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  1. #1

    Join Date
    May 2011
    Posts
    3
    Location
    Missouri
    Mower
    Murray

    Question Mower stuttering and black smoke.

    Hi, we've a mower giving us problems and wondering if we could get some advice.
    It's an 8 year old 22" Murray push mower with a 4 HP Briggs & Straton engine. I admit, we haven't maintenanced it as well as we should. Although, I always check the oil (SAE 30) and never leave old gas in it.

    It ran perfectly fine until last week without warning it started sputtering and losing power, going rrrr-RRRR-rrrr-rrrr-rrrr-RRRR... and sputtering black smoke.
    It has no problem starting, it starts right up.
    Also, like 30 seconds before it runs out of gas it'll suddenly start working fine and the engine runs nice and normally.

    We replaced the air filter (the spongy kind... I know you're supposed to be able to wash them out, but it was pretty bad. Thought it best just to replace it.)
    Any ideas of what I can do?
    Thanks!

  2.  

  3. #2

    1,000 Post Club

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    May 2010
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    2,305
    Location
    Illinois
    Mower
    kioti/rhino finish mower

    Re: Mower stuttering and black smoke.

    if that is the engine with the carb mounted on top of the fuel tank, you need a new diaphragm between the carb and the tank. the carbs tend to warp on the engine side of the carb and the diaphragm pulls out and then sucks fuel around the edge and makes it run rich.
    ILLINOIS ENGINE, BEECHER CITY, IL
    BRIGGS AND STRATTON MST (MASTER SERVICE TECHNICIAN)
    Sales and Service for Dolmar, Poulan, Briggs and Stratton, Kohler, Lauson(Tecumseh, LCT), Generac, Brute.
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  4. #3

    Join Date
    May 2011
    Posts
    3
    Location
    Missouri
    Mower
    Murray

    Re: Mower stuttering and black smoke.

    Thanks for the reply!
    Unfortunately, I'm not engine part knowledgeable. All I can tell you is the fuel tank sits immediately below the primer button which is immediately below the air filter. And then the exhaust is on the opposite side of the motor.
    If what you say is the likely cause, is that something that's easily self-serviced? I'm not engine knowledgeable or experienced, but I follow instructions real well. :)
    I'm just afraid taking the mower to a qualified service person will cost more than the mower itself did.
    Thanks for the feedback!

  5. #4

    Join Date
    May 2010
    Posts
    5,437
    Location
    Kansas, Butler county, Just east of DooDah
    Mower
    CTL

    Re: Mower stuttering and black smoke.

    Quote Originally Posted by Mechphisto View Post
    but I follow instructions real well. :)
    Welcome to the LMF...
    Well here is a young fellow doing exactly what you need to do, easy to DIY...
    He has not the most sanitary working conditions ... but hey, he gets it done...
    this guy is doing it mostly with one hand (he is holding the camera) while doing it...
    Watch this and you will see its not a big job... YouTube - How To Replace The Diaphragm On Briggs And Stratton Primer Plastic Carburators On Metal Gas Tanks
    KennyV

  6. #5

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    Two-Stroke's Avatar
    Join Date
    May 2010
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    1,434
    Location
    Atlanta, GA/Cleburne County, AL
    Mower
    Lawn Boy, Toro, Jacobsen

    Re: Mower stuttering and black smoke.

    Quote Originally Posted by KennyV View Post
    Welcome to the LMF...
    Well here is a young fellow doing exactly what you need to do, easy to DIY...
    He has not the most sanitary working conditions ... but hey, he gets it done...
    this guy is doing it mostly with one hand (he is holding the camera) while doing it...
    Watch this and you will see its not a big job... YouTube - How To Replace The Diaphragm On Briggs And Stratton Primer Plastic Carburators On Metal Gas Tanks
    KennyV
    That's an impressive video -- not that the job is all that hard but shooting the video with his left and doing the repair with his right.
    General "Buck" Turgidson: Sir, you can't let him in here. He'll see everything. He'll see the big board!

    -- from the movie: Dr. Strangelove... (1964) -- now available on Netflix streaming -- one of the funniest movies ever

  7. #6

    Join Date
    May 2011
    Posts
    3
    Location
    Missouri
    Mower
    Murray

    Re: Mower stuttering and black smoke.

    Quote Originally Posted by KennyV View Post
    Welcome to the LMF...
    Well here is a young fellow doing exactly what you need to do, easy to DIY...
    ... KennyV
    Thanks!
    And thanks for the link! That looks just like my mower. And it looks like I can totally handle the job. :) I think the hardest part is emptying the gas tank without wasting any! (That stuff's liquid gold right now.)
    Now I need to find a place that sells the diaphragms...
    Thanks again! :)

  8. #7

    Join Date
    May 2010
    Posts
    5,437
    Location
    Kansas, Butler county, Just east of DooDah
    Mower
    CTL

    Re: Mower stuttering and black smoke.

    Quote Originally Posted by Two-Stroke View Post
    That's an impressive video -- not that the job is all that hard but shooting the video with his left and doing the repair with his right.
    Sure is ... one handed repair, shows how easy the job can be...
    Quote Originally Posted by Mechphisto View Post
    ....
    Now I need to find a place that sells the diaphragms...
    Post back with how well it worked ... Looked like he bought his at 'True Value' hardware for just under $5....
    KennyV
    PS... since this will be your first diaphragm repair .. use both hands...

  9. #8

    Join Date
    May 2011
    Posts
    6
    Location
    California
    Mower
    LawnBoy

    Re: Mower stuttering and black smoke.

    My briggs and stratton was doing the same thing. I would be able to start it then start to rev up and down, up and down and then finally just die out.

    Find the air intake valve. It would be behind the air filter. Start the mower and then play with the valve. It could be stuck in the wide open position. Try to close it and see what happens.

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