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Muffler Mod for the 290,310,390

Post in 'The Gear' started by southbound, Jan 22, 2011.

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  1. southbound

    southbound Minister of Fire

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    A safe guideline is to go no larger than 80 % of your cylinder exhaust port. You have to measure and calculate the area of both and figure out how much more you need to open your exhaust hole.


    From another site it seems that 6 .25 hole are pretty normal for a 290..

    Now not recommend by me but this comes from someone with way more experience then I " ultimately, your trying to IMPROVE the flow of the muffler. If the INLET of the muffler is 800 cubic mm, and the outlet of the muffler is 100 cu mm, there's an OBVIOUS restriction... try and land your outlet size close to 80% or so of exhaust port (at the cylinder wall) size... you can go up to 100% if your still using the spark screen..."

    As for the 046 running a 3/4 inch port I bet if I measure the hole in my dp and the factory holes on the side it will be well over 3/4 inch and that is all factory no mods by me... Now I know you got one of those expensive modded muffs but I would be willing to bet it could be opened a little more...


    O and I was a BIG fan of Savinelli back in my smoking days.......I got a alligator that I loved....

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  2. smokinj

    smokinj Minister of Fire

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    [quote author="southbound" date="1297416430"]A safe guideline is to go no larger than 80 % of your cylinder exhaust port. You have to measure and calculate the area of both and figure out how much more you need to open your exhaust hole.


    From another site it seems that 6 .25 hole are pretty normal for a 290..

    Now not recommend by me but this comes from someone with way more experience then I " ultimately, your trying to IMPROVE the flow of the muffler. If the INLET of the muffler is 800 cubic mm, and the outlet of the muffler is 100 cu mm, there's an OBVIOUS restriction... try and land your outlet size close to 80% or so of exhaust port (at the cylinder wall) size... you can go up to 100% if your still using the spark screen..."

    As for the 046 running a 3/4 inch port I bet if I measure the hole in my dp and the factory holes on the side it will be well over 3/4 inch and that is all factory no mods by me... Now I know you got one of those expensive modded muffs but I would be willing to bet it could be opened a little more...


    O and I was a BIG fan of Savinelli back in my smoking days.......I got a alligator that I loved....[/quote

    Ahhh then my 120 anni is a big prize its fricken sweeet. Need money selling it and a dunhill (Both are worth well over 275.00).....Breaks my heart but I have another dozen. 14 on a two week rotation if you will.
  3. OhioBurner©

    OhioBurner© Minister of Fire

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    I was thinking I read 20-30% figure somewhere, that is 20-30% larger than the exhaust port (think 120%). Infact on that other site, there seemed to be a couple of folks saying to remove the whole recessed area. In any case, I think I'll start with just the 7/16" and can always go larger later.
  4. HittinSteel

    HittinSteel Minister of Fire

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    This saw ran awesome with this size hole

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  5. OhioBurner©

    OhioBurner© Minister of Fire

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    Ok mod completed. All my cameras are dead so no pics yet. Did a 7/16" hole in the depression then enlarged the opening of the 'bulge' up to the top bend. The limiter caps had me puzzled until I found a pic of what they look like then it made sense, got em out, shaved off the stop and stuck em back in. The whole tuning thing I'm not certain of. Think I got the low adjustment dialed in good but the high adjustment I'm not sure. As you richen it the speed drops and it starts to become raspy. But the speed starts dropping first, and the raspyness seems to come in gradually so I wasnt sure at what point to leave it. The idle speed seems to be fine, clutch is free, but trying to adjust it I couldnt get it to change? Maybe I wasnt on the screw enough, idk, but seems fine as is. I'll find out in the morning if I can feel any difference.
  6. ikessky

    ikessky Minister of Fire

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  7. OhioBurner©

    OhioBurner© Minister of Fire

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    Yeah I have seen several links to sound files... unfortunately no speakers! lol. I forgot to bring my laptop with me (up to the inlaws farm for the weekend) so I'll listen to em when I get back. I tweaked the saw just a bit more after cutting up the first tree this morning, and so far its running noticably better, of course I also have a sharper chain than I have before too. Weird thing is wasnt as loud as I thought it would be. But I got a new helmet/face screen/ear muff thingy so wearing ear protection anyways.
  8. smokinj

    smokinj Minister of Fire

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    You can tack them if you cant hear whats up on the sound wave
  9. Exmasonite

    Exmasonite Feeling the Heat

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    Any advice on where to find a decent tach? Having trouble on the old interwebs. Found this on ebay:

    http://cgi.ebay.com/ebaymotors/Digi...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

    Stihl website has what looked like "wired" ones but interested in the wireless one mentioned on Madsen's site.

    Don't really trust the ears and don't want to risk the ears, at least on the high speed. Spend too much time with a stethoscope in the ears and hearing loss would be devastating for me professionally.
  10. smokinj

    smokinj Minister of Fire

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    You can find them cheaper. Just make sure its rated for 2 cycle.
  11. Exmasonite

    Exmasonite Feeling the Heat

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    any good examples or recommendations, jay? wired vs wireless thoughts? wireless seem nice and easy
  12. HittinSteel

    HittinSteel Minister of Fire

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