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  1. #1
    Super Member California's Avatar
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    Jan 2004
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    5,545
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    Sonoma County
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    Yanmar YM240, YM186D, and another YM186D

    Default Lawnmower seized up. Fixable?

    I went out to start the lawnmower for the first time this season and it's too stiff to turn. I can turn the blade by hand, against considerable resistance. It sounds like the rings are gouging the bore badly.

    This is a 5 hp Briggs IC. The oil looks clean. It ran fine last year.

    The only thing that occurs to me is to turn it sparkplug-down to let the crankcase oil drain into the cylinder, to oil the rings.

    I assume these are throwaway engines if the bore is shot.

    Any advice?

  2. #2
    Veteran Member K7LN's Avatar
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    Feb 2009
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    Michigan
    Tractor
    JD455 & JD790

    Default Re: Lawnmower seized up. Fixable?

    At 5hp, I assume that you're talking about a push mower. For the last several years, they have had a brake on them that is controlled by some type of hand grip on the handle. It sounds more like the brake is hanging up on you. Pull the top cover off and have a look.
    JD 790 w/70 FEL & 7 BH on turf tires
    JD 455 w/60" MMM & 54" front blade

  3. #3
    Silver Member
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    Jan 2009
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    124
    Location
    Loudon, New Hampshire
    Tractor
    Agco ST35

    Default Re: Lawnmower seized up. Fixable?

    Remove the spark plug and spray some penetrating oil in the cylinder. Let it sit for a half-hour and try again to turn the engine over using the blade. Repeat as needed. If it was running when you put it away it should run again.

    I don't think you'd be able to hear the rings rubbing on the cylinder wall.

    Does your mower use a mechanical brake to stop the blade when the safety brake handle is released? Is the brake releasing when the handle is released?

    Other things: Is the mower self-propelled? Any chance the drive belt is broken/jammed in the pulley?

    Were you turning the motor over with blade and the spark plug installed? (BTW: this isn't a good idea, if the engine were to start there would be **** to pay) If so, make sure the cylinder isn't full of gasoline.

  4. #4
    Super Member California's Avatar
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    Jan 2004
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    5,545
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    Sonoma County
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    Yanmar YM240, YM186D, and another YM186D

    Default Re: Lawnmower seized up. Fixable?

    A blade brake never occurred to me. I had never heard of one on these engines.

    Yes, the sound is consistent with that. It's not self propelled so that brake is the likely culprit.

    If this rain ever lets up I'll go check that.

    Is the brake up on the flywheel, or inside it? Or in the blade engage/disengage stuff below? Last time I took apart a B&S was 25 years ago. I'm not familiar with this new fancy stuff.

    Thanks!!!

  5. #5
    Silver Member
    Join Date
    Jan 2009
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    124
    Location
    Loudon, New Hampshire
    Tractor
    Agco ST35

    Default Re: Lawnmower seized up. Fixable?

    The brake should be inside the deck, connected to the vertical crankshaft of the motor. They will be a cable that runs from the brake to the operator brake handle, and that cable is a common problem. When you squeeze the handle, is the pressure normal? When you move the handle can you see the end of the cable that connects to the brake moving?

    BTW: The blade brake is required to stop the blade when the handle is released. It also kills the ignition. On these type of mowers the blade is the flywheel.

    Some of the higher-end mowers use a blade brake clutch to allow the motor to run without spinning the blade.

  6. #6
    Super Member California's Avatar
    Join Date
    Jan 2004
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    5,545
    Location
    Sonoma County
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    Yanmar YM240, YM186D, and another YM186D

    Default Re: Lawnmower seized up. Fixable?

    I suspect the cable is the problem, not releasing the brake.

    I'll go troubleshoot it when the weather clears.

    Thanks!!!

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