/4" between them.


 
Initially I had only used these 2 hoes as my mod and had good results, but later I went back with a Dremel and a milling bit and cut out the material between the holes, then a grinding bit to clean up the edges.

 
Next I used a Husky 288 deflector and 288 spark screen, Bailey's part #s HVP 503 58 99 01 and HVP 503 40 56 01, respectively.  Also used a pair of sheet metal screw to attach. The screen isn't necessary, and can be omitted if you choose.

 
I drilled pilot holes for the self tapping screws and then drove them in put the screen and deflector over the new exhaust port.  Reattach the muffler, making sure to put the heat shield and gasket back on as well. Here it is all done. ;D ;D

  

 

Once back together you will need to return the carb to account to the changes, which will include opening up the H for sure and probably some with the L and idle as well.  I like Madsen's site for info on tuning, which even has audio files so you can hear a saw from lean to rich.
http://madsens1.com/saw_carb_tune.htm

All in all, the saw runs better, cooler, and has more torque and power.  Years later and it still looks great inside looking through the exhaust port.

  

 
May be hard to see in the photos, but there is a nice film of oil clearly visible on the piston.  I keep mine set on the rich side, and have had no problems doing so at all.

Hope this helps out Matt, and feel free to ask if you or anyone else has questions.  Happy sawing! ;D

[Piston]

Hope this helps out Matt, and feel free to ask if you or anyone else has questions.  Happy sawing! ;D

WOW!  You went above and beyond John!  Thank you for taking the time to post the process.  The pictures and instructions will definitely come in handy, and your explanation actually makes it sound very easy.  I may have an issue with tuning the carb as I've never done that, but I guess I'll cross that bridge when I come to it.   ;D

So, my first question is, does it matter a whole lot what the size of the eventual "hole in the muffler" is?  Since the carb will be adjusted after the fact, will tuning the carb account for any variables in the muffler hole size?  As long as I try to drill the same size holes, in similar locations, and cut them out the way you did, I should be good?  Or does it have to be "exact"? 

I'll order the parts from Bailey's tonight.  ;D  Thanks again, I'm sure this will be very useful for myself, as well as many others.  8) 8) 8)

-Matt

[JohnG28]

No problem at all, sir.  I recall from others the most you would want to open it up is roughly 80% of the size of the cylinder exhaust port. I started smaller, as you can always make it bigger later, but not smaller. Glad to help you out.  Look forward to seeing your progress now!  ;D

[beenthere]

JohnG
Thank you for those pics and explanation.

I've often wondered just what was up with the discussions of the limiter caps and just what they were all about, as well as the muffler mods. Tempting to do that to my MS361 but it gets the job done well now, so always hesitated making any mods. Much more tempting now with the good tutorial.

Bothered me a bit seeing the sawdust around the carb when it was apart, and wondered if blowing it off before removing the filter would be good, or may just be a risk of causing a different problem.

Would be great info to have in our database under "Muffler Mod" and "limiter caps", IMO

[clww]

Very informative post! 8) 8) 8)
I am now inclined to perform this mod on my 361.

My only question is how is the noise, compared to stock?

[JohnG28]

Beenthere, I thought the same about the saw dust, only I already had it apart when it occurred to me.  : I should have blown it off first. I did have the choke closed though. It does run noticeably cooler, especially in the summer cutting, so it is worth while IMO.  Again, glad to help. How would I go about getting this into the database, or is this something an administrator needs to do?

[JohnG28]

Very informative post! 8) 8) 8)
I am now inclined to perform this mod on my 361.

My only question is how is the noise, compared to stock?

It does make it louder, but not all that much I don't think. I really can't recall how it sounded before it's been so long now.  :D

[chadihman]

Looks good! I open the 361 muffler by cutting it at the seam then I gut everything inside weld it back together and add a pipe cut at an angle pointing forward on the starter side. I cant remember 100% what it looked like inside but I know it was  the most chocked up muffler I had ever seen and I decided it all had to come out to make a big difference. It made a really nice gain on mine

[Piston]

Glad to help you out.  Look forward to seeing your progress now!  ;D

I'll be sure to let you know once I get around to it. I'm hoping that I'll get a chance to do this next week.

[Piston]

Next I used a Husky 288 deflector and 288 spark screen, Bailey's part #s HVP 503 58 99 01 and HVP 503 40 56 01

I just ordered these parts from Bailey's.  ;D

[JohnG28]

Good deal, easy afternoon project for sure.  ;D One thing I forgot to mention that you should also do is get a shop vac and suck out the muffler after drilling, cutting, grinding etc. Don't want any metal in there that could find its way back into the engine. And study that Madsen's link, particularly the sound link. That was the best way I understood tuning by ear and never used a tach.

[gspren]

  Would a 261 mod be about the same?

