ArboristSite.com Sponsors
 
 


Do you have to check ring end gap? assembly questions HELP!!

Discussion in 'Chainsaw' started by cbr929rr, Mar 13, 2008.

  1. cbr929rr

    cbr929rr ArboristSite Member

    Joined:
    Apr 9, 2007
    Messages:
    53
    Likes Received:
    2
    Location:
    rhode island
    I ordered a 7900 conversion for my makita 6401. I have never work on a 2 stroke before but have a little experience with 4 stroke atv's and very rarely leave anything stock, its been a problem for years.

    1. When I assemble the piston/cylinder do you have to check ring end gap. I don't think you could because the head is not removable like on a four stroke?

    2. I dont have a ring compressor can I use a zip tie or any other makeshift idea's you have done?

    3. I am not going to woods port because I don't know how to use a degree wheel and I have read the 7900 doesn't always respond well to mods like husky and stihl. But could I just clean up the ports from casting imperfections and maybe explain how to widen ports or just leave well enough alone, or if anyone would be interested in me sending them the cylinder for minor mods, I have it muffler modded already.:dizzy:

    4. I already have a tach and can tune the carb pretty well after the muffler mod.:chainsaw:

    5. What if any other tips would you recomend for a first timer who is somewhat worried about screwing up his saw. ex. leave a rag around the lower end incase a clip fall in?
     
  2. Tzed250

    Tzed250 Account Hold

    Joined:
    Jul 23, 2002
    Messages:
    7,030
    Likes Received:
    1,053
    Location:
    West Virginia
    I always check it...

    Put the ring only in the bore, then square it with the piston, check the gap.

    I have not needed a ring compressor for a saw.

    With the circlips, eye protection is more important than the rag.

    You can do it!!!
     
    Last edited: Mar 13, 2008
    timberwolf likes this.
  3. sawinredneck

    sawinredneck Addicted to ArboristSite

    Joined:
    Mar 3, 2006
    Messages:
    9,508
    Likes Received:
    1,370
    Location:
    Kansas
    Nice and slow here:

    1) You should, just slide the ring/rings up from the bottom, square it with the piston and measure. It's no different than a car, just from the bottom.

    2)I use two small flat screwdrivers and my thumb. There is usually a slight bevel on the bottom of the cylinder that makes it a lot easier. Sometimes you can "cock" the cylinder to one side then the other side will go in fairley easy.
    The hardest part it lack of room.

    3)You don't need a degree wheel for mino mods. Clean out the flashing, blend everything and polishing will help a lot. Widdening the ports will not change timing, just allow more flow through it. (It's just an air pump, remeber that) Just make sure you bevel everything on the inside of the cylinder so you don't tear the ring off the piston.

    4) Good to know.

    5) Take you're time. It's really not that hard. Once you get in and do it once or twice you will laugh at being so scared about it!!

    It's an air pump, not rocket science!! Have some fun!
     
  4. cbr929rr

    cbr929rr ArboristSite Member

    Joined:
    Apr 9, 2007
    Messages:
    53
    Likes Received:
    2
    Location:
    rhode island
    Do you use any sealer with the base gasket or glue like idian head shellac?

    I know i'm forgetting other questions but I will keep thinking before my hands get dirty!
     
  5. lesorubcheek

    lesorubcheek Addicted to ArboristSite

    Joined:
    Jan 19, 2005
    Messages:
    1,658
    Likes Received:
    251
    Location:
    Florida
    To check the ring end gap, remove the rings from the piston. Compress (fingers work here) and insert the rings (one at a time is OK) into the cylinder. Insert the piston behind the ring and push it in a few inches until you feel comfortable that its sitting squarely in the cylinder. Be careful not to push too far and catch a ring gap on a port edge. Pull the piston out and then you can check the gap on the ring.

    Dan
     
  6. cbr929rr

    cbr929rr ArboristSite Member

    Joined:
    Apr 9, 2007
    Messages:
    53
    Likes Received:
    2
    Location:
    rhode island
    maybe I will practice on the 6401 jug blending, its in fine shape but I would rather mess up the old jug its only going to be a spare and collect dust.

    I should also lube the piston, pin and cylinder with straight 2 stroke oil too Right?
     
  7. bcorradi

    bcorradi Arboristsite.com Sponsor

    Joined:
    Jan 18, 2004
    Messages:
    4,264
    Likes Received:
    585
    Location:
    Lake Park, MN
    I got by without using a ring compressor for a few years, but after making the minimal investment in one I wish I had done it sooner.

