# Please critique my muffler mod (MS290)



## Positrack (Jan 14, 2010)

Okay, here's the deal... I wanted to open up the muff while keeping the saw as quiet as possible. The way I did it was to open up as much area as I could outside of the baffle so the exhaust would still have to go through the baffle; it just wouldn't have to squeeze through the two absurdly tiny holes to get out. I did grind down the baffle a bit and bent in the recessed area so the exhaust has a straighter shot at the outlet, and I contoured (fancy word for "bent") the lip to make the opening sort of "3D" if you see what I mean. It is a pretty big opening. I also opened up the deflector a bit. My main concern is the baffle becoming the new restriction. I counted 22 1/4" holes in the baffle (11 per side) which ought to flow quite a bit, but I imagine my mod is still more restrictive than the "straight through the depression" mods I've seen most guys do since the exhaust must still go through the baffle. What do you guys think? Am I leaving a lot on the table by not "straight piping" through the depression or do you think the baffle will flow well enough? Any feedback/recommendations would be appreciated.

I ran it and tuned the low speed, but haven't had a chance to tune the high speed yet (I finished late. My neighbors are good and I'd like to keep 'em that way...). It really didn't seem too much louder than stock, but it sounded WAY better and badder. Me likes! I'll have to get it tuned and do some cutting with it and see if it helped.


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## nmurph (Jan 14, 2010)

i like it.....the color looks like something from a spaceship.....you need to paint the nuts to match!!!! a MM on that series will really change its attitude.


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## wigglesworth (Jan 14, 2010)

If that is what I think it is, a sandblast bare finish, It wont be long till that pretty muffler is a rusty muffler. But as for the mod, it looks good.


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## Positrack (Jan 14, 2010)

wigglesworth said:


> If that is what I think it is, a sandblast bare finish, It wont be long till that pretty muffler is a rusty muffler. But as for the mod, it looks good.



Ha! You're right, it sure does look sandblasted. I hadn't thought about it. It isn't though; it's silver header paint. It was the only high-temp stuff I had in the shop so that's what I used. I've had good luck with it. If cured properly, it lasts well.



nmurph said:


> i like it.....the color looks like something from a spaceship.....you need to paint the nuts to match!!!! a MM on that series will really change its attitude.



I wasn't sure about the color when I got it together, but it's growing on me. Anyway, I'll tune it up today, do some cutting, and see what I've got. It sure can't hurt; I can't believe the little tiny holes they expect this thing to breathe through. Poor saw probably felt like this ---> :taped: Makes you wonder why they do what they do...


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## CutaLot (Jan 14, 2010)

Looks good! Make sure you let us know how it runs, after a full test.


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## albert (Jan 14, 2010)

I did a few almost just like yours. You will be amazed how much power you will pick up. Looks nice


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## timberwolf (Jan 14, 2010)

You still have the internal restriction from the basket though.

IMHO it is better to cut the extra outlet in the dimple, that way the basket gets bypassed.


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## albert (Jan 14, 2010)

That's true but i think it may make the saw a good bit louder. The mod that in the pics does make the saw really perform pretty good. the ones I did were still 4 stroking pretty good @ 13,800, I don,t know if running that series saw much higher would be wise.


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## timberwolf (Jan 14, 2010)

If you are worried about how loud the saw is then yes keep the muffler mods in check, should be wearing hearing protection anyway right?

Look at the saws from 20 years back and they don't have a lot of the junk in the mufflers they do today.


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## albert (Jan 14, 2010)

You are 100% corect. The stock opening in a joke and really limits the power. His mod will give a very nice boost witout excessive noise.


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## Positrack (Jan 15, 2010)

I had the saw out today, and got it tuned more or less. I didn't have much to cut, but I noodled up some big oak rounds I had sitting waiting to be split. It definitely seemed to have more pulling power and didn't get bogged down near as easily. I could put way more pressure on it before it bogged down and it was puking noodles like crazy. It also seemed to rev higher at WOT, though I don't have a tach, just going by ear. It could have just been the different tone to the exhaust, but I don't think so. Is that normal with a MM? I'm pretty sure I don't have it set too lean (if anything, I tried to err on the rich side). I've got the high screw about 2 turns out from seated and it seems maybe a little rich; does that sound reasonable? It was pretty clearly 4-stroking at WOT but cleaned up when cutting. If I turn it out any farther, it seems to load up and wants to bog for a second when dropped back to idle so I figured that was too rich.

It's not too loud either, but it sure does sound better. Maybe I should have drilled the depression; I was just afraid it would raise the dead. I wear hearing protection, but I also occasionally use the saw in town trimming my mom's trees so I wanted it to stay semi-reasonable. I might think about maybe drilling a couple small holes in the lower part of the depression but I want to do some more cutting and make sure it's really tuned right before I make anymore changes. Overall though, I'm real happy with it. :chainsawguy: 
Thanks everybody for the input.


