# 029/290 muff mod - found the sweetspot



## LazyJ (Apr 6, 2008)

I proceeded slowly and in multiple steps taking care to test each phase thoroughly with several tanks of gas, kept in good tune, and loaded up in big wood.

First I just reamed out the two existing slots and opened up around the deflector shield exit a good bit, this did very little for performance and the exhaust note hardly changed. 

Next I drilled a 5/16" hole in the indented area of the muffler directly inline with the exhaust port which bypasses the internal baffle, surprisingly the increase in throttle response was obvious, running good, sound still well under my Db tolerance.

Today I took a rat file to the 5/16 hole and made it into a slot. Outstanding throttle response, pulls chain alot faster under load, sounds cool with a good "pop-pop" at idle and a tolerable Db at WOT.

I ran two tanks today with a goofy grin on. It sounds and runs so different I decided to pull the plug to make sure I had the carb dialed in right. There's more tan than what this pic shows but it's still whiter than I've ever seen it.

Threw a new NGK in it and opened the H screw just a sniggle, cleaned her up and took pics







Here you can kinda see the increased size of the exhaust exit






Good-looking 10 year old boat anchor


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## Ray Bennett (Apr 6, 2008)

good job.


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## stihl 440 (Apr 6, 2008)

*029*



Ray Bennett said:


> good job.



+1:greenchainsaw:


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## RiverRat2 (Apr 6, 2008)

Ray Bennett said:


> good job.



+ 2!!!!!! Yep Repped him good!!!!!


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## NPKenny (Apr 7, 2008)

In my only experience with a 290, you are just getting there. I opened the entire indented area in the muffler and drilled ~4 small holes in the cover. I also opened up the existing outlet on the cover.

If you dind't put the deflector cover back on, then it should be good. If you did put the deflector cover back on over the holes you drilled, I think you still have a bottleneck.

I had to really open the H screw to keep up with the muffler on that saw. It went from being a very poor saw to being a an impressive tool with just the muffler mod and tuning in the carb.


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## OilHead (Apr 7, 2008)

Open up the recessed area all the way & drill a 1/2 " hole thru the front side angle cover . That small exit after a 90 degree turn is a bottle neck. You will be surprised how much exhaust is comming out the front from 1 foot away.


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## OilHead (Apr 7, 2008)

Yeah open it up some more - 13,000 rpm just dont toast the sucker because its too lean. Swing by a saw shop if you dont have a tach to confirm it.


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## windthrown (Apr 7, 2008)

I did a similar job on my Ebay spare 290 muffler, except I opened up the slots and drilled several smaller (1/8th inch) holes into the dented section. I also cut the cover baffle at a 45 degree angle and opened up the exit port on that quite a bit, but keeping the exhaust ported at an angle. Not quite full throttle, but I wanted to keep it somewhat quieter than a helicopter taking off. I opened up the H screw about 1/2 turn over factory, and I run it a tad rich. It woke the saw right up. I am leaving the saw here with the ex-GF though, so I will put the factory muffler back on and detune the carb. Then I will probably sell the modified muffler on Ebay. 

Divorce is a b1tch...


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## SectorB (Oct 3, 2008)

So I modded the 029 super muffler the way LazyJ has done and I also drilled 3- 1/8" holes in the cover just below the exhaust port so it wouldn't bottle neck the gases. I turned the saws H&L screws counterclockwise to start and tune, but it seems to be running fine. IS this normal?? I haven't removed the limiter caps. I did have to adjust the idle to keep it running but that was it. I will post a vid or pics when I can.


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## WidowMaker (Oct 5, 2008)

Here, if I can do it, is shot or two of my 029 Super. Pretty much same as yours. Really woke my saw up, haven't had a tack on it, adjusted the H jet to about 1 1/4 turn and the L jet to about 5/8 turn Has ran a season, cut about 10 cords of wood. The Piston from the exhasut port still looks like new. A little carbon in the exhaust port for some reason.


