Stihl FS 80R bogging at WOT

Discussion in 'Mechanic and Repair' started by jtkplc, Mar 17, 2007.

  1. jtkplc

    jtkplc LawnSite Silver Member
    Posts: 2,646

    At the end of last season I was having problems with my Stihl FS 80R bogging down on and off when I would run it wide open. It wouldn't do it all the time, it seemed to come and go. Sometimes when it would bog down, if I brought it back to idle and then reved it up again it would come out of it for a little while. I don't know what else to check. My dad is a mechanic, but not for small engines. We've checked everything he knows about including the fuel/air mix ratios, I put a new spark plug in, and checked fuel lines. Does anyone know what else to check or what could be wrong? I want to try to fix it myself if I can to save the money from taking it in to my dealer. Thanks, jtkplc.
  2. RLW

    RLW LawnSite Member
    Posts: 46

    Did you pull out the spark arrestor from the muffler ? They come out like a spark plug. Thing will gum up from 2- stroke oil & choke out the engine with back pressure. If you can't see through the mesh, burn it off with a torch & hit it with a wire brush.
  3. DandG

    DandG LawnSite Member
    Posts: 37

    yea i second his opinion about the spark arrestor i have fixed many a stihl trimmer that way
  4. Tadams

    Tadams LawnSite Senior Member
    Posts: 788

    Clean the spark arrestor and if that doesn't fix it you will have to rebuild the carb. I just got finished with mine. It is not very hard to do- you can get a rebuild kit at your dealer or through one of the online suppliers. You will have to take the carb off and get the numbers off of it to get the right kit. If you decide to do this yourself- send me a pm and I can walk you through it.
  5. TurfConcepts Inc

    TurfConcepts Inc LawnSite Member
    Posts: 52

    My old FS80 does the same thing. I pulled the arrestor and changed the spark plug and it ran fine for a day. Now it is back to it's old ways. Tadams, can you post the step by step for the carb rebuild?
  6. jtkplc

    jtkplc LawnSite Silver Member
    Posts: 2,646

    I will have to double check, but I'm pretty sure I checked the arrestor and it wasn't even there. I think it must have fallen out somehow because there was no screen where there should be. I guess a rebuild is in my future. How much do they cost? Thanks for your help.
  7. Budget

    Budget LawnSite Senior Member
    from Pa.
    Posts: 368

    At wot sounds like its a lean bog, make sure carb is adjusted right.
  8. jtkplc

    jtkplc LawnSite Silver Member
    Posts: 2,646

    What exactly does that require doing?
  9. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    Make sure the fuel tank is venting. When it acts up loosen the fuel cap and see if this takes care of the issue? Just another thing to check....
  10. EMTDUCK1984

    EMTDUCK1984 LawnSite Member
    Posts: 180

    Sounds Like You Have Some Water Or Trash In The Carb When You Accelerate It Causes The Trash To Get Over Near The Needle And Closes The Needle Off Slightly So It Acts Like It Boggs Down

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