Stihl trimmer runs without squeezing trigger

Discussion in 'Mechanic and Repair' started by tinman, May 10, 2005.

  1. tinman

    tinman LawnSite Bronze Member
    from ga
    Posts: 1,348

    Any way to easily fix this.... Tried the "idle screw on back of trimmer" to no avail. Does not run wide open, but about 70% . Makes it hard to delicately trim arounf plants, fences, etc.

    Trimmer is a Stihl FS 80 I beleive. Thanks
     
  2. mike76

    mike76 LawnSite Member
    Posts: 27

    You need to check the muffler screen to see if its stopped up. Check to fuel lines to see if they have a split or are dry rotted. Try this and see if this works for you, good luck..
     
  3. tinman

    tinman LawnSite Bronze Member
    from ga
    Posts: 1,348

    No,,,I'm sorry.... It runs fine... the problem is the head spins too fast without squeezing the trigger. Like the throttle is stuck.
     
  4. dvmcmrhp52

    dvmcmrhp52 LawnSite Platinum Member
    from Pa.
    Posts: 4,205



    When's the last time the air filter was replaced?
    Sounds like the engine needs air or the low idle screw is way out of wack............
     
  5. mike76

    mike76 LawnSite Member
    Posts: 27

    Sorry i misunderstud, Undo the throttle cable and see if the trimmer idles and if it does them you need to check the cable.
     
  6. dvmcmrhp52

    dvmcmrhp52 LawnSite Platinum Member
    from Pa.
    Posts: 4,205




    Could be the handle on the shaft that the cable goes to has moved and stretched the cable too tight...............
     
  7. tinman

    tinman LawnSite Bronze Member
    from ga
    Posts: 1,348

    Will try that...Thanks

    Replaced air filter last year
     
  8. mdmowerman

    mdmowerman LawnSite Member
    from 20833
    Posts: 77

    clutch gone bad? same thing here,about 150 to fix, might be worth a new one, your call.
     
  9. Gautreaux's LNG

    Gautreaux's LNG LawnSite Senior Member
    Posts: 379

    Check the throttle cable for not being in the correct place. for some reason the cable is pulled to keep the throttle open position. It may have moved out of the holder for the metal end causing this condition. disconnect the cable from the carb. If the trimmer still runs higher than normal its in the carb. If it runs ok and you can manually control the speed with your hand the cable is caught or out of the correct place. Good Luck
     
  10. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,075

    The problem is likely in the throttle cable adjustment not the idle adjustment on the carb. If there gets too much slack the little bullet on the end of the cable can get out its hole in a carb actuating arm and the unit wil run fast. Get it back in and adjust the cable screw for no play when the throttle lever is not operated, so the bullet can't get out!
     

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