In loving memory of Kenis D. Keathley 6/4/81 - 3/27/22 Loving father, husband, brother, friend and firewood hoarder Rest in peace, Dexterday

391 overhaul advice?

Discussion in 'Chainsaws and Power Equipment' started by lotifoazurri, Mar 9, 2020.

  1. lotifoazurri

    lotifoazurri

    Joined:
    Dec 30, 2018
    Messages:
    31
    Likes Received:
    189
    Location:
    SC
    I have a very used 391 (older finned cylinder) that needs a new piston and cylinder - I bought it as a parts saw basically knowing it would need some love to run again.

    What else would y'all recommend replacing at the same time that I do the tear-down to replace them?

    I am new to this world of chainsaw repair and could use some advice from the experts.
     
  2. cnice_37

    cnice_37

    Joined:
    Oct 4, 2013
    Messages:
    3,205
    Likes Received:
    14,192
    Location:
    SE Mass
    Oh boy, that's not an easy saw to start with!

    Crank seals
     
  3. buzz-saw

    buzz-saw

    Joined:
    Jan 31, 2020
    Messages:
    3,995
    Likes Received:
    22,921
    Location:
    Ct.
    ^^^^^^^^^^x2^^^^^^^^^^^
     
  4. The Wood Wolverine

    The Wood Wolverine

    Joined:
    Aug 23, 2015
    Messages:
    15,673
    Likes Received:
    96,542
    Location:
    Gettysburg, PA
    ^^^x3^^^
    Crank seals, fuel line and filter, carb rebuild kit,
     
  5. M2theB

    M2theB

    Joined:
    Jan 13, 2017
    Messages:
    2,989
    Likes Received:
    19,074
    Location:
    Central Massachusetts
    X4 on the seals

    Impulse line while your at it.

    Take pictures!

    Just did an 029 to 039 conversion. These are a Rubic's cube.

    But fun.
     
  6. AJtree88

    AJtree88

    Joined:
    May 15, 2014
    Messages:
    318
    Likes Received:
    1,764
    Hopefully the price on the piston and cylinder have come down. Stihl was mighty proud of them last time I checked. Definitely overhaul the fuel system while you have it apart.
     
  7. Nixon

    Nixon

    Joined:
    Oct 4, 2013
    Messages:
    669
    Likes Received:
    3,009
    Location:
    West Sunbury,Pa .
    The price for the OEM P&C is still quite high 300 + . there are some AM P&C kit starting to show up . They vary from 140- 190+ . I’ve got a fried 311 here that needs a new P&C . But all the AM kits have the three bolt intake block ,and this 311 has the 4 bolt intake . I’m tempted to find a used 3 bolt lock and try an AM kit .
     
    metalcuttr, tamarack and M2theB like this.
  8. lotifoazurri

    lotifoazurri

    Joined:
    Dec 30, 2018
    Messages:
    31
    Likes Received:
    189
    Location:
    SC
    Thanks y'all.

    I'm not new to wrenching - I spent ten years working on bikes and air cooled VWs so I'm not a total noob.

    From what I see the piston/cylinder for this is the 1140 020 1204.

    For the seals, there are two that seem to be indicated and I am not sure which is correct for this one: either 9639 003 1585 or 9638 003 1581.

    Anybody know the difference or how to tell which one is correct for this saw?
     
  9. Mtnbikerfred

    Mtnbikerfred

    Joined:
    Jun 19, 2019
    Messages:
    69
    Likes Received:
    518
    Location:
    Svenson, Or
    Y'know what? Go for it. Tear it down and see what it actually needs. You'll probably be able to ID or at least measure the seals.

    Let's see it on the healing bench!!!
     
    metalcuttr and T.Jeff Veal like this.
  10. T.Jeff Veal

    T.Jeff Veal

    Joined:
    Oct 8, 2015
    Messages:
    22,286
    Likes Received:
    134,641
    Location:
    Country life, Ga
    Port and MM while you're at it. Pop up piston...
     
    MAF143 and metalcuttr like this.
  11. cnice_37

    cnice_37

    Joined:
    Oct 4, 2013
    Messages:
    3,205
    Likes Received:
    14,192
    Location:
    SE Mass
    I think you want 1585, the blue guys. I believe the others are for when you don't want to tear it down completely and replace with the crank still in place.
     
  12. M2theB

    M2theB

    Joined:
    Jan 13, 2017
    Messages:
    2,989
    Likes Received:
    19,074
    Location:
    Central Massachusetts
    I think that’s a clam shell design. Once you peel the saw apart and lift the jug, crank pulls right out, as long as the clutch and flywheel are off, needed to change seals anyway.
     
    T.Jeff Veal and metalcuttr like this.
  13. cnice_37

    cnice_37

    Joined:
    Oct 4, 2013
    Messages:
    3,205
    Likes Received:
    14,192
    Location:
    SE Mass
    Yup, clamshell. I thought if you don't do a full teardown, you can still replace seals with crank and cylinder in place. Thus, the other p/n. ? Never done out that way myself.
     
    T.Jeff Veal and M2theB like this.
  14. M2theB

    M2theB

    Joined:
    Jan 13, 2017
    Messages:
    2,989
    Likes Received:
    19,074
    Location:
    Central Massachusetts
    Not sure that you can.
    There’s a cast lip outboard of the seal on the flywheel side anyway.
    I’ve only done a few Stihl clam shells and on those it looks like that is the path.
    The seals don’t have the tin shroud to drive it into the annular space. They seem to rely on setting them in the lower half pocket and the compressing them when you set the jug.
     
    cnice_37 and T.Jeff Veal like this.
  15. M2theB

    M2theB

    Joined:
    Jan 13, 2017
    Messages:
    2,989
    Likes Received:
    19,074
    Location:
    Central Massachusetts
    5F3E4859-079D-4C1B-8BD5-9824F95924A6.png You’ll have zoom in a little, but I think this shows it
     

    Attached Files:

  16. cnice_37

    cnice_37

    Joined:
    Oct 4, 2013
    Messages:
    3,205
    Likes Received:
    14,192
    Location:
    SE Mass
    T.Jeff Veal likes this.