[JohnG28]

I don't know a lot about the 261, it's a strato saw I believe.  I think you would still see a gain but I don't know how much.  Anyone done one before on a 261?  Also, if it has a cat muffler I don't think you'll want to be cutting into that stuff, nasty crap.

[john_bud]

MS261 muffler mod that I did.  Internally opened up a bit,  Opened the exit a bit and added a 2nd opening with angled slits. 



  



 



 


If I could do it over, I would cut the slits  and then angle them one at a time.  That would be easier to get them angled strongly forward.  Heck,  I may go back and cut the slits off and add a deflector / screen.   The mod may not be as open as it needs to be for max benefit as it is.   Live and learn...

  Would a 261 mod be about the same?

[img width=550 --Photos MUST be in the Forestry Forum gallery!!!!!--.com/albums/c201/john_bud/20130825_131902_zps1d584292.jpg[/img]

Too hard to add pic on my smarty phone.  Will try to add them later on a real puter

[Ward Barnes]

JohnG:

I have a new (this week) MS 362.  Would a muffler mod be something that I should consider?  So far this saw is a dream come true.

God Bless, Ward and Mary.

[beenthere]

Ward
Have had my MS361 for 9+ years, and I'm still too satisfied with its performance and too chicken to mess with it, although the muffler mod is sure tempting. I don't find any shortcomings in the MS361 with 20" bar when the chain is freshly sharpened. Drops right through the oaks, hickory, and ash that I mainly cut for firewood.

Maybe get more hours under your belt with this dream saw, and the newness will wear off and you will get bored with its performance and want more. Then do the mod...   ;D

I'm still in the dream, and can't believe it has been almost 10 years since new.

[JohnG28]

John_bud, thanks for the input on the 261. What kind of improvement have you seen?
Ward, if you just bought this saw I wouldn't mess with it until the warranty expires. You will void the warranty for sure if you make modifications.

[bandmiller2]

Thanks John, you made it very clear. I always used your plan "B" the drywall screw to remove the caps by grinding the point flat, it pops them off easily undamaged. Frank C.

[john_bud]

John_bud, thanks for the input on the 261. What kind of improvement have you seen?
Ward, if you just bought this saw I wouldn't mess with it until the warranty expires. You will void the warranty for sure if you make modifications.

Not a night to day change, but better.    I think I could open it up a bit more as I was fairly reserved.  Anyhow,  it cuts big oak with a 20" bar nicely.  It was struggling a bit prior.  Basically, the "struggle" went way down.   It's hard to honestly quantify w/o a dyno, but it feels like it has more torque to keep pulling.  It is worth the time spent, imo.

[Ward Barnes]

Beenthere and JohnG:

Thanks for the input on porting the 362.  When we purchased the saw we also purchased a 6-pack of Stihl synthetic oil.  Stihl has a program where when you purchase a new saw or weedeater and buy the synthetic oil Stihl doubles the warranty .  On our new weedeater it went from a 2 year to a 4 year and on the 362 from an one year to a two year warranty so any muffler mod is at least 2 years away.

Earlier I stated that the dealer swapped the 20 inch bar for a 24 inch.  I'm glad I looked before ordering a couple of new chains from Bailey's as the bar is a 25 inch and uses a 84 link chain.  Bailey's is currently running a special on the WoodlandPRO chains where you get a 6.4 ounce bottle of their synthetic 2-cycle oil with each chain purchased.  That plus the 12 bottles purchased when we purchased the weedeater and saw should keep me cutting for some time.  We use 92 octane non-ethanol fuel from a local marina and the saw and weedeater love it.    8)

[Icehouse]

JohnG really like your 361 mod, hardware is easy to come by. My second 361 mod I did was from a kit I found a guy selling on eBay, think they still are selling them. Just about the same as yours, parts are a little cheaper. My first 361 mod was a mod developed by a gentleman in n California. He went by Lakeside53 on AS haven't seen him on there for awhile. His mod is by far more complicated than yours but works well. Thanks for posting, I love all my 361's, the muffler mod really wakes them up, strongly recommend folks doing it.

[JohnG28]

Thank you, sir. I like it, works well and like you said, wakes it up a bit. I like that it looks like it came that way, hard to notice it's not from the factory IMO.

[tomjv]

Hey Guys, I have two MS361s!   I want to mod them both.  I like this page/mod.  I have a question.  The original post shows work done on the carb, pretty much all on the outside.  Then later on, another guy explains how he "gutted" his unit.  Which is it? 
Should I remove the carb and do the port or  try to split the unit and gut it?
Also, anyone try pop-rivets on the shield?

Thanks in Advance,
TomJV

Sorry about resurrecting an old post, but this one was REALLY to the point and I could see the point in starting another and trying to reference it.