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## Echo6 Sierra (Jan 15, 2010)

Looks good! Being that you sand blasted it I hope you blew it out nice and good with an air compresseor before you put it back on and fired it up.

Sand and metal shavings are not good things to have in your cylinder....


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## albert (Jan 15, 2010)

Keep going leaner so it 4 strokes no load and cleans up as soon as put in in wood. Better to er on the rich side. I think 2 turns out on the H is too much if everything else is right. I recall the ones i did were no more than 1.3 turns out. I think your going to be around 14K rpm


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## NWnewguy (Jan 15, 2010)

*I think it looks pretty good*

The thing that I noticed the most was how much saw dust was built up on that 290. That was the only thing I could really say is wrong with them, until you go to rebuild one. They really are saw dust magnets though.


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## nmurph (Jan 15, 2010)

Echo6 Sierra said:


> Looks good! Being that you sand blasted it I hope you blew it out nice and good with an air compresseor before you put it back on and fired it up.
> 
> Sand and metal shavings are not good things to have in your cylinder....



he didn't sandblast it.


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## isaaccarlson (Jan 15, 2010)

*nice job*

but remember the lower part of your cutout is still covered up by the cover.....I am not sure where the trade-off is between noise and power because I went straight for the lakerized look on my 390.... CRAZY LOUD!!!! It was easy and looks good IMO. I just want to get a screen on it.


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## Positrack (Jan 15, 2010)

Echo6 Sierra said:


> Looks good! Being that you sand blasted it I hope you blew it out nice and good with an air compresseor before you put it back on and fired it up.
> 
> Sand and metal shavings are not good things to have in your cylinder....




I didn't sandblast it. I just painted over the factory bluing with header paint. The areas where you see bare metal were done with the wire wheel. I did blow and vacuum it out very thoroughly after a solvent bath though. It was full of shavings after I finished the hole.




albert said:


> Keep going leaner so it 4 strokes no load and cleans up as soon as put in in wood. Better to er on the rich side. I think 2 turns out on the H is too much if everything else is right. I recall the ones i did were no more than 1.3 turns out. I think your going to be around 14K rpm



I'm pretty sure you're right; it's too rich, but I'm new to saw tuning and wanted to make sure it wasn't lean. I'll lean it out some and see what she does. As long as it 4-strokes WOT no load, I'm rich enough right?




NWnewguy said:


> The thing that I noticed the most was how much saw dust was built up on that 290. That was the only thing I could really say is wrong with them, until you go to rebuild one. They really are saw dust magnets though.



Could be but mine was well past due for a good cleaning anyway. They do seem to pick up and hold a lot of crap though. I keep the chain sharp, but what little fine dust there is seems to accumulate where you see it in the photo. I cleaned it all out with the blowgun before I took it out for tuning.


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## Positrack (Jan 15, 2010)

nmurph said:


> he didn't sandblast it.



Beat me to it. 




isaaccarlson said:


> but remember the lower part of your cutout is still covered up by the cover.....I am not sure where the trade-off is between noise and power because I went straight for the lakerized look on my 390.... CRAZY LOUD!!!! It was easy and looks good IMO. I just want to get a screen on it.



I was afraid I'd cover up the cut out with the deflector so I actually painted it with a paint pen to match mark it and the deflector really doesn't cover the hole. Maaaaybe a tiny bit on the lower edge but not much. That's why I didn't bother taking it lower. It would have been covered up. 

Or do you mean covered up as opposed to just leaving the deflector off?


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## CutaLot (Jan 17, 2010)

Hey POSI, thanks for the great pics and how-to's. 

I just cut my 029 muffler similiar to your mod, and I am really pleased. Richened up the HS screw and she is a lot snappier with what feels like power to spare, and still pretty quiet. Cutting wood just got funner!


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## Positrack (Jan 18, 2010)

CutaLot said:


> Hey POSI, thanks for the great pics and how-to's.
> 
> I just cut my 029 muffler similiar to your mod, and I am really pleased. Richened up the HS screw and she is a lot snappier with what feels like power to spare, and still pretty quiet. Cutting wood just got funner!



Well, I'm about the last person around here qualified to give saw modification advice but I'm glad the pics helped. I got the camera for Christmas so I wanted to try it out anyway. 

Another update: I had the saw out today cutting hedge with a buddy who also has a 290, and I gotta say, this thing SHREDS now!  I could tell the MM helped the first time I tried it, but I really didn't realize just how much until I got to see it in action next to a stock 290. I think my chain might have been in a little better shape than his but still, it was obvious my saw was making considerably more power. I also noticed it was just a bit louder than I thought it was. My friend's saw is noticeably quieter, and as soon as I started it up he asked me just what the heck I'd done to it. :biggrinbounce2: I still like the sound of it though, and as soon as he saw how it cut he decided he might have to give it a try on his.

