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31hp Kawasaki Backfire

Discussion in 'Mechanic and Repair' started by lawnspecialties, Jun 2, 2009.

  1. lawnspecialties

    lawnspecialties LawnSite Silver Member
    Messages: 2,524

    What causes my 31hp Kawasaki to backfire every time I cut the throttle back quickly? I can cut it back very slow and no problem.

    This started at the start of the season and I just thought it was due to old gas. I don't winterize since my mowers do get run once or twice a month during the winter months. That old fuel is long gone but it still does it.
  2. newtostone

    newtostone LawnSite Senior Member
    from NY
    Messages: 681

    I have no idea why but my 34 hp kawi does the same so I would love to hear why this happens. Mine only has 50 hours on it.
  3. RonAyersMotorsports

    RonAyersMotorsports LawnSite Senior Member
    Messages: 854

    Because you shouldn't shut engines off at low speed or quickly idle it back. Most engines will back fire when doing so. Half speed shut offs prevent this!
  4. lawnspecialties

    lawnspecialties LawnSite Silver Member
    Messages: 2,524

    This engine never did it last year. My 27hp Kawasaki never does it nor my 21hp Kawasaki. My former Kawasakis never did it as well. It's just been my 31hp Kawasaki and it only started at around 170 hours.

    The only time I've ever had backfire issues before is with Kohlers.
  5. mowerknower

    mowerknower LawnSite Senior Member
    Messages: 766

    Tried premium fuel. It doesnt ignite as easy so if you have a hot spot in your cylinder it wont backfire.

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