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Honda push mower blows black smoke when throttling up?

I have a Honda push mower with a GCV160 engine on it. When ever I throttle up fast or from idle it will blow black smoke from the exhaust for a few seconds. It's not burning oil as I know what that smells like and this smells like its running rich. I have put a new air filter in, rebuilt the carburetor, (it's spotless inside), and tried to make adjustments to the mixture. The only adjustment screw turns 1/4, non of which make a difference. The float needle isn't leaking as I checked and tested it, and the choke isn't sticking. Also replaced spark plug and test spark and all seem to be good, it's getting a white-ish spark.

Does anyone have any ideas? I'm at a loss, it runs really well but it's a lot of black smoke when the rpm changes.

6 Answers

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  • Anonymous
    2 months ago

    Black means you never go back.   I would have the wheel alignment checked.  Chances are the catalytic converter is changing the gas into coal.

    Maybe try Home & Garden instead of AUTOMOTIVE.?

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  • 2 months ago

    Too rich mixture is what causes that issue. Still might see it on a car but once we moved to fuel injected engines, it's hard to recreate this phenomenon. Have you tried it with and without the air filter in place? An air filter can sometimes get too much oil on it (or water) and barely enough air will get through for the engine to run and it will therefore run rich. Water usually stalls any engine if the air filter gets wet. It can't suck air through a wet filter.

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  • Anonymous
    2 months ago

    Worry about the problem when the black smoke is constant.

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  • Anonymous
    2 months ago

    WRONG FORUM. Go to the M&R forum in the Home & Garden category. 

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  • Anonymous
    2 months ago

    Then, don't "throttle up fast".

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  • Anonymous
    2 months ago

    It's likely just a rich mixture from the autochoke which I think Honda has, I wouldn't worry about it if it's short lasted.

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