Stihl KM130 dumping fuel out of carb

Discussion in 'Mechanic and Repair' started by Fubba, Sep 24, 2013.

  1. Fubba

    Fubba LawnSite Senior Member
    Posts: 356

    Fuel dumps out of carb when the motor is shut down. So much so that I have to keep the air filter off, or it will clog the filter and won't start again. What is the problem? I run 100% gas, 93 octane, and Stihl ultra oil. Thanks.
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  2. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,157

    Sounds like the inlet needle is not seating properly allowing it to flood. Could be caused by stiff diaphragm, or dirt, or a worn needle tip. Could also be the main nozzle check valve (if it has one).
    Prolly better for ya to just replace the carb.
     
  3. austins35

    austins35 LawnSite Member
    Posts: 90

    i agree with Fish slap a new carb on it an be done rebuilding (rebuild kit) is a hassle in my opinon not worht the time, money or effort

    use 93 octane gas and treat your gas an you'll be good
     
  4. Blade Runners

    Blade Runners LawnSite Bronze Member
    Posts: 1,021

    Not sure if these carbs have floats but fuel dumping out of a carb is usually a stuck float. I have had it happen n our quads and sometimes you can tap the float bowl with the handle of a screwdriver and it will free it up.

    I also agree with replacing the carb if they aren't to expensive. Sometimes trying to troubleshoot and fix carbs is more trouble than it's worth.
     
  5. Fubba

    Fubba LawnSite Senior Member
    Posts: 356

    So carb then. Nothing to do with the vent on the tank?
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  6. Blade Runners

    Blade Runners LawnSite Bronze Member
    Posts: 1,021

    Yes it would be your carb. Nothing to do with the tank or tank vent would cause a carb to flood. Clogged tank vents actually cause the opposite to happen. They will cause the tank to vapor lock and little or no fuel will flow to the carb.

    Just done some searching and found out these carbs don't have floats. But as Bigfish said, something is keeping your inlet needle or valve from shutting off fuel flow inside the carb.

    The good news is a new carb only sells for about $35-40. At that price I would just get a new one, slap it on and be done with it.
     
  7. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Posts: 728

    A properly working tank vent should only allow air to enter the tank as not to create a vacuum... But should seal off to pressure and not allow any fuel back to the air filter base.

    A tank vent that is stuck closed will not allow air to the tank... However, a tank vent that is stuck open can and will cause fuel to be spit back to the air filter base.

    So, is the fuel coming from the carburetor venturi (A in the picture) OR the tank vent line fitting in the air filter base (B in the picture)?

    Is fuel is coming from A? If so then it would only be a carburetor issue.
    Is fuel is coming from B? If so then a new carburetor would do no good as it is a tank valve that is stuck open (C in the picture).

    Air Filter Base - Tank Vent Line Fitting - Tank Vent.jpg
     
  8. Patriot Services

    Patriot Services LawnSite Fanatic
    Posts: 12,678

    These carbs don't have floats as you would find on a bowl style carb. Its all diaphragms and flexible membranes. The aluminum covers tend to warp when disassembled. The passages are tiny and don't clean well. Kits are rare so you have little choice but to replace the carb. New pipes and filter are a good idea too.
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  9. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,157

    Good photo and explanation! Should be very helpful.

    How'd ya get it so clean ??? lol
     
  10. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Posts: 728

    Thanks! Pictures are always worth a 1000 words.

    I just happened to have a couple hanging around... :laugh:

    P9250001.jpg
     

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