ArboristSite.com Sponsors
 
 


Wierd carb problem on 394

Discussion in 'Chainsaw' started by parrisw, Mar 9, 2009.

  1. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    Ok, I rebuild a 394 a couple months ago with a good used P&C, just finally got around to rebuilding the carb and getting it running.

    It seems like its running crazy rich, so I leaned it out, still sounds rich, to my surprise, when I checked where the needle was the H needle was all the way in tight???? It idle's fine, so it seems like it doesn't have an air leak. Wierd thing, the saw when I got it was toast P&C was about the worst I've ever seen from lean seizure, I check the carb to see what it was set to and found the H needle was only open 1/3 a turn???? So I figured that was the issue, and one of the guy that was cutting with him said the saw was screaming crazy fast, I figured he just leaned it way out and killed it. If I set H needle to 1 1/4 open, it just run way rich, thats where my other 394 runs is just over 1 turn, stock with modded mufflers on both. I suppose I should just swap carbs and see if it fixes it???/

    any ideas?
     
  2. ZeroJunk

    ZeroJunk Addicted to ArboristSite

    Joined:
    Mar 1, 2008
    Messages:
    5,032
    Likes Received:
    603
    Location:
    Browns Summit NC
    I was working on a little 009L the other day and the high speed jet needle had a tight spot so bad that I thought it was bottomed out and it still had two turns to go. I don't know a good way to check that without damaging the needle if it is tight already. When you bottom the high and low are they the same height?
     
  3. BC_Logger

    BC_Logger AboristSite Guru

    Joined:
    Jan 22, 2007
    Messages:
    566
    Likes Received:
    105
    Location:
    BC .Candada
    The basic carburettor settings are

    H = 1 1/2 turns, L = 1 1/4 turns from seated

    you need to buy a tach to safely go further with tuning
     
  4. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    Yes, I have a tach, haven't tached it yet, but it's just not right, sounds way rich, I'll set it to 1.5 turns and tach it, and report back.
     
  5. Jacob J.

    Jacob J. Tree Freak

    Joined:
    Aug 26, 2001
    Messages:
    16,018
    Likes Received:
    3,682
    Location:
    Oregon
    It could be that some ham-fisted operator turned the high needle in too hard and damaged the seat. So now it's finicky and hard to keep in tune. I had a cutter do that to a new 044 magnum back in the mid-90's and the only fix was a brand new carb.
     
  6. Ghillie

    Ghillie Addicted to ArboristSite

    Joined:
    Jun 6, 2008
    Messages:
    1,550
    Likes Received:
    223
    Location:
    Central Ohio
    Did you pressure test the carb after rebuilding it?

    I agree with Jacob about a damaged needle and/or seat.
     
    Last edited: Mar 9, 2009
  7. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    I'll check that, the guy that tuned it last, didn't know what he was doing.

    I just reset the needles, H to 1.5 L to 1.25, tached it was reading 10,200 and lots of burble, richen H to 1.25 picked up to 11,500 and still burbleing allot. I'm afraid to go much richer, don't want to screw it up, It ran with the needle closed last time. I'll swap to my known good 394 carb and see what happens.
     
  8. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    No I didn't pressure test it. I'll check the needle seat though.
     
  9. Ghillie

    Ghillie Addicted to ArboristSite

    Joined:
    Jun 6, 2008
    Messages:
    1,550
    Likes Received:
    223
    Location:
    Central Ohio
    It won't diagnose the needle/seat being damaged but it may point you to another problem not thought of.

    I wish I could find diagrams of the circuits on that carb. I know I have them somewhere.
     
  10. lovetheoutdoors

    lovetheoutdoors Addicted to ArboristSite

    Joined:
    Feb 2, 2006
    Messages:
    1,459
    Likes Received:
    72
    Location:
    nc
    isnt 11,500 rpm about right on the 394's? i dont have a tach but plan on getting one.
     
  11. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    No. 12,500 is spec.
     
  12. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    Ya, I'm just going to stick my other carb on this saw. my other 394 is tore down anyway.
     
  13. rupedoggy

    rupedoggy Addicted to ArboristSite

    Joined:
    Jun 13, 2001
    Messages:
    1,879
    Likes Received:
    255
    Location:
    Placerville, Ca.
    Your needle lever is too high or the diaphram tip isn't tucked into the fork. Mike
     
  14. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    checked that twice. all seems good.
     
  15. Ghillie

    Ghillie Addicted to ArboristSite

    Joined:
    Jun 6, 2008
    Messages:
    1,550
    Likes Received:
    223
    Location:
    Central Ohio
    Is it a new needle? Not second guessing your work. Sometimes the simple things bite me in the arse.
     
  16. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    yes
     
  17. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    Finally got a chance today to swap the carbs, and yes, it was the carb?? Runs fine with the other carb. Anything to look for in the old carb? I did just rebuild it. I've taken it apart 3 times checking it over to make sure I didn't do it wrong. Everything is in the correct order. I haven't checked the needles yet though for damage.
     
  18. pioneerguy600

    pioneerguy600 Tree Freak

    Joined:
    Dec 23, 2007
    Messages:
    29,600
    Likes Received:
    4,159
    Location:
    N.S. Canada
    It sure is good to have 2 of everything when trying to diagnose problems like carbs and electronic ignitions, coils etc. Glad you narrowed it down to one bad carb. I also did some work this weekend on two 394`s, actually made one runner out of two parts saws, man have I got to tear down the runner to see what was done to it previously, its one aggressive beast. It beats the h-ll out of the Jonsred 2094 that I`ve got, the Jonsey is stock and its evident this 3094 is not.
    Pioneerguy600
     
  19. parrisw

    parrisw Tree Freak

    Joined:
    Jan 17, 2007
    Messages:
    13,798
    Likes Received:
    1,078
    Location:
    British Columbia, Canada
    I've found stock, they are real runners!!!
     
  20. pioneerguy600

    pioneerguy600 Tree Freak

    Joined:
    Dec 23, 2007
    Messages:
    29,600
    Likes Received:
    4,159
    Location:
    N.S. Canada
    I know a stock saw when I hear and run it and this one is definitely not, a tear down will tell the story.
    Pioneerguy600
     

Share This Page