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Why would Cylinder No. 1 run rich?

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    Why would Cylinder No. 1 run rich?

    I have worked out most of the mixture issues but continue to have this weirdness on one cylinder.

    Again, the bike has pods (don't hate) and a 4-1 pipe. The current jetting is:

    Pilot - 17.5
    Fuel Screw - 1.25 turns out
    Air Screw - 2 turns adjusted with ColorTune
    Needle - 4th slot
    Mains - 117.5
    Float heights are 24mm.
    Fresh intake boots and o-rings.
    Carbs are fully cleaned, with new o-rings, etc.
    Valve clearances are healthy.
    Carbs vacuum synched.

    As I work through the finer adjustments to the pilot circuit, the plugs have been showing color changes that make sense. They move in the right directions as I adjust things.

    For some reason, however, the No. 1 plug frequently shows up much richer than the other three. I suppose I can just alter the pilot screws on that carb to bring it into line, but why would that happen generally apart from strange luck?

    FWIW - I don't leave the bike on the side stand for any significant period of time. Unless I am stopping for a short break, it's always on the center stand.

    #2
    Does #1 show a blue flame with the Colortune?
    79 GS1000S
    79 GS1000S (another one)
    80 GSX750
    80 GS550
    80 CB650 cafe racer
    75 PC50 - the one with OHV and pedals...
    75 TS100 - being ridden (suicidally) by my father

    Comment


      #3
      Originally posted by hampshirehog View Post
      Does #1 show a blue flame with the Colortune?
      It does, but I cannot test way that under load.

      Comment


        #4
        Your Colortune can't lie. Have you had a go at running the bike on 2 or 3 cylinders with the throttle stop wound in a bit to keep it from stalling? You can take the carbs nearly to the cutaway using this trick and it will confirm your pilot circuit as more than just at idle.
        79 GS1000S
        79 GS1000S (another one)
        80 GSX750
        80 GS550
        80 CB650 cafe racer
        75 PC50 - the one with OHV and pedals...
        75 TS100 - being ridden (suicidally) by my father

        Comment

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