V twin backfire

Discussion in 'Lawn Mowing' started by specialtylc, Feb 22, 2004.

  1. specialtylc

    specialtylc LawnSite Bronze Member
    Messages: 1,656

    What causes these v twin gas engines to back fire when you shut them off. My kohler 25 has been doing it for years. Last summer I ran other makes that were brand new and they did the same thing.Honda,Kawasaki , Kohler all did it.
  2. metro-hp_48

    metro-hp_48 LawnSite Senior Member
    from TN
    Messages: 874

    Several diff. threads on the backfiring subject. Most just let the mower idle for a min. or two, and that will take care of it. Some have had to turn the fuel off, and let it run out. As far as I know, the single cylinders will backfire, too. Got a 12.5 KAW that will deff. do it.
    What causes it? unburnt fuel, hot motor, ect.
  3. mckell68

    mckell68 LawnSite Member
    Messages: 46

    No backfire from my B/S 18 hp Vanguard twin---a good motor!!!
  4. metro-hp_48

    metro-hp_48 LawnSite Senior Member
    from TN
    Messages: 874

    The Vanguard motors are very good. But all motors can do it, doesn't make them any better or worse than any other. My FH500V has never backfired.
  5. Ryan Lightning

    Ryan Lightning LawnSite Senior Member
    from CA
    Messages: 554

    Try turning it off at quarter are half throttle.
  6. 65hoss

    65hoss LawnSite Fanatic
    Messages: 6,360

    New kawi motors do it bad until they break in. After they get some hours on them they aren't as bad. My w/b kawis I let them idle for about 1-2 minutes in the cooler weather and 2-4 minutes in the heat before shut down.
  7. Pecker

    Pecker LawnSite Bronze Member
    Messages: 1,454

    My Kawi 25 V-twin did it alot until it had about 50 hours on it. It did it more when killing the engine from idle. Try shutting it off at about 1/4 to 1/3 throttle and it won't do it anymore. At least mine didn't.
    A quote from my owner's manual (JD 757):

    "IMPORTANT: Avoid damage! To help prevent engine backfiring, throttle lever should be set at the 1/2 position prior to stopping the engine."
  8. turf9

    turf9 LawnSite Member
    Messages: 233

    I have the 20 hp carb type Kohler says in the manual (Walker) not to turn off the ignition at idle. Move the throttle up a little then turn er off.It goes on about a anti backfire solinoid, In any event it does not backfire when I follow this procedure. But once in a while it's good to stir up the neighborhood after cutting keeps everyone in line lol.
  9. specialtylc

    specialtylc LawnSite Bronze Member
    Messages: 1,656

    THANKS for info on not shutting off at idle. Will try that in spring and see if it helps.

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