The Forestry Forum

General Forestry => Chainsaws => Topic started by: thutch85 on March 01, 2017, 10:09:48 PM

Title: muffle mods
Post by: thutch85 on March 01, 2017, 10:09:48 PM
has anyone done a muffler job on a MS291? im trying to decide if it makes enough of a power increase to bother doing. mine runs and starts great so unless it really does make a noticable difference i won't bother.
Title: Re: muffle mods
Post by: ButchC on March 02, 2017, 08:20:12 AM
Never owned a 291 so personal experience is zilch however most saws produced in the last 20 years or so will respond well to opening up the muffler. I have never seen it hurt power. Simply removing the screen often results in a nice boost. Letting the exhaust flow lets the saw breath easier which will translate into longer life.  Some times it will affect the carburetor adjustments to the extent that the limiters need to be tweaked. Guess the bottom line is I have never opened one up and wish I hadn't.
Title: Re: muffle mods
Post by: BobbyJr on March 02, 2017, 02:40:15 PM
Once you do a simple muffler mod and readjust the carb,you will be doing it to all your saws. You will get hooked just like all of us have. It is a nice positive move for you and your saw. More response,more power,and a little louder. I always wear quality headgear. Have fun!!
Title: Re: muffle mods
Post by: Bandmill Bandit on March 02, 2017, 09:21:46 PM
ALL mods that IMPROVE air flow are a should do for a responsible owner of 2 cycle powered equipment.

It is the first line of emissions reduction that the EPA just doesnt get.

Pretty much applies to ALL internal combustion engines!

Stuff cotton up your nose and see how long you last under a moderate to heavy work load.
   
Title: Re: muffle mods
Post by: 20ozjolt on March 02, 2017, 10:52:16 PM
is there a way to do this and still meet the forest service spark arrester requirements?
Title: Re: muffle mods
Post by: Bandmill Bandit on March 02, 2017, 11:00:32 PM
is there a way to do this and still meet the forest service spark arrester requirements?

Yes BUT you need some one that knows how to improve the breathing and still maintain proper back pressure at the same time. Some one that know how to calculate expansion chamber design/mod can help out with getting it right.  And it doesnt mean a huge competition type exhaust system.
Title: Re: muffle mods
Post by: thutch85 on March 02, 2017, 11:12:12 PM
im sold. i started with the carb, no point in opening up the exhaust until i can adjust the jetting, and mine has metal restricter caps instead of the red plastic ones.  😲 there seem to be pins holding them in place that would have to be drilled out. has anyone else run into these?
Title: Re: muffle mods
Post by: BobbyJr on March 02, 2017, 11:17:46 PM
If I remember correctly. On a stock saw, you can go up to 80% the size of the exhaust port of the jug. I think Im correct on this. I did this on my 660 and 026 and 260 And they all run great! Once you do this,you'll be hooked and you'll want to do all your saws like that.
Title: Re: muffle mods
Post by: Bandmill Bandit on March 02, 2017, 11:21:23 PM
im sold. i started with the carb, no point in opening up the exhaust until i can adjust the jetting, and mine has metal restricter caps instead of the red plastic ones.  😲 there seem to be pins holding them in place that would have to be drilled out. has anyone else run into these?

my husky has black plastic caps and I filed the little pin down so that they would allow the plastic caps to come off and still provide enough friction to keep them in place. has been working good so far. The caps are probably not needed but it still "looks" like a factory set saw this way.
Was a pain in the neck to do.

Bobby you numbers ring a bell and you need the spark arrestor to be calculated large enough so that the open space of the screen is equal to that figure. stainless screen with the same spec as original screen works best
Title: Re: muffle mods
Post by: thutch85 on March 02, 2017, 11:45:34 PM
drilled out the pin. it doesn't seem to be whats holding the cap in place, it was what stopped it! fully adjustable now! taking the muffle to work to open it up and blow it out in the morning. results to follow.
Title: Re: muffle mods
Post by: BobbyJr on March 03, 2017, 07:28:06 AM
If you can,match the exhaust gasket to the exhaust port of the jug. Then match the exhaust port on the muffler to the gasket. Be sure to thoroughly clean the muffler before you put it back on. You will be happy. Have fun!!
Title: Re: muffle mods
Post by: thutch85 on March 05, 2017, 01:27:29 PM
Well, the muffler mod was a success! I was really impressed with the increase in torque when getting into bigger wood, made for much faster cuts. started a pull or 2 sooner than i expected and idled fine while i moved logs and branches to get to the next cuts. very happy with the results, thanks for the advice