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  • Carburetor Questions/Help

    1980 XS1100SG
    No OCTY and Cone Filters
    I just want to get the bike running decently before fine tuning the jets to the cone filters. I have rebuilt a set of XJ carbs (unknown year). I ruined the original set of pilot jets (no holes) and replaced them with 42.5(s) with holes. I also have a set of 79 XS carbs which I have also gone through.
    1) What causes idle creep, more so when warm? It will creep up fast and high.
    2) What is an easy/simple to set the bowl floats? I am not comfortable with how I have set them and to the measurements.
    3) Recommended measurement for the above XJ and XS?
    4) Recommended turns out for the idle screws for the above XJ and XS?
    5) I set the butterflys via the bread tie method.
    Enough for now and any suggestions are much appreciated.
    Anyone near Tampa that is good with carburetors?
    gene in Tampa, FL

  • #2
    See below
    1) What causes idle creep, more so when warm? It will creep up fast and high. Vacuum leak and out of sync.
    2) What is an easy/simple to set the bowl floats? I am not comfortable with how I have set them and to the measurements. I use the tube method described in the book. Takes a little more time but you know exactly were they are as you can see it in the tube. Using this method on the bench also will show you if you have a leaking needle valve and which float is causing the problems before you have the carbs back on the bike.
    3) Recommended measurement for the above XJ and XS? See # 2
    4) Recommended turns out for the idle screws for the above XJ If you mean idle mixture adjustment screws 1.5 is a good place to start. Sync with sticks, adjust to smooth idle then re-sync.
    5) I set the butterflys via the bread tie method. Good enough for starters but sync with sticks is much better. If the idle is creeping up and that gets worse when the bike is warm I'd think high float level or leaking needle valve. Search the site for vacuum leaks and several methods for finding them will come up. if you suspect that's the problem. Good luck and stay with it. It can be done as we have all been there.



    wingnut
    81 SH (Daily Ride)
    81 650XJ (Brother in laws bike, Delivered)
    81 650XJ Jane Doe (Son's Ride)
    82 750XJ Project bike (Son in law's future ride)
    81 XS 400

    No man has a natural right to commit aggression on the equal rights of another; and this is all from which the laws ought to restrain him.”

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    Thomas Jefferson

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    • #3
      I use a cheep micromiter.
      Extend leg down to 25mm for the early carbs
      23mm down for the XJ

      Remove float bowl gasket if stuck to carb and measure from there.
      Check both sides of float. Holes in float tang for tweaking floats.

      Most likely your RPM shooting up is from needing to be vac synked.

      Since you have individual filters might start pilot screws out 2 to 2 1/2 turns.

      Most likely will be running lean. Might try setting floats 1/2 mm lower...then may need re-jetting.

      mro

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