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Early Failure - Zama Metering Diaphragm?

Discussion in 'Chainsaw' started by SteveSr, Nov 16, 2019.

  1. SteveSr

    SteveSr Addicted to ArboristSite

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    I had been noticing the smell of gasoline while working in the garage. Last week I decided to do the last mowing and trimming of the season. When I wen to start my FS85 weed trimmer It wouldn't run properly. Would only run pig rich at WOT and stall at idle and wouldn't restart until it cooled off.

    Carb failed the fuel input line pressure test. At first I suspected something stuck in the needle valve. When I tore into it I found that the metering diaphragm was stiff as cardboard! Problem found.

    However, this was a relatively new carb only a year or 2 old. The carb is a Zama C1Q-S157. I only use ethanol free fuel and drain the machine and run it dry over the winter storage. All of my other 2-stroke saws and tools have been using the same fuel without issues.

    This appears to be a Zama materials / quality issue. Has anyone else seen early failures on replacement Zama carbs?
     
  2. hotshot

    hotshot ArboristSite Operative

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    You cut wood with that?

    Thought this forum was for chainsaws...
     
  3. SteveSr

    SteveSr Addicted to ArboristSite

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    Yes, with a circular saw blade!

    Shhhhh.... I won't tell if you won't! Not the first and won't be the last to post about other 2-stroke tools. Also a lot of saws have Zama carbs on them as well.
     
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  4. MaddBomber

    MaddBomber ArboristSite Operative

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    My '98 JRed 2065 has a Zama. No issues with it. It handles a 75cc big bore fine.
    I don't know if they've downgraded quality for better profits, as all companies seem to be doing lately.
    Are you using ethanol gas? That can really mess up small carbs.... and everything they're bolted to.
     
  5. HarleyT

    HarleyT Tree Freak

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    Where did you get the carb?
     
  6. HarleyT

    HarleyT Tree Freak

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    Amazon cheapo?
     
  7. SteveSr

    SteveSr Addicted to ArboristSite

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    Official Stihl from a Stihl dealer.
     
  8. SteveSr

    SteveSr Addicted to ArboristSite

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    E-Free as noted in original post.
     
  9. DND 9000

    DND 9000 ArboristSite Guru

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    That C1Q-S157 carburetor was introduced in 2009. At that time the material of the diaphragms was not already changed as far as I now. The pump piston with it`s components was changed on that carburetor and the sealing ring of the accelerator pump was made of NBR (neoprene) now.

    There was a change in the material of the metering diaphragm in 2016. For example: The material for the metering diaphragm on Zama C1Q carburetors used on the MS 271, 291 was changed. I also think this change is valid for other models from that date on.
     
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  10. SteveSr

    SteveSr Addicted to ArboristSite

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    Thanks for the info. I suspect that this is a post 2016 carb. Is there any way to know by looking at the old diaphragm? In any case I am using E-Free gas so it really ashouldn't matter. I was just really surprised to have one die so young after being properly cared for. Makes me suspicious that Zama doesn't have a good handle on their supply chain.
     
  11. DND 9000

    DND 9000 ArboristSite Guru

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    No I don`t know a way to identify by looking at it if it is a new or older diaphragm material.
     
  12. Brent Nowell

    Brent Nowell ArboristSite Guru

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    It is quite possible that the fuel you were using last maybe had ethanol in it. I know it dries nylon/rubber fast when sitting.
    Did the fuel come out of a can or was it at the pump?

    I only ask cause gas stations that used to be ethanol free seem to be converting without informing their customers.
    I have used quite a few zama based carbs and have not seen this happen in just one season with my equipment.
     
  13. SteveSr

    SteveSr Addicted to ArboristSite

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    The fuel came out of a dedicated E-Free dispenser at a local gas station. It should have been E-free. Of course, there is nothing to stop the distributor from dropping the wrong product into the wrong underground tank. Haven't had this issue with any of my other equipment either (yet?).

    I haven't either so I thought that I would ask.
     
  14. SteveSr

    SteveSr Addicted to ArboristSite

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    I went to look and the date code on the affected carb is 549A. Anybody know how to decode a Zama date code?
     
  15. DND 9000

    DND 9000 ArboristSite Guru

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    Date code 549A means that this carburetor was produced in 2015 (49th week) in the A shift.
     

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