Muffler mod... Not impressed

[daddy]

New to the forum, but will speak plainly in hopes of getting some honest feedback.

After spending about a week of evenings browsing the forums, I decided to cut some holes in my 7 year old ms290.

The saw has been good, and the only problem has been a cracked fuel hose, that I replaced recently.

I have always run an 18" .325 yellow stihl chain, and cut firewood for myself. Usually 8-10 cords a year, work shared now with my little 170 that I tend to run till I need the bigger saw.

Stihl oil in the black containers at recommended 50:1, Hi-test.

'Nuff background, here's what I did. I basically connected the two exhaust openings behind the screen to create a slot, and widened the slot a bit. I also chewed a bit off the deflector to open it some. I did not take the muffler apart, and did not change the openings of the internal baffles at all.

After putting it back on, I removed the limit stops on the carb adjusting screws, and followed Madsen's guide to retune it.

I do not have a tach, and do not claim to be any kind of small engine guru, but if it means much, the saw runs as it did before. Nice idle with no chain movement, good acceleration, and sounds the same as before. A little smoother when you are into a big cut and work it hard.

Bottom line is this: The saw ran great before, and it runs great now but I don't see the improvement that everyone talks about here.

Did I not go far enough with the openings? I wanted to stay fairly conservative, as it is a work saw, and read that most gains are had right away.

Do I need to have it tuned with a tach?

Are you guys all nuts?:monkey:

I really enjoy this place, and hope someone has some advice.

Pics included, and thanks in advance.

 

[fredmc]

Not enough, grind the crimp off and open up the baffle. Drill some more holes in the can behind the deflector. Remember the exhaust outlet should be roughly 80% of the exhaust port suface area.

 

[Scooterbum]

Read this thread, your not even close.

http://www.arboristsite.com/showthread.php?t=66105&highlight=290+muffler+mod

 

[Teddy.Scout]

WOW!
First welcome!
Second AWESOME!
First post and he is coming with pics! Modding, AWESOME!!

REP HIM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Arrowhead]

I agree... not enough. The deflector does not look bad, maybe a little more. I drilled two 5/16" holes in the indented part of the muffler in pic 1. I have a ms310 I did that to, it made a huge improvement.

 

[Rftreeman]

unless you open up the internal baffle, what you did was a waste of time and effort, open up the inside and retune and I'm sure you'll see a difference..

 

[nmurph]

there is no need to open the muffler to mod it. the area under this depression is straight shot to the exhaust port. there is no baffle to get in the way.

 

[bbdropshot]

New to the forum, but will speak plainly in hopes of getting some honest feedback.

After spending about a week of evenings browsing the forums, I decided to cut some holes in my 7 year old ms290.

The saw has been good, and the only problem has been a cracked fuel hose, that I replaced recently.

I have always run an 18" .325 yellow stihl chain, and cut firewood for myself. Usually 8-10 cords a year, work shared now with my little 170 that I tend to run till I need the bigger saw.

Stihl oil in the black containers at recommended 50:1, Hi-test.

'Nuff background, here's what I did. I basically connected the two exhaust openings behind the screen to create a slot, and widened the slot a bit. I also chewed a bit off the deflector to open it some. I did not take the muffler apart, and did not change the openings of the internal baffles at all.

After putting it back on, I removed the limit stops on the carb adjusting screws, and followed Madsen's guide to retune it.

I do not have a tach, and do not claim to be any kind of small engine guru, but if it means much, the saw runs as it did before. Nice idle with no chain movement, good acceleration, and sounds the same as before. A little smoother when you are into a big cut and work it hard.

Bottom line is this: The saw ran great before, and it runs great now but I don't see the improvement that everyone talks about here.

Did I not go far enough with the openings? I wanted to stay fairly conservative, as it is a work saw, and read that most gains are had right away.

Do I need to have it tuned with a tach?

Are you guys all nuts?:monkey:

I really enjoy this place, and hope someone has some advice.

Pics included, and thanks in advance.

I just did my 290 a couple nights ago, mine an older one like yours, I slotted it like you did, but then i drilled 3 3/16 holes right next to each other in the dimpled area and i made them into a slot so its a 3/16 by 3/4 slot, gonna try it out tommorow, I have adjusted the carb though it seems to wanna be out between 1 1/2 and 1 3/4 out on the H seems like alot of adjustment for no more of a mod than i did, wanted to start with that and see how i like it, maybe do more later.