Also, I spent a fair bit of time tuning the high speed this morning and I still ended up with it about 1 7/8 turns out from seated.  I know that seems like a lot, and everything I've read suggests it should be more like 1 1/2 turns or so, but it sure seems like that's what it wants. If I turn it in much more than that, it only 4-strokes sort of intermittently, and the revs don't seem real stable (it surges a bit). At the 1 7/8 setting, it 4-strokes steadily and the revs are pretty stable. It also doesn't smoke anymore than it ever did as far as I can tell. I dunno... I'd have the dealer listen to it but he'd probably pass a stone if I told him I'd modified the exhaust and altered the carb limiters.  I guess I'll just check the plug every now and then and call it good for now until I can get somebody more experienced than me to listen to it. I sure don't want to run it too lean. Thanks to everybody for all the feedback; I really appreciate it.


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## Birdman1890 (Mar 24, 2012)

*My Ms290 muffler mod*

Runs great, I removed the limiter caps, and the retainer, that Stihl claims is a part of the carburetor. I cannot get that piece, but I did get new screwcaps, did not replace any of that. Did not modify the deflector place, but I did replace the screen. Drilled 1 big hole in the dimple, (center), and 4 smaller one's, around the perimeter.


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## Birdman1890 (Mar 24, 2012)

Why can't I post the pics of my muffler mod?


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## clintonior (Mar 28, 2013)

It would be nice if you could post the pic. i would like to see the final product. with the dimple drilled and the cut outs. which works best?


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## H 2 H (Mar 28, 2013)

Here another MS 390 MM


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## qbilder (Mar 28, 2013)

I modded my 390 & it made all the difference, like two different saws. Haven't done the 029 yet & probably won't because it has 4 ports stock and runs great as is. It's the reason I modded my 390. The old 029 would out cut the new 390. Not any more.


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## old-cat (Mar 28, 2013)

Your MS290 has 56.5 cc. When you decide you want a REAL chainsaw that's the same 56.5 cc but much lighter and more powerful AND possible less $$$ get your self an 034. It will make you REAL happy!!:cool2:


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## elkman1jc (Jun 2, 2013)

Did you have to pull out your limiter caps to get it tuned properly?


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## Beaverblade (Oct 12, 2013)

*tools*

What tools do I need for the muffler mod?


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## Beaverblade (Oct 12, 2013)

elkman1jc said:


> Did you have to pull out your limiter caps to get it tuned properly?



Since the mod will allow more air to exhaust through the muffler the fuel mixture for the carb will need adjusted more beyond factory setting to balance with the increased air flow.


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## Ironworker (Oct 12, 2013)

Beaverblade said:


> What tools do I need for the muffler mod?



A drill and a Dremel with a cutting disc.


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## jalpaugh1 (Apr 22, 2014)

Hey I know this is an old post but can someone "try" to explain "4 cycling" to me as referenced in this post. Thank you immensely.


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## mopar1rules (Apr 22, 2014)

old-cat said:


> Your MS290 has 56.5 cc. When you decide you want a REAL chainsaw that's the same 56.5 cc but much lighter and more powerful AND possible less $$$ get your self an 034. It will make you REAL happy!!:cool2:


Yep I agree! I have a 034 and LOVE it! Kills my dads MS290! IMO 034's are solid reliable older saws that are excellent for firewood cutting and easy on the wallet for a used unit.


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## [email protected] (Apr 22, 2014)

This is a good video by a fellow member

Listen to the difference in sound between WOT and loaded(sound it makes when cutting) someone else probably has better words to describe it, but the video should have what your looking for.


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## jalpaugh1 (Apr 22, 2014)

Yeah that's a big help Cory. Thank you. It's definitely gonna take some practice and trial and error but I think that will help me tune my own saws a little more accurately than I have been. It sure is just a subtle difference! Thx again.


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## [email protected] (Apr 22, 2014)

jalpaugh1 said:


> Yeah that's a big help Cory. Thank you. It's definitely gonna take some practice and trial and error but I think that will help me tune my own saws a little more accurately than I have been. It sure is just a subtle difference! Thx again.


Read up more before tuning; some saws have limiting coils. The sound of a limiter can be hard to distinguish from four stroking. Best bet is to start rich( heavy four stroking) and then work lean like the video depicts. Better rich than lean. If your saw is to rich you will find it four stroking more often than not. You'll want to tune in the cut.


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## roadiestar (Apr 22, 2014)

I have a Makita 6421 and the carb adjusters are epoxyed . How do you get them cleaned out ?


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## [email protected] (Apr 22, 2014)

roadiestar said:


> I have a Makita 6421 and the carb adjusters are epoxyed . How do you get them cleaned out ?


Hard work!!! Mine were not epoxied. Just had plugs in holes preventing adjustment. They are easy to get off. Just cut the flange on the back of the plug off and it will slide out. I've seen threads here with info on scraping out the epoxy. I haven't had to do that. Probably just have to scrape at it a while. Maybe you should ask in a new thread. Try to use the search function first. This muffler mod thread probably won't get a lot of attention. I've seen mention of using a soldering iron


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