ArboristSite.com Sponsors
 
 


dolmar 6400/7900 big bore kits. how are they holding up?

Discussion in 'Chainsaw' started by Mac 6-10, Nov 8, 2013.

  1. Mastermind

    Mastermind Work Saw Specialist

    Joined:
    Nov 21, 2009
    Messages:
    32,601
    Likes Received:
    19,773
    Location:
    Tennessee
    Then top of the piston being up in the port is no problem. 80% of the exhaust flow happens when the port first cracks open anyway. I'll use the thin gasket, or none at all if there wasn't a squish clearance issue.
     
  2. Trzebs13

    Trzebs13 ArboristSite Member

    Joined:
    Oct 26, 2010
    Messages:
    58
    Likes Received:
    19
    Location:
    Central WI
    OK, that makes sence but dosent seem totaly right. I measured the spacer and its actually about .061" thick and got a piece of thicker solder and the squish measured .093" so with no gasket it would be .032". Still seems big to me. But I'm guessing that the added compression would far out way the piston no clearing the entier port.
     
  3. Mac 6-10

    Mac 6-10 AboristSite Guru

    Joined:
    Feb 1, 2013
    Messages:
    547
    Likes Received:
    227
    Location:
    Missouri
    These kits also fit a solo saw that has a 1 mm longer stroke. That is why your kit came with that thick spacer. Run it no base gasket (double check you'd squish) and go cut wood. That's what I did and haven't looked back!
     
  4. nmurph

    nmurph ArboristSite.com Sponsor

    Joined:
    Nov 26, 2007
    Messages:
    14,996
    Likes Received:
    4,859
    Location:
    Somewhere in the space-time continuum
    You also need to check the top of the bore. Some of these BB kits aren't plated all the way to the corner---> black ring of death. As long as you are running a base gasket you are ok. But if the gasket is removed the ring will end up on the unplated area.
     
  5. blsnelling

    blsnelling Site Sponsor

    Joined:
    Nov 8, 2006
    Messages:
    43,876
    Likes Received:
    8,625
    Location:
    Franklin, OH
    As mentioned above, that spacer is not for your saw. Pitch it.
     
  6. watsonr

    watsonr Aftermarket Parts Pusher

    Joined:
    Jan 3, 2010
    Messages:
    6,774
    Likes Received:
    1,589
    Location:
    Started in Idaho, ended up in Virginia!
    Not that the aluminum can't take the heat generated by combustion, the aluminum can't take the ring rubbing it.
     
  7. Trzebs13

    Trzebs13 ArboristSite Member

    Joined:
    Oct 26, 2010
    Messages:
    58
    Likes Received:
    19
    Location:
    Central WI
    Yes I did notice that, I did start it so I should be able to see a line where the rings were coming up to and get a measurement on it to make sure.
     
  8. Trzebs13

    Trzebs13 ArboristSite Member

    Joined:
    Oct 26, 2010
    Messages:
    58
    Likes Received:
    19
    Location:
    Central WI
    photo 2.JPG photo 1.JPG

    As far as the Muffler goes, should a guy just remove the inner baffle with the Cat in it and open up the existing outlet and call'r a day?
     
  9. Mac 6-10

    Mac 6-10 AboristSite Guru

    Joined:
    Feb 1, 2013
    Messages:
    547
    Likes Received:
    227
    Location:
    Missouri
    I did the same thing you did with the muffler. But I left only the shell.
     
  10. madhatte

    madhatte It's The Water

    Joined:
    Apr 19, 2009
    Messages:
    5,120
    Likes Received:
    1,163
    Location:
    Puget Sound
    My BB has been running since early '10 with no troubles. I wish I could say the same about the chintzy plastic flange that couples the carb to the boot, though. Be careful not to over-tighten the thing or it will spin the nuts in their keeper. So far that's my only real complaint about these saws, and that only because of the risk of an air leak. Oh, and of course, there's still no real dealer network.
     
  11. nmurph

    nmurph ArboristSite.com Sponsor

    Joined:
    Nov 26, 2007
    Messages:
    14,996
    Likes Received:
    4,859
    Location:
    Somewhere in the space-time continuum
    Not only can you spin the nut, but you can also deflect the manifold and cause it not to seal. I had one recently that gave me fits finding the source of the air leak until I pulled the carb and checked it over carefully.
     
  12. Trzebs13

    Trzebs13 ArboristSite Member

    Joined:
    Oct 26, 2010
    Messages:
    58
    Likes Received:
    19
    Location:
    Central WI
    What kind of RPM's are you guy's running yours at?
     
  13. watsonr

    watsonr Aftermarket Parts Pusher

    Joined:
    Jan 3, 2010
    Messages:
    6,774
    Likes Received:
    1,589
    Location:
    Started in Idaho, ended up in Virginia!
    I'd need to take a tach to the pile... maybe tomorrow. I have one here with a 32" bar and two tanks thru it. Was going to be put to mill duty but the buyer decided that a 2100CD would be a better option.
     
  14. ClassicSWC

    ClassicSWC ArboristSite Lurker

    Joined:
    Feb 27, 2012
    Messages:
    43
    Likes Received:
    10
    Location:
    York, Pa
    I've been following these threads because I have an interest in bumping up my 6400. It seems that the 84cc bbk isn't as strong as the 79cc oem. If that's correct, what's the reason for that? Is one easier to tune that the other? Just curious about learning a little. Thanks
     
  15. nmurph

    nmurph ArboristSite.com Sponsor

    Joined:
    Nov 26, 2007
    Messages:
    14,996
    Likes Received:
    4,859
    Location:
    Somewhere in the space-time continuum
    The BB kits have very narrow transfer tunnels. You increase the displacement but it can't breathe to take advantage of it.
     
  16. Mac 6-10

    Mac 6-10 AboristSite Guru

    Joined:
    Feb 1, 2013
    Messages:
    547
    Likes Received:
    227
    Location:
    Missouri
  17. nmurph

    nmurph ArboristSite.com Sponsor

    Joined:
    Nov 26, 2007
    Messages:
    14,996
    Likes Received:
    4,859
    Location:
    Somewhere in the space-time continuum
    They are pretty close to OEM in terms of power.
     
    Stephen C. likes this.
  18. Trzebs13

    Trzebs13 ArboristSite Member

    Joined:
    Oct 26, 2010
    Messages:
    58
    Likes Received:
    19
    Location:
    Central WI
    So if you were to get in there and open up the transfers you think that it would preform that much better? Now granted not easy to do but not impossible.
     

Share This Page