 

[bbdropshot]

Not enough, grind the crimp off and open up the baffle. Drill some more holes in the can behind the deflector. Remember the exhaust outlet should be roughly 80% of the exhaust port suface area.

So if you slot out the two existing hole does that not count for the 80% since it still has to go through the baffle

 

[little possum]

The indented part is gone on the remaining 029supers here. They will sing to you.

Do a little more grinding, and I am sure you will be a little bit happier

 

[mowoodchopper]

there is no need to open the muffler to mod it. the area under this depression is straight shot to the exhaust port. there is no baffle to get in the way.

I agree it should look like murphs!

 

[Erick]

there is no need to open the muffler to mod it. the area under this depression is straight shot to the exhaust port. there is no baffle to get in the way.

This is what you want to do with it. open that sucker up.

Actually you've already connected the two lower passages, just pop a 1/2" hole in the middle of the upper indent, retune and enjoy.

I like to grind a little more off the deflector and take it all the way back to the bends/lines.

Like this.....

BTW just to make sure cause nobody’s said it yet..

Make sure to remove the muffler from the saw before drilling and make sure you clean all of the drill fines and grinding dust out of the muffler before you put it back on.

Yeah, I know... but you'd be surprised.

 

[southbound]

I copied nmurph's design and it was like night and day.....

 

[Burvol]

It's a MS 290

What did you really expect? Major power?

 

[JohnnyBoy1986]

murph pretty much has it down for the MS290, your idea was a good start but nowhere NEAR enough to get the job done. The MS290, 310 and 390's will wake up seriously with a good muffler mod! you just need to go back to the drawing board and have a little more faith, you seem a little disappointed and maybe even frustrated that it didnt work out yet, BUT when you get it right, you'll be praising every1 around here, TRUST ME! Remember, if at first you dont succeed, try try again! Good luck with it. :greenchainsaw:

 

[sbhooper]

What is the suggested WOT rpms on the 290? My buddy has one and I am going to talk him into modding it after reading this info. 13,000?

 

[daddy]

Second attempt.

Well folks, I took your advice and went a bit further, and as murph suggested, I drilled a 1/2" hole in the center of the dished area that is not baffle restricted.

Retuned, and walked out to the wood shed.

This time I can tell the difference. It sounds throaty, but not obnoxious, and definitely cuts better.

I forgot to mention in my first post, that one of the reasons I looked into this is that I picked up a 20" bar the other day, and was hoping to be able to run it half decent with this saw.

I had some rounds of knotty red pine big enough to bury the bar, and I gave it a whirl.

At this point, it runs the 20" bar about like it used to run the 18", and it is actually pretty fast with the 18".

I'm tempted to go further, but I think I'll cut a few cords first to see what I think.

I don't want to make this thing too loud. I am an equipment operator, and already wear earplugs all the time.

I am going to stop by my local saw shop and have him check my tune this week.

I do think some of you guys may tend to overstate things a wee bit :chainsawguy:, but you are addicted to saws, and this is the internet:hmm3grin2orange:

Just pokin' fun, seriously, thanks for the help and suggestions. I do appreciate it. Nice group here.

 

[southbound]

Looks better all ready...In a week or two you will find yourself thinking what if I drill another hole????

 

[matt9923]

looks good, I opened mine up, doesn't take to long. Woke up my 039 pretty well.

heres mine, quick mod.

http://www.arboristsite.com/showthread.php?t=107556&highlight=039+mod

 

[nmurph]

Well folks, I took your advice and went a bit further, and as murph suggested, I drilled a 1/2" hole in the center of the dished area that is not baffle restricted.

Retuned, and walked out to the wood shed.

This time I can tell the difference. It sounds throaty, but not obnoxious, and definitely cuts better.


I'm tempted to go further, but I think I'll cut a few cords first to see what I think.

I am going to stop by my local saw shop and have him check my tune this week.

looks good. you are probably close to max and you are probably going to experience diminishing returns if you go much larger.

my mod was 4-5.5mm holes, 1-10mm hole and 2-11.5x8mm ovals.