Husqvarna CCC Ebay Store DHS Online Store

ms 390 Tuning and tweaking

Discussion in 'Ask the Experts' started by justadirthauler, Apr 26, 2020.

  1. justadirthauler

    justadirthauler New OPE Member

    Joined:
    Apr 23, 2020
    Messages:
    4
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    71286
    Local Time:
    1:08 AM
    Hi all, I've got a 390, someone told me ya'll could tell me how to advance the timing and modify the muffler a bit. Most of the mods I've done in the past to various saws haven't changed them much in the big picture so I thought I'd ask some more knowledgeable heads this time.
     
  2. Lightning Performance

    Lightning Performance Here For The Long Haul!

    Joined:
    Jan 26, 2016
    Messages:
    6,512
    Likes Received:
    16,779
    Trophy Points:
    408
    Location:
    East of Philly
    Local Time:
    2:08 AM
    Search Google for threads on Outdoor Power Equipment Forum.

    Welcome
    Get the goo off it first inside and out. You can burn it off gently mind you. A good degreaser works also.

    Drill two holes under the deflector straight through the front baffle. It will be loud or drill around the baffle but under the cover. The square is the baffle face.
    Make damn sure you get out ALL the metal chips in the muffler. Soap and water with some pressure works well. Rinse and repeat.

    File 0.030 off the flywheel key.
    460 carb... maybe. It requires mods to work well.
    Study time.

    GL
     
  3. dmb2613

    dmb2613 Super OPE Member GoldMember

    I Support This Forum as a Gold Member!
    Joined:
    May 13, 2018
    Messages:
    287
    Likes Received:
    592
    Trophy Points:
    178
    Location:
    Randolph Virginia
    Local Time:
    2:08 AM
    440 carburetor is a direct bolt on , but the 390 carb will be fine just richen up the high side , you will need to make the hole larger on the deflector plate on the muffler also , it will run like a raped ape then the key is made to the flywheel make sure you file off the correct side of the key The flywheel will need to be rotated to the left, I take off about 1/4 of the width of the key , if it is too high don't worry just twist it back some it is a tapered fit and needs no key at all to run. I grind 2 slots in the muffler just connect the holes that are there and do the same to the top of the muffler some already have hole there I do this on a regular basis beware of everything you read , some just post without any experience, make sure you have the plate that goes behind the muffler if you put a pop up piston in it as it will run hotter.
     
    huskyboy likes this.
  4. dmb2613

    dmb2613 Super OPE Member GoldMember

    I Support This Forum as a Gold Member!
    Joined:
    May 13, 2018
    Messages:
    287
    Likes Received:
    592
    Trophy Points:
    178
    Location:
    Randolph Virginia
    Local Time:
    2:08 AM
    most I have typed since I was in school lol
     
    angelo c likes this.
  5. justadirthauler

    justadirthauler New OPE Member

    Joined:
    Apr 23, 2020
    Messages:
    4
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    71286
    Local Time:
    1:08 AM
    Thanks a lot! That definitely gives me something to go on.
     
  6. justadirthauler

    justadirthauler New OPE Member

    Joined:
    Apr 23, 2020
    Messages:
    4
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    71286
    Local Time:
    1:08 AM
    This popup piston, where would I go to find one?
    That's kind of what I've been looking for.
     
  7. dmb2613

    dmb2613 Super OPE Member GoldMember

    I Support This Forum as a Gold Member!
    Joined:
    May 13, 2018
    Messages:
    287
    Likes Received:
    592
    Trophy Points:
    178
    Location:
    Randolph Virginia
    Local Time:
    2:08 AM
    H L supply carries them
     
    huskyboy likes this.
  8. justadirthauler

    justadirthauler New OPE Member

    Joined:
    Apr 23, 2020
    Messages:
    4
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    71286
    Local Time:
    1:08 AM
    Ok thanks for all the info!
     
  9. Carhartt

    Carhartt Super OPE Member

    Joined:
    Aug 18, 2016
    Messages:
    586
    Likes Received:
    768
    Trophy Points:
    158
    Location:
    Central Pa
    Local Time:
    2:08 AM
    Isnt the intake rubber tube ID more restrictive than the ID of an oversized carb? I have never tried and could but never felt the need to replace the existing carb. Always thought they put out plenty of fuel if richened.
     
Loading...

Share This Page

Loading...
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice