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372 chain tension problem

Discussion in 'Chainsaw' started by ThackMan, Jan 8, 2019.

  1. CR888

    CR888 Addicted to ArboristSite

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    Yeah I'd order a few. A worn out $3 sprocket can damage expensive chains in short order.
    That sprocket was well past its service life.
     
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  2. vortec325

    vortec325 ArboristSite Operative

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    Wouldn’t you want to take a dial indicator and check the crank ? When the clutch engages won’t the leading edge hit first and cause that part of the clutch to have more wear than the rest . Causing it to look out of round ?


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  3. grizz55chev

    grizz55chev Tree Freak

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    If you can see it without a dial indicator why bother. If it’s not visible but you have chain issues or a vibration, then yes.
     
  4. vortec325

    vortec325 ArboristSite Operative

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    What I was kinda trying to say is couldn’t the clutch wear give a fake “bent” look . I couldn’t really see in the video with out zooming in full screen where I would condem the crank because it looked more like the pads on the clutch were kinda worn out of round


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  5. Mattyo

    Mattyo Youtube Speciawist

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    Never seen a clutch worn that far out of round.

    The crank was indeed bent likely from over tight hot chain and then letting the saw cool. Best guess :)
     
  6. vortec325

    vortec325 ArboristSite Operative

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    Would you consider this bent ?




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  7. ThackMan

    ThackMan ArboristSite Operative

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    Anyone have a P/N for either the OEM or Oregon needle bearing for the clutch? 365/372 pre xtorq.


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  8. r1stgei

    r1stgei ArboristSite Operative

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    Had the same thing happening on my 460... IMG_4996.jpg

    New:OLD


    Changed the rim sprocket. :)
     
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  9. Mattyo

    Mattyo Youtube Speciawist

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    Looks pretty straight to me :)
     
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  10. vortec325

    vortec325 ArboristSite Operative

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    I guess you just got a better eye for it than I do . The way the clutch is shaped it looked like it was possibly bent so I put a dial indicator on the shaft . Run out of 0.001 . Guess I better get my eyes checked


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  11. ThackMan

    ThackMan ArboristSite Operative

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    That’s plenty straight enough.


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  12. Mattyo

    Mattyo Youtube Speciawist

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    Your crank looks quite straight there. Mine was wayyyyy out.
     
  13. rd35

    rd35 Just an average Joe's brother!!

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    My guess is the bottoms of the drive links are not consistent....which is never a problem unless they are hitting the drum spline and preventing the links form settling into the sprocket openings fully. If some of those drive links have flattened points on them then when those flattened points travel around the sprocket the chain will temporarily get loose! A new rim should definitely fix this problem!
     
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  14. Mattyo

    Mattyo Youtube Speciawist

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    Very interesting point....at some point on the chain the links are bottoming out on that sprocket where other times they are not causing an inconsistency.

    I learned something! Thanks!
     
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  15. ThackMan

    ThackMan ArboristSite Operative

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    Put a new Oregon rim on the saw. No more problems. Thanks everyone.


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  16. Robin Wood

    Robin Wood Go hard or go home

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    how to identify worn rivet
     
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  17. ThackMan

    ThackMan ArboristSite Operative

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    Jeez that chain is done and it hasn’t even been sharpened down all the way.


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  18. Robin Wood

    Robin Wood Go hard or go home

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  19. Westboastfaller

    Westboastfaller Addicted to ArboristSite

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    The chain fits considerably looser on the bar as they cool. Its most importent to check tension after a short break for this reason or a high
    percentage of throws will accure within rhe first few minutes of start up.
    You may be on the right track. If say it was on the tight side, it does get tighter with the heat. Two factors that may create friction,, One being centripital force that's greater as RPM increases and the other when the cutters go into 'attack mode'
    Both tighten the chain against the bar, one as an inward force and the other as the cutters rocks back on the heal shortening the chain with a pull and release. The greater the hook and the lower the rakers then the greater the disturbance. So you have a constant pull and release on a tightening chain.

    That's one theory yes.

    Commonly with new bars and chains on a chain throw the drivers will mushroom over. So you loosen the chain and sometimes
    to 2" belly sag. When you throttle up, so then where does the slack go? It would concave between the the bar and sprocket.
    So that's the buffer on a properly adjusted chain, it will has a concave slack to take the disturbance from the bottom end.

    Another theory that could be related.
    The greatest pressure is at the drive end as it's the smallest sprocket. The least at the middle.
    Also you only have max three drivers at play on a 7T at any time and if you ran a hard chunk through the back of it then it may lift the previous pulling driver and that would be of the worst kind of pull to the crank

    Some Fallers think when a big cut closes?No that's also what's hard on bottom ends though.

    I've had it happen once in 30,000 saw hours.
    and I don't run tight chains.

    A couple of questions for you: Do you see this much ?
    Also this was a new 2010,, 2165 BB ported.
    Saw seemed lite compared to all my 372.
    Is the crank the same as 365/372?
    20 yrs with 371/375/372 and never a problem.
    A short time with one Jonsered and I get a bent
    crank.[/QUOTE]
     
  20. HarleyT

    HarleyT Tree Freak

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    Wow! This was post #2!!!
     
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