Saw builders - Muffler mod - what size holes are best?

[country]

I have an MS290, and want to mod the muffler. I have read the posts on how to do this, but would like some idea of how large to cut open the holes before I just start cutting. The exhaust port is a certain size, and the muffler has specific size holes to provide backpressure, etc. Is there a way to figure out what size holes will still provide the best performance? My thinking is something less than completely open, in other words, some backpressure is still desireable.

Is there some way to figure this out, or should I just guess by starting at 50% of the exhaust port size, or %60? Any suggestions?

FYI, this is the only performance modification I'm looking to make.

 

[Lawn Masters]

I'd recommend making a hole about 50% of the port size, then you will maintain decent backpressure, and gain some power too.

 

[Crofter]

Start on the safe side and try it. It is easier to make it a bit bigger later than to try to heal it up if you go too large. Remember that doubling a holes diameter gives 4 times the flow. Opening up the exhaust will require mandatory carb readjustment or your saw will run excessively lean.

 

[Lobo]

Muffler mod's

Just curious, you gentlemen who run mod saws constantly do you prefer round openings in the muffler, or square ones, or rectangular ones.

Does the hole config. really make any difference ?

 

[Crofter]

Depends on the area you have to work with. A round hole is easier to drill. The square drills are harder to come by, lol. Sometimes the shape that works best is an elongated hole got by drilling two holes and cutting out the divider. Sharp corners are more prone to cracking, but it is only the effective area that counts unless the exhaust must be directed a certain way to keep it off plastic or fingers.

 

[sawdust]

muffler mods

I have a Poulan 2300/ Compact 23 Husky I was looking at opening up the muffler gas exits on. It has a screen between 2 baffles and no exit holes. Does it just leak out between the body and the cap? I don't get it. How would you mod this one? It's a nice pruning saw but a little more power wouldn't hurt.

 

[Mange]

I have a Poulan 2300/ Compact 23 Husky I was looking at opening up the muffler gas exits on. It has a screen between 2 baffles and no exit holes. Does it just leak out between the body and the cap? I don't get it. How would you mod this one? It's a nice pruning saw but a little more power wouldn't hurt.

Could you post a pic or two of this saw?

 

[Elmore]

Just curious, you gentlemen who run mod saws constantly do you prefer round openings in the muffler, or square ones, or rectangular ones.

Does the whole config. really make any difference ?

heh heh, I like mine more than half as tight as the port and with a little pubescence around the edge. heh heh

 

[njforestfire]

i currently have both my 365 and 036 opened up to about 80% of the exhaust port size...they both RIP now!!! I noticed a big difference in performance on both...probably more so on the Husky.

 

[scottr]

baffle

Sawdust , if you look a little closer you will see that the exhaust is turned 90 degrees then it flows about 2" then turns 180 degrees then flows about2" then turns 90 degrees to exit the muffler . That is what the 2000 model does and it is probably the same on your saw . Give this a try , take out the two baffle plates and leave in the screen and remember to adjust the carb .

 

[sawdust]

Thanks scottr & mange

I went out to take some pics this am of the muffler on the 2300. There wasn't one hole, there were 10 holes in the outside plate.
Apparently the holes I couldn't see are in my head, allowing the sawdust to replace my memory brain cells. Or I couldn't see the holes cause the muffler was in the way. Will try your suggestion scottr. Thanks for the imputs guys!