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Honda BF45 Air/Fuel Mixture screw?

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  • Honda BF45 Air/Fuel Mixture screw?

    On my carbs I have a copper/brass adjustment screw on the top and a darker black screw on the bottom.

    Which one is the Air/Fuel mixture?

    I also noticed one of the copper/brass mixture screws is not lined up the same as the other 2 - it's about 2 hours off. (Looking at it like a clock) - Should I also adjust this so that all 3 are set the same?

    Thanks!


  • #2
    Re: Honda BF45 Air/Fuel Mixture screw?

    The brass flathead screw is the idle mixture .The black screw is simply a float bowl drain.These carbs can require a little tweaking so if they are not identically set and things are running properly all is well.What problem are you trying to solve?

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    • #3
      Re: Honda BF45 Air/Fuel Mixture screw?

      Originally posted by hondon View Post
      The brass flathead screw is the idle mixture .The black screw is simply a float bowl drain.These carbs can require a little tweaking so if they are not identically set and things are running properly all is well.What problem are you trying to solve?
      Thanks, well the idle is okay but the motor has a slight jump left to right while idling.

      Secondly, when I quickly throttle upto half or so the motor falls on its face for a second before it revs. Like it may need to be richened up some, a little fuel starved.

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      • #4
        Re: Honda BF45 Air/Fuel Mixture screw?

        You may well need to richen up a little but keep in mind that you have an accelerator pump in that throttle mechanism that incorporates a dashpot and a checkvalve.Hondas carb engines have never really loved to be stood on but if this is something new to you ,I'dd start with that check valve.

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        • #5
          Re: Honda BF45 Air/Fuel Mixture screw?

          Originally posted by hondon View Post
          You may well need to richen up a little but keep in mind that you have an accelerator pump in that throttle mechanism that incorporates a dashpot and a checkvalve.Hondas carb engines have never really loved to be stood on but if this is something new to you ,I'dd start with that check valve.
          Thanks, I did quarter turns all the way back out for about one revolution. It did seem a bit better but I had the feeling the carbs are either WAY off or that wasn't really the issue.

          Any idea how many turns out from all the way in these should be? How can I tweak each carb individually? Just unplug sparkplug wires to single out each carb and run one at a time?

          Thank you for the note on Accelerator pump, How can I go about checking this? Any manual way? Just Visual inspection?

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          • #6
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            Re: Honda BF45 Air/Fuel Mixture screw?

            That check valve is a little grey valve between the dashpot and the carbs with an arrow on it. The arrow should be pointed at the carbs and is only a one way valve that allows air into the floatbowl to displace fuel on acceleration.Use a small syringe and with a little rubbing alchohal[ca'nt believe I misspelled that]and gently squeeze a little into each end.You should only get flow in the direction of the arrow.Tweaking is another story. You will first need to know if the valves are adjusted properly,compressoin is where it should be and the carbs are in sync.It can be quite a little dance.

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