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## superfire (Oct 5, 2008)

*howy cheeze maker*

widowmaker you went ape sheet crazy:jawdrop: lazy looks good for a proby muffler hacker. me i think any stock saw sucks. i wait until warranty goes then i goe nutz. my 260 pro is a skreamer with high speed skrew mod and muffler mod. to bad she finally needz to be rebuilt, she is my favorite saw 

 :greenchainsaw:


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## stihlboy (Oct 5, 2008)

*thank you for this post*

this is what i have been looking for for quite a while


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## WidowMaker (Oct 5, 2008)

Some of the wood the above has cut..


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## WidowMaker (Oct 5, 2008)

Added a shot to show how I open up the LH side of the cover for more outlet area.

===

Thought I added this to the above post... sorry


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## SectorB (Oct 5, 2008)

Here is the 5/16" in the muffler





I drilled 3-1/8" holes in the cover






Is this to mild to do have any real gains? Like I said, the H and L were turned all the way counterclockwise and it runs, I just don't know the RPMs. The La was adjusted to make it idle better. I want to do this right, any suggestions?

Thanks


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## woodyman (Oct 5, 2008)

This is the one Gremlin did on the MS310 I no longer own.Same muffler as 029,MS290,he gutted it out and added extra pipe out the side and left the stock exhaust.It out cut my brothers MS361 and sounded sweet too.I brought i



t to local dealer for carb adjustment.


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## nmurph (Oct 6, 2008)

here's what i did on my 310, 4 - 3/16" and 1 - 3/8". i keep thinking of opening it up some more, but i don't want to get too greedy. i know there is a point of diminishing returns, i just don't know where it is with this muffler. my currently mod opens the muffler to about 70% of the exhaust opening, as best as i could measure. it really does make a difference on this saw, and i suspect the 290 and 390's as well. i would like to find a 390 p+c to put on my saw. i think i would be getting close to 5 hp. the difference bw the bf and after of my mod feels like the difference bw way it ran bf the mod and my brother's rancher 55, and it sounds cool. definitely louder, but tolerable.
i bought a can of high temp paint, i just have not taken the time to finish the job.


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## blsnelling (Oct 6, 2008)

Go too far and you may have idle problems.


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## nmurph (Oct 6, 2008)

one thing i have done was to retune it a couple of times after modding it. the first was for a little hesitation coming off of idle, the second was to take away a " wee little bit" of the blubber at the top. it still has plenty of 4 stroke, though. i have it running perfect now. it has not needed more tuning for the last 25 hours, or so. 
one thing i think that i have noticed is that it cranks better. this may just be a coincidence, but it will now "hit" on the second pull, and start on the third if it has been run the previous day. if it has been more than that, it will hit on the fourth or fifth, and run on the next pull. this is consistantly two to four pulls sooner. fuel is the same, however i have changed to the Ultra oil.


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## woodyman (Oct 6, 2008)

Looks like you opened it up just right.The stock hole on my MS310 was so small I dont see how it put out the advertised 4.0 HP.A muffler mod on the MS290,MS310,MS390 really wakes them up.I added two extra 3/8s holes to my 026 and adjusted the carb.I took it out yesterday and took down a 13" red oak and Im thinking now I might not see too much use out of my muffler modded 359,that 026 really cuts with a sharp chain(it came with a yellow .325 chain,it look like they were cutting rocks with it,with about 60% left on it and after 30 passes on each cutter with the file and taking down the rackers a bit it rips)a sharp chain makes a big difference.Hey Brad do you ever leave your PC?Just kidding,you have been alot of help to me.


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## blsnelling (Oct 6, 2008)

woodyman said:


> Hey Brad do you ever leave your PC?Just kidding,you have been alot of help to me.:clap:[/QUOTE]
> 
> Only when I'm in the garage working on a saw, LOL. I have a desk job and just frequently check the forum.


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## chainsaw1 (Oct 6, 2008)

I dont know if their is a saw out their that was choked off more than that MS650 when i got it, but after the port job it really really brought that to life also, but now with the BB kit it should be even better yet.


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## peter399 (Oct 6, 2008)

LazyJ said:


> Good-looking 10 year old boat anchor



Indeed in good shape.