    However if you don't want to invest in one...put the piston in the cylinder before attaching the piston to the crank. It makes life a bit easier.
     
  8. sawinredneck

    sawinredneck Addicted to ArboristSite

    Joined:
    Mar 3, 2006
    Messages:
    9,508
    Likes Received:
    1,370
    Location:
    Kansas
    If you are using the stock base gasket, no sealer is needed. If you don't want to use the gasket to up the compression you will need a sealant. Use an Anerobic sealeant, it will stay pliable and the fuel wont affect it. Loc-Tite makes some and you can get it at O'Rielly's easily.
     
  9. bcorradi

    bcorradi Arboristsite.com Sponsor

    Joined:
    Jan 18, 2004
    Messages:
    4,264
    Likes Received:
    585
    Location:
    Lake Park, MN
    No sealer on the base gasket is needed...install it dry. Yes applying a thin film of 2 cycle on the parts is a good idea.
     
  10. bcorradi

    bcorradi Arboristsite.com Sponsor

    Joined:
    Jan 18, 2004
    Messages:
    4,264
    Likes Received:
    585
    Location:
    Lake Park, MN
    If you are going without a base gasket like Andy aka sawinredneck mentioned make sure you have .020 squish clearance (space between the piston and the top of the jug) .
     
  11. sawinredneck

    sawinredneck Addicted to ArboristSite

    Joined:
    Mar 3, 2006
    Messages:
    9,508
    Likes Received:
    1,370
    Location:
    Kansas
    Have a hey day on that old jug!!!! Grind the piss out of it!!!

    Play a bit, find out what worked, then see when it drops out, there is youre base line for the new jug!!!

    I wash everything out with water, then rinse the crankcase out with two stroke mix.
     
  12. cbr929rr

    cbr929rr ArboristSite Member

    Joined:
    Apr 9, 2007
    Messages:
    53
    Likes Received:
    2
    Location:
    rhode island
    I have a dremel and an air grinder. I would probably feel more comfortable with a dremel have adjustable speeds.

    1. Should I use a stone, or the rubber wheel with 60grit of 120grit rolls of paper.

    2. And how do I bevel the inside of the jub at the ports so the ring will not snag?
     
  13. sawinredneck

    sawinredneck Addicted to ArboristSite

    Joined:
    Mar 3, 2006
    Messages:
    9,508
    Likes Received:
    1,370
    Location:
    Kansas
    You may have to get carbide to get through the coating. Then use stones and finish with the sandpaper.

    Reach in from the outside and point the tip at a 45ish degree angle to the bore.
     
  14. blsnelling

    blsnelling Site Sponsor

    Joined:
    Nov 8, 2006
    Messages:
    43,902
    Likes Received:
    8,670
    Location:
    Franklin, OH
    I use a Dremel with the Structured Carbide bits in the cylinder. And I use a high speed cutter on pistons. The chrome in the cylinder would detroy it though.
     
  15. cbr929rr

    cbr929rr ArboristSite Member

    Joined:
    Apr 9, 2007
    Messages:
    53
    Likes Received:
    2
    Location:
    rhode island
    Won't this effect timing and I would need to raise or lower the ports to get the timing correct? I think I might skip losing the base gasket.
     
  16. sawinredneck

    sawinredneck Addicted to ArboristSite

    Joined:
    Mar 3, 2006
    Messages:
    9,508
    Likes Received:
    1,370
    Location:
    Kansas
    That will not efect timing enought to even worry about!
     
  17. Mad Professor

    Mad Professor Addicted to ArboristSite

    Joined:
    Jul 2, 2007
    Messages:
    4,681
    Likes Received:
    626
    Location:
    North East USA
    A wooden support to hold the piston in place is handy when trying to get the Cyl on.
     
  18. cbr929rr

    cbr929rr ArboristSite Member

    Joined:
    Apr 9, 2007
    Messages:
    53
    Likes Received:
    2
    Location:
    rhode island
    how do you make the intake rough to create turbulence to mix (atomize) the air and gas mixture?
     
  19. Nofeargoneold

    Nofeargoneold ArboristSite Lurker

    Joined:
    Mar 13, 2008
    Messages:
    6
    Likes Received:
    0
    Location:
    Byron Center, MI
    Back to the circlips....I've found most recently cus I don't have all the pro tools, I used a 5/16 chain file and bent a little hook on the handle end to make the perfect tool to remove those stubborn circlips. just reach in there and pop the first side out and then start twisting the hook around the circlip till it pops out. Worked Great on my snowmobile pistons. No need to try on saws yet.
     

Share This Page