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MS290 muffler mod

Post in 'The Gear' started by ikessky, Jan 18, 2010.

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  1. ikessky

    ikessky Minister of Fire

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    Well, after a having the saw for close to a year and doing a bunch of reading on muffler modding, I finally decided to go a head and do it. I should have taken some pictures, but didn't really have the time since the littlest one was chasing the dog around the garage while I was trying to work! Basically, I combined the two existing slots into one large opening. It's not straight piped like a lot of the ones you see, but I may take it apart again and add one or two small holes in that area. I sliced the tabs off the red limiter caps and the reinstalled them, set the L screw to about 1 turn out and the H to 1.5 and tuned from there. It's probably still a little on the rich side, but I didn't want to over do it since I didn't have a tach to use.

    All in all, it wasn't a hard job and I might have picked up a little power from it. Hard to tell since I didn't really have any wood laying down to really try it out and I didn't want to go out felling trees with a 1-year-old tagging along!

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  2. HittinSteel

    HittinSteel Minister of Fire

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    Post up some pics when you get a chance....... there still may be a lot of gains left in the saw depending on the size of the opening
  3. smokinj

    smokinj Minister of Fire

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    +1
  4. ikessky

    ikessky Minister of Fire

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    So I should probably just add a few holes into the depression and tune it again? The mod I did still puts the exhaust through the baffles.
  5. HittinSteel

    HittinSteel Minister of Fire

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    Here's how I did mine (and several others). I put the screen back in after the picture.

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  6. smokinj

    smokinj Minister of Fire

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    post a few pic's it will really help
  7. Highbeam

    Highbeam Minister of Fire

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    I was running my saw, the 290, two days ago felling some junk trees. When shortening the stumps I noticed that the mufflers on these saws are very quiet. The intake suck sound is very loud. I expect that you could open up that OEM muffler quite a bit before even being able to hear it over the intake.
  8. smokinj

    smokinj Minister of Fire

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    that looks good
  9. smokinj

    smokinj Minister of Fire

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    heres mine

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  10. ikessky

    ikessky Minister of Fire

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    The exhaust is taking the path of least resistance right? So, I should be able to add a couple smaller holes in the depressed area above the baffle and not hurt anything right? If these holes cannot flow all the gasses, it will then take the path through the baffle. Is my thinking correct here?
  11. smokinj

    smokinj Minister of Fire

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    hittensteel has it perfect I Would rather have one opening.
  12. southbound

    southbound Minister of Fire

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    Did you open up the cover any???

    I drilled into the depressed area and opened up the out on the front cover as well....
  13. ikessky

    ikessky Minister of Fire

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    Not my picture, but this is basically what I did. My opening is straight across though. I didn't make the small vertical leg like this guy did.

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  14. southbound

    southbound Minister of Fire

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    That seems to be a popular way of doing it....Should work fine....

    I got a 064 muffler that needs a pipe welded on the side....Gonna have to pay someone for that tho....
  15. smokinj

    smokinj Minister of Fire

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    Now do you know how to tune it you opening should be enough?
  16. ikessky

    ikessky Minister of Fire

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    I took my tuning process from the Madsen's site. Tuned the L screw to a point halfway between where it starves for fuel and where it loads up and runs the chain. Tuned the H screw to a point where it is 4-stroking at WOT no-load. Like I said before, I'm not sure but I might have it a little richer than it needs to be as I didn't think that the 4-stroking went away when I put it into wood. Then again, I tried it on a half rotted piece and a few pieces of 2x12 lumber.
  17. smokinj

    smokinj Minister of Fire

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    your dead on track better to be on the rich side. Best to listen to it in the cut and make adjustment from ther if need be.
    You should be able to notice a diffrence in the larger wood when the bar is baried
  18. ikessky

    ikessky Minister of Fire

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    I'm going to open the slot up a little more and then do some more tuning when I can get into some actual larger hardwood. I think my FIL has some sitting by his OWB that he wouldn't mind me cutting, so that should help me out as I'm not going to be trudging through the woods in the snow right now.
  19. smokinj

    smokinj Minister of Fire

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    A total of 1/2-9/16 opening is the sweet spot for a 55cc saw. my 460 is at 3/4 opening its 77cc
  20. ikessky

    ikessky Minister of Fire

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    I assume you are talking square inch opening? Removing and reworking the muffler is pretty easy, so maybe I'll take it back off and do some measuring.
  21. smokinj

    smokinj Minister of Fire

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    I am talking about the opening in the cover only
  22. ikessky

    ikessky Minister of Fire

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    The deflector? Yeah, I didn't open that up a lot. I still could take some off of it to.
  23. smokinj

    smokinj Minister of Fire

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    if your opening is line up with the deflector it should be as good as it gets
  24. ikessky

    ikessky Minister of Fire

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    So do you think that drilling a hole in the depression would hurt now that I've opened the slots up? Would I have too large of an opening at that point?
  25. smokinj

    smokinj Minister of Fire

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    get a measurement and see where your at.....?
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