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## LazyJ (Oct 6, 2008)

SectorB, taking close note when I took my limiter caps off my H jet was limited to open only to about 7/8ths of a turn out, with muffler mod its now set to almost 1.5 turns out. Search on how to remove the caps and git-r-done before you melt a piston. Probably won't gain much power until you turn the fuel up anyway.


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## stihlboy (Oct 6, 2008)

*Wild Mod*







i found the pipe in my garage it went to a motor scooter


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## Richard_ (Oct 6, 2008)

where can I buy ab already modded muffler for my MS 290 ??


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## Poley4 (Oct 6, 2008)

stihlboy said:


> i found the pipe in my garage it went to a motor scooter



Um.....................................that's different.


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## nmurph (Oct 7, 2008)

Richard_ said:


> where can I buy ab already modded muffler for my MS 290 ??



i don't know where you can buy one, but if you have a drill and a grinder you can do a very effective mod in about 10 minutes, start to finish. then about another 10 to tune the carb.
look at pics in post 17, above.


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## SectorB (Oct 7, 2008)

LazyJ,

I took the saw over to the shop to see what type of RPM's it was turning.

Idle was 3000 at WOT it was 13000 and some small change. I took it today and ran through some hickory with no problems. The saw is running great, but maybe a little more fuel will really help. Thanks for the info.

Sector


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## nmurph (Oct 7, 2008)

B,
i took my limiter caps off by using a sheetrock screw. i have heard some say they damaged theirs using this technique, but i did not have a problem. once they were out, i took a razor and trimmed the tabs off and tuned it. don't forget to put the caps back on, as they keep the screws from moving from vibration.


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## stihlboy (Oct 8, 2008)

Poley4 said:


> Um.....................................that's different.



yep but it works awesome


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## SectorB (Oct 9, 2008)

Lazy and Murph,

Took the limiter caps off, tuned it and it is running at 3000 and 13000 and sounds like a much better saw. Thanks for all the info.  Now i need to get a new chain. I hit a grown over pipe and ripped off a lot of cutters


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## Bruce Hopf (Oct 9, 2008)

I'm planning on buying a Stihl 044, here in the very near future, for rebuilding, and for my use. I also am planning to do a Muffler Modification, as well.
I never knew, or never heard of Muffler Modification, until I joined AS. Can you fellas, tell me which design that you guys were so nice to post pictures, would be the best suited for this 044. I mostly cut Soft Maple, and Ash here in my Bush. All the help, and advice I can get is Extremely Appreciated. Thanks in advance for your help. Bruce.


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## blackoak (Oct 10, 2008)

Bruce Hopf said:


> I'm planning on buying a Stihl 044, here in the very near future, for rebuilding, and for my use. I also am planning to do a Muffler Modification, as well.
> I never knew, or never heard of Muffler Modification, until I joined AS. Can you fellas, tell me which design that you guys were so nice to post pictures, would be the best suited for this 044. I mostly cut Soft Maple, and Ash here in my Bush. All the help, and advice I can get is Extremely Appreciated. Thanks in advance for your help. Bruce.



Bruce does your 044 have a DP muffler on it, if not get one and you should be set to go as far as a muffler mods on an 044. Richen up the high side a little and let her rip.


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## Bruce Hopf (Oct 10, 2008)

black oak said:


> Bruce does your 044 have a DP muffler on it, if not get one and you should be set to go as far as a muffler mods on an 044. Richen up the high side a little and let her rip.


Now you have me lost. LOL. How do you tell if you have a DP Muffler, from the other? As you know, I'm new to this Muffler Modifications. Thanks Bruce.


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## LazyJ (Oct 10, 2008)

Bruce, here's some pics I posted of the DP cover.

http://www.arboristsite.com/showthread.php?t=72458


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## Bruce Hopf (Oct 10, 2008)

Lazy J said:


> Bruce, here's some pics I posted of the DP cover.
> 
> http://www.arboristsite.com/showthread.php?t=72458



Thanks for the Picture Post. I'll just wait, and see what happens first once I get this 044 up and running, before I do any of this fancy work. 
I might be not Bold enough to try it, until I get used to the Chainsaw First. The piston was seized, but with some real good penetrating oil, I was able to get it freed. Bruce.


