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  • #16
    All I know for sure is that when my idle jets were not working correctly, once I hit about 2500-3000 the bike kicks you in the back end like an ex-wife!! That is the mains kicking in, and it seems that the needle rising is what lets the fuel flow more through the mains. Twist that grip all you want and it never kicks like it does at those RPMs, even when I hammer it in first from 1000 RPM up. Just my personal experiences.
    Life is what happens while your planning everything else!

    When your work speaks for itself, don't interrupt.

    81 XS1100 Special - Humpty Dumpty
    80 XS1100 Special - Project Resurrection


    Previously owned
    93 GSX600F
    80 XS1100 Special - Ruby
    81 XS1100 Special
    81 CB750 C
    80 CB750 C
    78 XS750

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    • #17
      One more tidbit about idle mix screws. You can tell the function by just looking at the carb. If the screw is located on the air inlet side, the screw controls the air in the mix. If the screw is located on the engine side, it controls the fuel in the mix. The two types work opposite of each other, ie if it's an air mix screw, turning in richens, if it's a fuel mix screw, turning in leans.
      Former owner, but I have NO PARTS LEFT!

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      • #18
        Just to add to it a little:

        The air is added to the fuel by the holes in the pilot jet.

        The number of air holes in the pilot jet and the size of the fuel metering hole determine the air/fuel ratio.

        The mixture screws control the amount of pre-mixed air/fuel delivered at idle and off-idle.

        The transition ports feed more of the air/fuel mix as the throttle is opened further until the slides and jet needles lift and begin to clear the needle jets/emulsion tubes, then the mains take over and the bike tries to blast out from underneath you.
        -- Scott
        _____

        2004 ST1300A: No name... yet
        1982 XJ1100J: "Baby" SS Brakes, '850 FD, ACCT
        1980 XS1100G: "Columbo" SS Brakes, '850 FD, ACCT
        1979 XS1100SF: "Bush" W.I.P.
        1979 XS1100F: parts
        2018 Heritage Softail Classic 117 FLHCS SE: "Nanuk" It's DEAD, it's not just resting. It is an EX cycle.

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        • #19
          Originally posted by 3Phase View Post
          Just to add to it a little:

          The air is added to the fuel by the holes in the pilot jet.

          The number of air holes in the pilot jet and the size of the fuel metering hole determine the air/fuel ratio.
          hi scott,
          the air jet at the back of the carb bell adds air to the idle circuit, the holes
          in the pilot jets helps to atomise the fuel being delivered.
          pete


          new owner of
          08 gen2 hayabusa


          former owner
          1981 xs1100 RH (aus) (5N5)
          zrx carbs
          18mm float height
          145 main jets
          38 pilots
          slide needle shimmed .5mm washer
          fitted with v/stax and uni pod filters

          [url]http://www.youtube.com/watch?v=3pA8dwxmAVA&feature=mfu_in_order&list=UL[/url]

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          • #20
            Originally posted by petejw View Post
            hi scott,
            the air jet at the back of the carb bell adds air to the idle circuit, the holes
            in the pilot jets helps to atomise the fuel being delivered.
            Yep, I thought of the pilot air jet after the editing time expired and I saw you'd already called me on it and elucidated. Thanks!

            The number and size of the air bleed holes and size and location of the fuel metering hole in the pilot fuel jet determines how much of the available air from the pilot air jet is mixed with the fuel in the pilot fuel jet.

            Better, too sparse or too windy? <hopeful look>
            -- Scott
            _____

            2004 ST1300A: No name... yet
            1982 XJ1100J: "Baby" SS Brakes, '850 FD, ACCT
            1980 XS1100G: "Columbo" SS Brakes, '850 FD, ACCT
            1979 XS1100SF: "Bush" W.I.P.
            1979 XS1100F: parts
            2018 Heritage Softail Classic 117 FLHCS SE: "Nanuk" It's DEAD, it's not just resting. It is an EX cycle.

            Comment

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