Stihl - Starting Problems

Discussion in 'Mechanic and Repair' started by finneylawns, Jun 11, 2011.

  1. finneylawns

    finneylawns LawnSite Member
    Messages: 59

    I have a FC 90 stick edger (6 months old) and FS 90r trimmer (10 months), and both of them are having similar starting issues.

    The first start of the day both will start on the first or second pull (usually on the first), no pumping of the bulb and setting the throttle to the "Start" position, choke left open. They both fire off and reach "Starting" running power in about 2 seconds or less.

    After that, it goes down hill. (if the machine is allowed to sit longer than 5 minutes or so, the amount of time between lawns)

    I have tried a number of starting combinations, but the best combination I have found is to pump the bulb a 2 to 3 times, set the throttle to wide open, choke left open, and pull anywhere from 10 to 20 times. When it finally starts, it will start real slow and gradually increase to full speed taking about 10 to 15 seconds to reach full speed. While it is increasing in power, it smells like it is "flooded". I have tried to not pump the bulb to try and alleviate this "flooded" condition, but the machine is even harder to start.

    Once they are running I have no issues with power, dying, or idling. They run great.

    Things that I have done:

    * Always used properly mixed fuel with 93 octane, and used the orange bottle of Stihl 2-cycle oil, but recently switched to the Gray bottle. (single guy operation)
    * Have changed the Spark plug
    * Have cleaned the machines with Seafoam and have run numerous tanks with Seafoam
    * Adjusted the Idle up to just before the head or blade will start to turn on its own.

    Things that I have not tried:

    * Adjusting the High or Low needles
    * Changing the air filter (Have blowed them out with an air compressor)

  2. jkason

    jkason LawnSite Senior Member
    Messages: 546

    Take the carb off and remove the side of the carb away from the primer. There's an internal filter screen that regularly gets clogged with very fine dirt/dust.
    Clean that out and you should be back to normal.

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