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## Bruce Hopf (Oct 12, 2008)

I took the Muffler off my Sthil 044, that I just Bought, and it didn't look anything like the Pictures posted here, Once I got the Plate off the Muffler, you could see the Exhaust Port. Is that supposed to be like this for a 044? Here are some Pictures of the Muffler. Your Advice is Greatly Appreciated. Thanks. Bruce.


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## mickeyd (Feb 19, 2009)

I did a similar job on my muffler mod tell me how you adjusted the carb.
thanks mick


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## Medman (Aug 19, 2009)

*Newbie process to the muffler mod*

I started to cut this morning and it started to rain hard so I found my self with some time to do some maintenance on my 029. Then I saw my drill and the rest was history. 
I ran into some problems tuning it up but i think that i am close. I have the burble sound at max rpm. the response is great. 
Now I am ordering a tach just so its right.
I haven't had a chance to test it on my 33 cord pile yet but tomorrow is another day. 
I just want to say thanks to Lazy J for the pics. And to all the long time members of the site for all the information. 
I have been a weekend warrior for many years and never knew how chains and mods could boost the performance. 

P.S. What should my rpms be on a 029 with the muffler mod?\

Thanks again Lazyj and everyone.


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## SectorB (Aug 20, 2009)

At WOT my RPM's are 12,500. I went to my Home Depot and the tool rental shop put it on the tach. The thing runs sweet and sounds great.


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## stinkbait (Aug 20, 2009)

So was the plug to light in color? I know that it shouldn't be white, but is a light tan fine? I didn't see where that question was answered.


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## little possum (Aug 20, 2009)

The indented part on the front of the muffler, is completely gone on mine. Did it the same way as Dads, and its been run pretty good. No problems yet.


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## nmurph (Aug 20, 2009)

tachs are useful for setting up saws that have rev-limited coils. other than that, saws should be tuned by ear. when you mod a muffler the max rpm where a saw can 4 stroke will change.


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## Medman (Aug 20, 2009)

*plug color*

The plug that was in the saw was dark. I modded the muffler and now it is a tanish color.

thanks again for all the advice.
Tim


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## Medman (Aug 20, 2009)

Murph,
when you say 4 stroke do you mean the gurggle at wot. Thanks


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## nmurph (Aug 20, 2009)

yeppers.............4 stroke......miss...........checking the plug color is good if you shut it down in the middle of a cut........


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## Medman (Aug 20, 2009)

Thanks murph.


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## bobd80toy (Mar 5, 2010)

i know no one has posted here in a while but i just wanted to say thanks to everyone posting the pics and there in put.

i just picked up a 2006 ms390 for $245 and i didnt even have the saw for an hour and started cuttin into the exhaust!  i was fine with the power it had....but hell, you can never have to much.

i first drilld a 3/8 hole in the indented part and a few 3/16 else where but didnt notice much difference but then i cut away some on the cover plate and noticed a big difference as soon as it started! thanks again!


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## southbound (Mar 5, 2010)

Welcome aboard!!!!!!!!!!!!!

This is just the beginning :hmm3grin2orange::hmm3grin2orange::hmm3grin2orange:


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## nmurph (Mar 5, 2010)

bobd80toy said:


> i know no one has posted here in a while but i just wanted to say thanks to everyone posting the pics and there in put.
> 
> i just picked up a 2006 ms390 for $245 and i didnt even have the saw for an hour and started cuttin into the exhaust!  i was fine with the power it had....but hell, you can never have to much.
> 
> i first drilld a 3/8 hole in the indented part and a few 3/16 else where but didnt notice much difference but then i cut away some on the cover plate and noticed a big difference as soon as it started! thanks again!



congrats......i hope you adjusted the muffler. if not, you will soon be learning how to rebuild a clam-shell.


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## bobd80toy (Mar 5, 2010)

nmurph said:


> congrats......i hope you adjusted the muffler. if not, you will soon be learning how to rebuild a clam-shell.



i think you mean carb....


