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81LH Sputters Between 5k and 6k

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  • 81LH Sputters Between 5k and 6k

    Hi everyone, I've got an 81LH that sputters under load between 5k and 6k rpms. It doesn't do it when I rev the bike in neutral, just under a load and if I get over the 6k - 6.5k mark it goes away and revs smoothly through the rest of the rpm range. I just pulled the carbs and cleaned them this weekend. I get a little better throttle response, but the sputter is still there. Any thoughts on where to begin?
    Current Ride:
    81 XS1100LH Midnight Special
    Tkat Fork-Brace
    Previously Owned:
    79 XS750 Special

  • #2
    Hey there,

    Okay, a few questions about the bike. OEM intake/exhaust or mods?

    If it were an earlier model, I would be saying to check your pickup coil wires, but being an 81, the PU wires don't flex as much because the cent. adv. curve is programmed into the TCI. It still uses a mech. vac. adv. but it doesn't flex the wires as much as the early models.

    You were just inside the carbs, what size pilots and mains?

    T.C.
    T. C. Gresham
    81SH "Godzilla" . . .1179cc super-rat.
    79SF "The Teacher" . . .basket case!
    History shows again and again,
    How nature points out the folly of men!

    Comment


    • #3
      Thibtyson, T.C.,

      It could be the pickup coil wires.

      The '81 still has the vacuum advance so the pickup coil plate moves just as much as the '78 to '80s. In '81 the mechanical advance was eliminated but that only turned the reluctor. The 4RO TCI has pre-mapped electronic RPM based advance curves so it doesn't need the mechanical advance.

      In '82 the XJ11 replaced the vacuum advance and its movable pickup plate with the boost sensor. The 10M TCI has pre-mapped electronic RPM and engine load (vacuum) based advance curves. The XJ11 shouldn't have the pickup coil wire problem unless someone accidentally broke 'em while checking the timing or something... or installed a TCI and the timing guts from an XS11.
      -- 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


      • #4
        Originally posted by 3Phase View Post
        Thibtyson, T.C.,

        It could be the pickup coil wires.

        The '81 still has the vacuum advance so the pickup coil plate moves just as much as the '78 to '80s. In '81 the mechanical advance was eliminated but that only turned the reluctor. The 4RO TCI has pre-mapped electronic RPM based advance curves so it doesn't need the mechanical advance.

        .
        I agree, the wires do flex and can break. Check 'em.
        Skids (Sid Hansen)

        Down to one 1978 E. Stock air box with K&N filter, 81H pipes and carbs, 8500 feet elevation.

        Comment


        • #5
          Topcat, Intake is stock and the exhaust is 4-1. I didn't really pay attention to the jet sizes. I assume they are stock. As to the pickup coil wires, I wiggled them earlier in the riding season and it didn't seem to make much difference. Maybe I'll try them again and see if I can get something to happen while the bike is in gear and under load.
          Current Ride:
          81 XS1100LH Midnight Special
          Tkat Fork-Brace
          Previously Owned:
          79 XS750 Special

          Comment


          • #6
            Thibtyson,

            I don't think you want to mess with the pickup coil wires while the bike's in gear and under load.

            Have you read the Tutorials in the Tech Tips section here on the site?

            Here ya go!:-

            Pick-up Coil Wire Repair


            The Coil Pick-Up Fix

            Ignition Problems - Cylinders Misfiring
            -- 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


            • #7
              Originally posted by thibtyson View Post
              Topcat, Intake is stock and the exhaust is 4-1. I didn't really pay attention to the jet sizes. I assume they are stock. As to the pickup coil wires, I wiggled them earlier in the riding season and it didn't seem to make much difference. Maybe I'll try them again and see if I can get something to happen while the bike is in gear and under load.
              Try to seperate every half inch lightly tugging every half inch.......specificly the white wire,DAMHIK.
              81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

              Comment


              • #8
                Originally posted by motoman View Post
                Try to seperate every half inch lightly tugging every half inch.......specificly the white wire,DAMHIK.
                RACIST!
                Greg

                Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                ― Albert Einstein

                80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                The list changes.

                Comment


                • #9
                  Originally posted by BA80 View Post
                  RACIST!
                  If the all important smoke is kept in the wires, these ole' motors get a bit racey again......
                  81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

                  Comment


                  • #10
                    I'll try the pick-up coil wire check again and see if I missed a spot last time. I'll let you know what I find.
                    Current Ride:
                    81 XS1100LH Midnight Special
                    Tkat Fork-Brace
                    Previously Owned:
                    79 XS750 Special

                    Comment


                    • #11
                      OK, now that the family vacation is complete, I took a minute to do the pickup wire check and everything seems fine. There isn't any spots with shrink tubing on the wires, so I don't think there has been a break in the past, or if there was the PO replaced the wires completely. Where to go from here?
                      Current Ride:
                      81 XS1100LH Midnight Special
                      Tkat Fork-Brace
                      Previously Owned:
                      79 XS750 Special

                      Comment


                      • #12
                        This just crossed my mind. Just before one of my ignition coils went out I had a little sputter when cruising not really noticeable any other time except for occasionally it would misfire just once when idling. Then, one day it just dropped 2 cylinders all of a sudden.

                        JAT.
                        Greg

                        Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                        ― Albert Einstein

                        80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                        The list changes.

                        Comment


                        • #13
                          Pinhole in a slide diaphragm?
                          Try your hardest to be the kind of person your dog thinks you are.

                          You can live to be 100, as long as you give up everything that would make you want to live to be 100!

                          Current bikes:
                          '06 Suzuki DR650
                          *'82 XJ1100 with the 1179 kit. "Mad Maxim"
                          '82 XJ1100 Completely stock fixer-upper
                          '82 XJ1100 Bagger fixer-upper
                          '82 XJ1100 Motor/frame and lots of boxes of parts
                          '82 XJ1100 Parts bike
                          '81 XS1100 Special
                          '81 YZ250
                          '80 XS850 Special
                          '80 XR100
                          *Crashed/Totalled, still own

                          Comment


                          • #14
                            I was installing new clutch springs and noticed a leak in a fuel line just below the right hand petcock. I didn't see it until the bike was running but it spits a reasonable amount of fuel and puts an air bubble in the line. I wonder if the air bubble is causing my stutter? I'm trying to wrap my head around it, the air bubble would enter the octopus and then split out to the 2 right hand carbs, then I guess it would cause those two carbs to run lean for a second. But why would it be around the same rpm every time? I need to fix the lines and see if it helps. Any suggestions on fuel line and where to get 'em?
                            Current Ride:
                            81 XS1100LH Midnight Special
                            Tkat Fork-Brace
                            Previously Owned:
                            79 XS750 Special

                            Comment


                            • #15
                              1/4" Tygon line. You should be able to get it at any parts house.

                              BTW, air bubbles are common and won't cause any problem.

                              I'm fairly certain what your experiencing is ignition related.
                              Greg

                              Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                              ― Albert Einstein

                              80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                              The list changes.

                              Comment

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