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Stihl trimmer running poorly

Discussion in 'Mechanic and Repair' started by greenfrog, Oct 16, 2012.

  1. greenfrog

    greenfrog LawnSite Member
    Messages: 10

    I have a Stihl FS 100 RX trimmer and it shakes and sputters like it's running out of gas. The trimmer head continues to spin even without hitting the throttle. I replaced the carb and cleaned the exhust screen and it still is running poorly. Any suggestions would be much appreciated. Thanks!
  2. MR-G

    MR-G LawnSite Senior Member
    Messages: 479

    4 mix engines require that the valves be cleaned/decarbonized every so often....also check to see that no wires are bare and grounding out...check to see wires at coil are tight fitting....most likely the valves though...if they cant seat properly you in effect change the timing and cause the engine to skip a beat or a cycle....this could be causing higher idle and erratic performance. if none of this fixes it you could have a broken flywheel keyway causing the flywheel to slip on its shaft .(easy fix)
  3. Darryl G

    Darryl G LawnSite Fanatic
    Messages: 8,613

    They all run that way, get used to it :p

    One thing that is often neglected in the fuel filter. I would replace that as well as all of the fuel lines.

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