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## nmurph (Mar 5, 2010)

bobd80toy said:


> i think you mean carb....




nope........got to adjust the muffler bearing. very few people know that these saws utilize them.


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## bobd80toy (Mar 5, 2010)

wanna show me where the blinker fluid goes to??


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## ri chevy (Aug 31, 2012)

*My Stihl 029 Muffler Mod*

A couple of photos of my Stihl 029 Muffler Mod. The inside has a few holes also.


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## blk90s13 (Sep 4, 2012)

Anyone care to walk me through adjusting a carb ? I am wanting to do the muffler mod to the ms290 I picked up yesterday but want to be able and adjust the carb as well 


Muffler bearing adjustment ? that is a joke right ?


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## ri chevy (Sep 4, 2012)

*Carb tuning*

Saw Carb Tuning


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## blk90s13 (Sep 4, 2012)

ri chevy said:


> Saw Carb Tuning




Thanks you, that was quick


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## cheeves (Sep 4, 2012)

LazyJ said:


> I proceeded slowly and in multiple steps taking care to test each phase thoroughly with several tanks of gas, kept in good tune, and loaded up in big wood.
> 
> First I just reamed out the two existing slots and opened up around the deflector shield exit a good bit, this did very little for performance and the exhaust note hardly changed.
> 
> ...


Did very similar work to my brother's 029 and my 310. Like totally different saws now!! IMHO 2 excellent firewood saws!


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## blk90s13 (Sep 4, 2012)

Done in 3 minutes with the Dremel tomorrow morning I will start it up and try to adjust the carb 




View attachment 251481
View attachment 251482


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## blk90s13 (Sep 8, 2012)

blk90s13 said:


> Done in 3 minutes with the Dremel tomorrow morning I will start it up and try to adjust the carb
> 
> 
> 
> ...





I finally got to use my ms290 today for the first time :msp_w00t: its a monster, and sounds awesome after the muffler mod


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## ri chevy (Sep 9, 2012)

*029/290 muffler mod and carb retune*

Cool. :msp_thumbsup:


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## fearofpavement (Jan 21, 2013)

Does the 039 and 029 use the same muffler? I saw earlier in the post that the 029 and 031 were the same, just wondering.


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## redunshee (Jan 22, 2013)

fearofpavement said:


> Does the 039 and 029 use the same muffler? I saw earlier in the post that the 029 and 031 were the same, just wondering.



Yup.


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## Aaron441 (Jan 22, 2013)

fearofpavement said:


> I saw earlier in the post that the 029 and 031 were the same, just wondering.



029 and 031 are not the same in any way at all. 029, 039, MS290, MS310, and MS390 are the 1127 series. Almost all of their parts interchange. The 031 is much older and a totally different animal.


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## fearofpavement (Jan 22, 2013)

So if the 029 and 039 use the same muffler, wouldn't the 039 benefit even more from a muffler mod since it is trying to cram more exhaust out the same size holes the 029 is supposedly limited by?


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## H 2 H (Jan 22, 2013)

fearofpavement said:


> So if the 029 and 039 use the same muffler, wouldn't the 039 benefit even more from a muffler mod since it is trying to cram more exhaust out the same size holes the 029 is supposedly limited by?



I have several mufflers for that series

I've done several different things to the inside of them 












By far the best move I made was to pull the baffle completely out and open the exit port to the same size as the inlet


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## grinder1 (Mar 29, 2013)

*removing limiter caps*

i have a stihl 290 i need to remove the limiter caps from. Any help?


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## H 2 H (Mar 29, 2013)

grinder1 said:


> i have a stihl 290 i need to remove the limiter caps from. Any help?



The red caps ?

I use a drill bit just a little smaller than the opening and a drill motor 

Use a drill motor with the bit just smaller than the hole run it in till you fill it hit the adjustment screw and back the needle valve all the way out and take off the back side of the plastic limiter; put the needle valve back in till it hits lightly than one turn out is a good starting point to retune it

View attachment 287497


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