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Stihl 026: Idle Speed Too High

Discussion in 'Chainsaw' started by juniormarbles, Sep 9, 2018.

  1. juniormarbles

    juniormarbles ArboristSite Lurker

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    My Stihl 026 chain runs on in idle (clutch off), despite perfect L and H mixture set-up, and, most crucial, despite the LA idle speed screw all the way counter clockwise (lowest idle speed setting). What else can I do to lower the idle speed? Nothing has changed on the saw for years; though this had been gradually getting worse, I do not remember ever being able to lower the idle speed so much that it would kill the engine. I.e. it always ran fast in the lowest setting.

    Any ideas?

    Thanks in advance,
    JM
     
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  2. Big_Wood

    Big_Wood westcoast dweller

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    When you say perfect H/L I assume you mean they are set to what the covers says to set them too? Those are baseline numbers that require fine tuning but it should run good there. If it doesn’t You can add fuel by turning out the L screw while running which should bring idle down. This is only a cover up for the issue needing fixed and shouldn’t be run this way. It’s almost always the flywheel side seal on an 026.
     
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  3. HarleyT

    HarleyT Tree Freak

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    Take off the air filter and take a pic of the carb/throat, and put it up.
     
  4. kenton.a.frank

    kenton.a.frank ArboristSite Operative

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    Too high as in audibly too high or chain moves?


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  5. juniormarbles

    juniormarbles ArboristSite Lurker

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    Too high in terms of chain moving. See my first sentence.
    I know how to set up idle mixture on chainsaws, roto-tillers, mopeds, go-carts and the like. On my 026 it's set perfectly at the smooth idling hump between starvation stumbling and too rich coughing. Lowering the idle speed by running it richer than necessary defeats the purpose, hurts my lungs and the environment, and, as you say, would only cover up the issue.
    But your "flywheel side seal" is an intriguing idea. Can you say more? Are we talking about some kind of air leak?
    Will do this afternoon.

    Thank you all.
     
  6. HarleyT

    HarleyT Tree Freak

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    Yeah, these guys say "seals" almost every time with no real info....
     
  7. juniormarbles

    juniormarbles ArboristSite Lurker

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    DSCF1571.JPG throttle flap is completely closed, if that is not clear enough from the picture. Dirt is from removing air filter.
     
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  8. kenton.a.frank

    kenton.a.frank ArboristSite Operative

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    Hey if you are too good to clarify then I guess I wouldn’t ask. If it is idling smooth and sounds right the I’d check the clutch springs. If it has progressively gotten worse they could be getting weak causing the clutch to engage at a low RPM. I would weed out the air leak on primary inspection if you are able to get a good tune on the carb without it being excessively out of the 1/1 realm on H and L. But what do I know I had to ask a clarifying question when trying to help someone diagnose their saw over a forum.


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  9. Mad Professor

    Mad Professor Addicted to ArboristSite

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    If mixture is O.K. , as mentioned, check the clutch. Bearing being bad can do that.

    I bought a filthy 026 off CL and the clutch was stuck because of the amount of debris inside the cover. The friction started to melt the clutch cover.

    Clean it up, and check the springs and bearing..

    The flywheel side seal is a weak spot on the 026 if clutch is O.K.

    That CL DSC_0027.JPG DSC_0033.JPG 026 was $95 and it cleaned up nice
     
  10. Big_Wood

    Big_Wood westcoast dweller

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    Without any info? I get what you saying about some but that ain’t me. He says he’s got his damn idle screw backed out with his L set correctly and it’s still idling high. If the springs were the problem he would have no problem killing the thing with turning his idle down. It’s also not possible to tune the low speed with a clutch catching and he says his low is perfect. Not to mention it’s in an 026. I’ve replaced more 026/036 flywheel side seals then any other saw I can think of. Doesn’t mean it is the seal but it’s likely an air leak in this particular case. The reason I mentioned giving it more L was because if the carb can kill the idle down with fuel it’s likely not a fuel delivery issue.
     
  11. drf255

    drf255 BAD CAD

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    Agreed. As pointed out above, the Fly side seal is usually the culprit.

    Put a tach on the saw. If the saw is below factory setting and the chain still moves, you need springs.

    But, if I’m reading correctly, you say no matter how much you back off the LA screw, the idle won’t come down. And also that it keeps getting worse.

    Sound like a classic air leak. You need to vac and pressure test the saw at this point, or you are wasting time and money.

    My bet is the Fly side seal, but it really can be anything.
     
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  12. farmer steve

    farmer steve outstanding in my field, 5150

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    i had problems with getting a good tune on my 26 and finally found that the intake boot clamp was loose and sucking air. i had several guys look at it at a GTG and everyone missed it. :omg:
     
  13. Mad Professor

    Mad Professor Addicted to ArboristSite

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    You're right. Maybe vac/pres test is in order if idle screw is backed out and still racing.
     
  14. juniormarbles

    juniormarbles ArboristSite Lurker

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    Maybe my understanding of this saw is flawed, but how do the clutch springs come into play when the clutch is disengaged (lever pulled back)? The clutch works fine and instantly stops the chain movement cold when the lever is pushed forward (clutch engaged).

    If it's a vacuum leak, how do I diagnose the source without specialty tools?
     
  15. kenton.a.frank

    kenton.a.frank ArboristSite Operative

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    I think I understand your post correctly, I believe you have your parts confused. The “lever pulled back” is the chain brake being disengaged. The lever is controlling the band that wraps around the clutch drum. When it is engage a spring hold pressure to tighten the band around the drum not allowing it to move. When it is pulled back it snaps into place with the brake spring pulled. The clutch springs that are being referred to are under the clutch drum attached to the clutch shoes. My simple test is if you take the clutch off and you can easily bend/flex the shoes up and down they are getting weak or if they just fall down they are weak. Sometimes you will even find one spring is broken. Which when they are weak or broken they allow the clutch to expand under a slow speed thus moving the chain at 2800 rpm when it shouldn’t with fresh springs.


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  16. juniormarbles

    juniormarbles ArboristSite Lurker

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    Very helpful. Thank you. I will follow up.
     
  17. juniormarbles

    juniormarbles ArboristSite Lurker

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    ..but on second and third read, I am still confused:
    Regardless of any chain movement or clutch on or off, the engine runs way too high. And, though the speed comes down and the clutch, once activated, instantly stops the chain, the engine clearly struggles against the clutch and as soon as I release it, speeds up. If it was an air leak, how would I be able to adjust the mixture screws within the usual range? Woud it not require settings way out of the ordinary?
     
  18. HarleyT

    HarleyT Tree Freak

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    Thanks for putting up the pic with the air filter off.
    I was wanting to get a look at the throttle flap, to rule out a linkage/throttle flap problem.
     
  19. HarleyT

    HarleyT Tree Freak

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    I would start by removing and going through the carb, and do an inspection of all of the intake/rubber parts. It is likely due for a carb rebuild anyway, as it is a wear/maintenence thing to do, and the issue may be right there.
    If you are capable of doing a leakdown test, it is a fairly procedure on that model.
    Take off the muffler and peek at your piston before buying any parts.
     
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  20. Chainsaw Jim

    Chainsaw Jim CJ Saws, LLC

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    Back the low screw out until the idle drops and the chain stops moving. Then while running, hold it at wide open throttle for a good 5 seconds to see if the max rpm's hold or keep climbing.
     

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