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  • #1

    Carbs are giving me fits.

    I have a 1979 xs 1100 special i have gone threw the carbs and sinked them and adjusted them. The bike runs good my issue is now it won't idle initially ( seems too low and acts like it wants to stall) but after you have been riding it the idle will hang around 2500 for a while then eventually come down. I had the bike idling fine before i sinked the carbs but now the carbs are sinked and the thing is giving me fits. what to do i have also adjusted the pilot screws to 1 turn thinking that it was to rich at idle. the book calls for 1 1/4 turns out. anyone with any ideas
    Spooky

    A thing of beauty is a joy forever

    11/1978 SX 1100 Special SF black metallic 59,000+ miles still kickin
    850 FD Mod
    Tags: None
  • #2
    Hanging idle usually means to lean.
    Nathan
    KD9ARL

    μολὼν λαβέ

    1978 XS1100E
    K&N Filter
    #45 pilot Jet, #137.5 Main Jet
    OEM Exhaust
    ATK Fork Brace
    LED Dash lights
    Ammeter, Oil Pressure, Oil Temp, and Volt Meters
    Green Monster Coils
    SS Brake Lines
    Vision 550 Auto Tensioner

    In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

    Theodore Roosevelt

    Comment

    • #3
      Three things I can think of will cause the hanging idle, well maybe four.

      1 Need to synch carbs, which you said has been done, but if you tuned the mixtures since, you will want to repeat the synch.

      2 Vacuum leak, if you have a vac leak around the throttle plates or the intake boots it can cause a hnging idle, but that would not go away.

      3 Lean mixture like Nate mentioned, and what you stated as to mixture screw settings may well be the cause.

      4 Would be the dreaded sticking throttle cable.

      Hope that helps you some.
      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

      Comment

      • #4
        The initial idle and the hanging idle point me in the direction that DGXSER has said as well as Nate. Personally I would be inclined to look at the mixture screws first in this situation.
        2-79 XS1100 SF
        2-78 XS1100 E Best bike Ever
        80 XS 1100 SG Big bore kit but not fully running yet.
        Couple of more parts bikes of which 2 more will live!

        Comment

        • #5
          Thanks for the advice

          I will try the idle screws i never would have guessed. I will post the results and let you know thanks again.
          Spooky

          A thing of beauty is a joy forever

          11/1978 SX 1100 Special SF black metallic 59,000+ miles still kickin
          850 FD Mod

          Comment

          • #6
            jat, did u use vac guages 2 do the carb sync? If so did u calibrate the guages?
            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]

            Comment

            • #7
              i zeroed out the guages before i used them . the first time i did the sink the darn thing had a flutter before 2200 rpm's but it would idle fine.... Now it runs great no flutter but this idle thing. is just odd
              Spooky

              A thing of beauty is a joy forever

              11/1978 SX 1100 Special SF black metallic 59,000+ miles still kickin
              850 FD Mod

              Comment

              • #8
                I like DGSXER's list. Mine did the same thing. The carb boots were horribly bad. Didn't show up until it warmed up. Can't remember what I sprayed to find them, but when the idle ran up it was pretty obvious. Plus, like most here, I found the book settings on the mixture screw was way too lean.
                Keep at it.You'll get it.
                Bothell, WA
                1980 XS1100SG

                Comment

                • #9
                  Originally posted by greatnw View Post
                  I like DGSXER's list. Mine did the same thing. The carb boots were horribly bad. Didn't show up until it warmed up. Can't remember what I sprayed to find them, but when the idle ran up it was pretty obvious. Plus, like most here, I found the book settings on the mixture screw was way too lean.
                  Keep at it.You'll get it.
                  The "book" setting on the mixture screws is nothing more than the place to start adjusting from, not the place to run them at. You need somewhere to start adjusting from when starting with an unknown carb setup, and that's what the "book" setting is. You need to use one of the several methods for determining the correct setting for the idle mixture screw for EACH cylinder as part of the sync process. If you don't do this, you have not REALLY done a sync, you have only done PART of one.
                  Cy

                  1980 XS1100G (Brutus) w/81H Engine
                  Duplicolor Mirage Paint Job (Purple/Green)
                  Vetter Windjammer IV
                  Vetter hard bags & Trunk
                  OEM Luggage Rack
                  Jardine Spaghetti 4-2 exhaust system
                  Spade Fuse Box
                  Turn Signal Auto Cancel Mod
                  750 FD Mod
                  TC Spin on Oil Filter Adapter (temp removed)
                  XJ1100 Front Footpegs
                  XJ1100 Shocks

                  I was always taught to respect my elders, but it keeps getting harder to find one.

