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Stihl MS 170 throttle linkage keeps coming loose at carburator end

Discussion in 'Chainsaw' started by godfreydanials, Mar 31, 2012.

  1. godfreydanials

    godfreydanials New Member

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    I have a Stihl MS 170 that is about 4 years old, with very little useage. Recently the hooked end of the throttle linkage started popping out of the slotted lever on the carburator. I have reconnected it twice and it just popped out again. I don't see any retainers or anything to keep this linkage captured. I thought I would just bend the open slot closed on the carb lever, but that metal is very hard and would probably break before it bent.

    How can I prevent this rod from coming loose?

    Does anyone have a diagram of this linkage, or a PDF service manual?
     
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  2. jbqwik

    jbqwik ArboristSite Lurker

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    If there's any plastic in the linkage chain then the opportunity for wear is always present. I can't visualize this setup but here's one cheap band-aid: Cinch a small plastic tie wrap (a.k.a. cable ties, come in sizes from tiny to huge, at any auto parts /Radio Shack /etc.) around the two parts. If no binding, then maybe a reasonable fix?
     
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  3. Dan_IN_MN

    Dan_IN_MN Addicted to ArboristSite

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  4. Fish

    Fish Account Hold

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    Sounds like someone has bent the throttle rod already....
     
  5. bennn*e

    bennn*e AboristSite Guru

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    there was a revision done on these probably 2-3 years ago, they re designed it to hook the other way and we haven't had a problem since. ill have a look tomorrow if there was a change in part number or just a running change over
     
  6. Fish

    Fish Account Hold

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    Never heard of any revision, been parting them out for 5 years now, working on them a lot longer

    View attachment 231725
    [​IMG]

    The return spring on the throttle rod on the carb and the spring on the trigger keep the rod tight

    View attachment 231726

    [​IMG]
    To remove the throttle rod, squeeze the trigger, and hold the throttle on the carb open.
     
    Last edited: Apr 1, 2012
  7. Fish

    Fish Account Hold

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    While holding the throttle open with a screwdriver, release the trigger.

    View attachment 231728

    [​IMG]

    And move the throttle rod to the right
     
  8. Fish

    Fish Account Hold

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  9. Fish

    Fish Account Hold

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    The only changes/revisions I have noticed are in the plastic ring expander in the intake boot, and the real recent change to the better quality green fuel line.

    View attachment 231730


    [​IMG]
     
  10. godfreydanials

    godfreydanials New Member

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    Tell me more...

    Fish,

    I do have a return spring on the carb throttle shaft, but the linkage is just flopping around. Do you have a picture, or can you describe what I am looking for on the trigger end of the linkage for a spring? I will go out to the barn in the morning and have a look. I took down a big willow today with the Husky and don't have enough left in me to go back out tonight. I would like to use the 170 to cut the small stuff up.

    Thanks for your help, I really appreciate it.
     
  11. Fish

    Fish Account Hold

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    The spring on the trigger end is in the black plastic handle part, you need a new throttle rod if both springs are working....

    Folks like to bend chit before thinking...........................................
     
  12. bennn*e

    bennn*e AboristSite Guru

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  13. Fish

    Fish Account Hold

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    Wow, been parting them out for 5 years, never noticed the difference, kind of a subtle change, but the change makes sense.
     
  14. godfreydanials

    godfreydanials New Member

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    Thanks guys for the jpegs. I took the throttle rod out and sighted down the end of it. The flat link that goes through the trigger was about 15* off of perpendicular to the vertical end below the hook at the throttle plate. I grabed both ends with pliers and twisted the rod clockwise until they appeared to be square. I ran the saw for a couple of hours yesterday with no problems. If it comes off again, I will find a new style throttle rod to replace this one.
     

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