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What did I do wrong? Scored 490

Discussion in 'Chainsaws' started by Nutball, Feb 26, 2019.

  1. Nutball

    Nutball Super OPE Member

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    So, my 490 started out likely as a home depot return I got from a refurbisher for cheap. It looked nearly new, linear marks in the cylinder were few and couldn't be felt: they were just polished lines. After a port job and a thorough cleaning to ensure metal dust is removed, and 9 15" cookies later I take it apart since I used the wrong gasket maker and noticed the stuff liquefying. The saw ran very well the whole time. After I took it a part I notice many scratches in the cylinder that I can feel with my finger nail. WTH? Assembled with plenty of Benol... lots of it to avoid extreme initial wear from any left over metal dust. 40:1 fuel used.

    The scoring seems pretty even around the cylinder, so the ring ends or ports don't seem to be the problem.

    DSC00673 (1280x929).jpg DSC00674 (1280x661).jpg DSC00675 (1280x1157).jpg DSC00676 (1280x1260).jpg DSC00677 (1280x591).jpg

    Guess I'll run it on 32:1 for the rest of it's life. I don't think new rings would be worth it would it?

    EDIT: I just remembered when cutting cookies, on the 4rth or 5th in a row it seemed to loose a little power as if it was an old wore out saw getting hot. It didn't loose much though, and the cut times were only getting faster.
     
  2. fearofpavement

    fearofpavement Pinnacle OPE Member

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    That damage is the result of a foreign object in the cylinder. ie, a piece of metal, perhaps an ear from a circlip, a piston ring locating pin or something like that. It's not typical scoring that results from insufficient oil or overheat. I see your pins are in place, check the circlips.
     
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  3. Nutball

    Nutball Super OPE Member

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    Earless clips were used, they are fine. To me the wear seems very even and as if I ran it in sandy wood without an air filter, both of which isn't true.
     
  4. mettee

    mettee Pinnacle OPE Member

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    I'm looking at your ports, there is zero radius on them.

    The intake and exhaust look sharp. The transfers look like they might be radiussed
     
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  5. Nutball

    Nutball Super OPE Member

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    Echo ports are very sharp when new. I put a very heavy polish on them (polished a chamfer) it feels very smooth and round to the touch, yet an extremely small radius. I did point out that the scoring happens evenly regardless of port location. I tend to see on echo saws that much scoring happens above only the ports as they are sharp when stock.
     
  6. mettee

    mettee Pinnacle OPE Member

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    If it hangs a ring, and pulls off material from the cylinder wall that material is not localized in one spot at 10k rpm with the velocity it's seeing internally.

    They just look sharp to me. Being sharp from the factory doesn't seem like it's good to me.

    Some one else will chime in, don't take my word as anything. Just what it looks like.
     
  7. Deets066

    Deets066 AKA Deetsey

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    Do you have a video of you cutting with it?
     
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  8. David Young

    David Young Safety First !!!!!! Staff Member

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    No chamfer...

    Next!
     
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  9. Nutball

    Nutball Super OPE Member

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    I'm usually pretty shrewd in figuring limits and what things require, but I guess I came a little too close to the limit on this one. I see now with a magnifier how I could have chamfered much better. I also figured round and smooth to the touch as well as having the rings easily slide over the ports when first assembled was a sign that all is good.

    I'm not saying the chamfer is the definite cause, but it could be. The damage is just so minimal, but thanks for helping me take a 3rd and closer look at it.

    It starts going weak on the 3rd cut, so I tweak the carb a bit and it makes its fastest 2 cuts after that.

     
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  10. Nutball

    Nutball Super OPE Member

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    I figure a ball burr with a straight tool would be the easiest way to chamfer? That or a small 45 degree tool.
     
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  11. mettee

    mettee Pinnacle OPE Member

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    On a side note the porting looks good, just hit the corners more on the next piston and cylinder.

    There is a complete crank case on amazon for 180, not sure if its really there
     
  12. mettee

    mettee Pinnacle OPE Member

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    I use a small convoluted wheel or craytex, that way I dont jack up the cylinder. I savae my worn down ones for this op. After all the porting it is easy to touch off the cylinder wall with a burr.

    [​IMG]
     
  13. Nutball

    Nutball Super OPE Member

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    Yea, those are my favorite.

    There's 2 complete NIB saws near me for $200. I may or may not pick them up soon.
     
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  14. Duane(Pa)

    Duane(Pa) It's the chain...

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    Just a thought. If you are hitting a rev limiter and not four stroking, it may be lean? IDK if you got it clean enough.
     
    Last edited: Feb 26, 2019
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  15. Nutball

    Nutball Super OPE Member

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    It wasn't hitting the rev limiter.
     
  16. David Young

    David Young Safety First !!!!!! Staff Member

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    i'd recommend a stone for chamfering, put up the burs the finer the stone the better. becareful that you dont lift the plating when done use a scotchbrite on a mandrel or fine dremel flap wheel then feel with your fingers for any remotely sharp spots. finishing touches with sand paper on a finger tip.

    clean up hot soapy water. carb/brake cleaner works well and will break down carbon. Make sure you have exam gloves on so the solvent doesn't get into your skin.
     
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  17. dahmer

    dahmer Pinnacle OPE Member

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    Lightly drag a cotton ball across any surface you hit with the grinder. The fibers of the cotton ball will snag on any imperfections that even your fingers can’t feel.
     
  18. Deets066

    Deets066 AKA Deetsey

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    Blue ceramic ball works good. As David said a stone is the way to go
     
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  19. Nutball

    Nutball Super OPE Member

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    What about the tight corners Echo uses for their square transfers?

    I mixed up a couple gallons of 32:1. I'll chamfer the ports, and see how long it lasts. Still can't decide if it would be best to try a new ring to wear into the cylinder or just use the same
     
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  20. 00wyk

    00wyk Pinnacle OPE Member

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    A foreign object like liquified gasket perhaps...

    ...After a port job and a thorough cleaning to ensure metal dust is removed, and 9 15" cookies later I take it apart since I used the wrong gasket maker and noticed the stuff liquefying.
     
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