                  Comment

                  • #10
                    Originally posted by Spookysxs11 View Post
                    i zeroed out the guages before i used them . the first time i did the sink the darn thing had a flutter before 2200 rpm's but it would idle fine.... Now it runs great no flutter but this idle thing. is just odd
                    Zeroing the guages isnt calibrating them unfortunately, u need a vaccuum source, a mity vac works well if u have 1 or i use the engine, whilst the engine is running use the same inlet barb and connect 1 hose at a time to the same barb and note the readings on each guage adjust accordingly, once adjusted the guages wont neccesarily show zero when disconnected. Calibrate ur guages, give it another sync and hopefully that will solve ur problem.
                    Last edited by petejw; 08-13-2011, 07:34 PM.
                    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]

                    Comment

                    • #11
                      not sure what to do??

                      I adjusted the screws out 1 1/2 turns and still the same thing although it is better. should i continue to adjust out untill it is good ?? the carb boots last time i checked are not leaking. I will check again tomorow. let me know any other ideas. do you think it is mechanical??
                      Spooky

                      A thing of beauty is a joy forever

                      11/1978 SX 1100 Special SF black metallic 59,000+ miles still kickin
                      850 FD Mod

                      Comment

                      • #12
                        Originally posted by Spookysxs11 View Post
                        I adjusted the screws out 1 1/2 turns and still the same thing although it is better. should i continue to adjust out untill it is good ?? the carb boots last time i checked are not leaking. I will check again tomorow. let me know any other ideas. do you think it is mechanical??
                        As I mentioned, the book setting is just a starting point. The proper way to set the idle mixture is to adjust the idle mixture on each carb for the highest idle speed, then turn the screw in till the idle speed just starts to drop again. You do this for each carb, and once this is done the idle mixture should be pretty close to right where it should be. If you need to go more than about 4 turns out, you may need to go up a size on your idle jets or you might have clogged idle passages. But it's very important to do a proper idle mixture adjustment, the bike will exhibit strange running characteristics until you do.
                        Cy

                        1980 XS1100G (Brutus) w/81H Engine
                        Duplicolor Mirage Paint Job (Purple/Green)
                        Vetter Windjammer IV
                        Vetter hard bags & Trunk
                        OEM Luggage Rack
                        Jardine Spaghetti 4-2 exhaust system
                        Spade Fuse Box
                        Turn Signal Auto Cancel Mod
                        750 FD Mod
                        TC Spin on Oil Filter Adapter (temp removed)
                        XJ1100 Front Footpegs
                        XJ1100 Shocks

                        I was always taught to respect my elders, but it keeps getting harder to find one.

                        Comment

                        • #13
                          First thing to rule out is the vacuum leak. Take soem carb cleaner or WD40 or starting fluid, or even an unlit propane torch. whatever the source, move it around each carb and inlet boot listenign to the engine as it idles. If the idle jumps when you hit a certain spot, there is your vacuum leak. If you have a vacuum leak, everything else is futile really.
                          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

                          Comment

                          • #14
                            I found that the Colortune was the secret to getting the idle just right.

                            There are plenty of folk on this site who swear by it. I bought mine simply because so many raved about the difference it made to performing what is quite a tricky task.

                            http://www.xs11.com/xs11-info/tech-t...rburetors.html
                            Melbourne, Australia. XS1100RH

                            Comment

                            • #15
                              [QUOTE=melbxs;337665]I found that the Colortune was the secret to getting the idle just right.

                              There are plenty of folk on this site who swear by it. I bought mine simply because so many raved about the difference it made to performing what is quite a tricky task.

                              These videos on Colortuning are pretty interesting think I will give this a try

                              http://www.youtube.com/watch?v=5BU-5...eature=related

                              http://www.youtube.com/watch?v=cy_ya...eature=related

                              http://www.youtube.com/watch?v=6hFUvQ4gaPc

                              http://www.youtube.com/watch?v=USb3M-MQYXU

                              Comment

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