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Hanging idle going to stall, NOT carbs. Need ideas.

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    Hanging idle going to stall, NOT carbs. Need ideas.

    I will try to make this long story as short as possible without leaving out important info. '81 GS1100e. I have put about 3000 miles on it, has always had minor fueling issues but it would idle and run OK, a bit rich at full throttle and crappy (30-35) mileage. Problem started when I violated the "Change one thing at a time" rule. List of changes:
    Removed 4-1 and put stock exhaust back on with new gaskets.
    Removed K&N filter and drilled airbox cover, replaced with stock.
    Adjusted valves.
    Changed plugs, replaced caps with correct NGK.
    Set static and dynamic timing (Dyna S with 3 ohm dyna coils).
    Cleaned carbs properly, dip & ultrasonic, o-rings, replaced 115 jets with correct for '81 107.5.
    Verified proper and clean pilot and air corrector jets, float levels, bench and carbtune sync perfect at 2500.
    Problem:
    Starts OK, come off choke and idles OK until it warms up. The hotter it gets the more hangy the idle gets. It will idle at 2200 all day and run fine from 2000-9500RPM. The idle will eventually settle down and keep going down until it stalls. When it stalls it starts right back up, but stutters and misfires until 2000 again. The hotter it gets (96 today) the more it stalls, maybe I have just not noticed before as it hasn't been this hot. I have had the carbs off 3 times. Finally put a set of carbs off a perfectly running '83. Started and idled OK, by the end of a 20 mile ride exactly the same symptoms. Have also tried running on prime. I am running in circles here, need some fresh ideas. The more I work on it, the worse it gets.
    Already checked: Everything. Well, obviously not and maybe I am overthinking this. but it is not a common problem or maybe I am screwing up the same thing over and over. Things I am going to try next: Put K&N back in, check around coils after dark for arcing. Any other ideas? I was thinking Dyna module, but timing mark is steady and fires all plugs with timing light attached. When it stalls it sounds like the motor is trying to turn backwards as it dies and it blows the #4 hose off the carbtune as the vacuum goes to 0. Runs WAY too good to be cam timing. Carb boots look OK but I am going to swap them, airbox boots OK as well although one is missing the metal ring that secures it. Too hot to work on it again until morning, hopefully I will have some fresh ideas....
    Last edited by bobgroger; 08-19-2016, 08:24 PM. Reason: spelling :(
    sigpic
    09 Kaw C14 Rocket powered Barcalounger
    1983 GS1100e
    82\83 1100e Frankenbike
    1980 GS1260
    Previous 65 Suzuki 80 Scrambler, 76 KZ900, 02 GSF1200S, 81 GS1100e, 80 GS850G

    #2
    Have you changed your Boot O-rings or boots? It's a common place for vacuum leaks.
    http://www.thegsresources.com/_forum...ine=1440711157'78 GS1000E, Dyna-S ignition, Dyna Green Coils, K&N pods, Delkevic SS 4-1 exhaust, Dynojet Stage 3 jet kit, Russell SS Brake Lines, Progressive suspension, Compu-Fire series Regulator 55402 and Advmonster cree LED headlight conversion.

    Comment


      #3
      Originally posted by OldVet66 View Post
      Have you changed your Boot O-rings or boots? It's a common place for vacuum leaks.
      No o-rings on 16-valve motors. I have not changed them but swapping with the bike I borrowed the carbs from is on the list. They are very pliable.
      sigpic
      09 Kaw C14 Rocket powered Barcalounger
      1983 GS1100e
      82\83 1100e Frankenbike
      1980 GS1260
      Previous 65 Suzuki 80 Scrambler, 76 KZ900, 02 GSF1200S, 81 GS1100e, 80 GS850G

      Comment


        #4
        How many turns open are the pilot screws?
        Ed

        To measure is to know.

        Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

        Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

        Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

        KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

        Comment


          #5
          Originally posted by Nessism View Post
          How many turns open are the pilot screws?
          Original carbs tried 0-4 turns, 83 carbs are 3.5 and ran great on other bike
          sigpic
          09 Kaw C14 Rocket powered Barcalounger
          1983 GS1100e
          82\83 1100e Frankenbike
          1980 GS1260
          Previous 65 Suzuki 80 Scrambler, 76 KZ900, 02 GSF1200S, 81 GS1100e, 80 GS850G

          Comment


            #6
            One thing to do is lube your mechanical spark advance unit. If that doesn't do it I'd start looking for vacuum leaks. Maybe replace the rubber carb runners even though the old ones seem okay. There could be a crack somewhere you don't recognize. Also check the petcock vacuum line and even the petcock diaphragm. A hanging idle is more often than not the result of a vacuum leak.
            Ed

            To measure is to know.

            Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

            Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

            Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

            KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

            Comment


              #7
              Cap off the vacuum line on #2 carb and run petcock on PR to rule it out.
              1981 gs650L

              "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

              Comment


                #8
                Maybe you over-adjusted a valve rocker, so the valve don't quite shut?
                Or a poorly seated valve?
                Check the compression after the engine is hot..
                1982 GS1100G- road bike
                1990 GSX750F-(1127cc '92 GSXR engine)
                1987 Honda CBR600F Hurricane

                Comment


                  #9
                  Sorry I can not offer any advice on this subject. I am following along to find the cause of your hanging idle as I am fighting the same thing. Have just gone through my carbs again looking for the cause but as yet I have not found any trouble spots.
                  Do keep us posted when you learn what it will take to fix yours.
                  Thanks
                  Larry

                  '79 GS 1000E
                  '93 Honda ST 1100 SOLD-- now residing in Arizona.
                  '18 Triumph Tiger 800 (gone too soon)
                  '19 Triumph Tiger 800 Christmas 2018 to me from me.
                  '01 BMW R1100RL project purchased from a friend, now for sale.

                  Comment


                    #10
                    I would again double check for leaks.

                    but also I just had a similar issue and it ended up being a bad spark sender in the dyna s. So it it would start up somewhat crappy. But it would end up dying because one of the lobes ended up being faulty. I would give the dyna s a test

                    Comment


                      #11
                      Almost every time I have issues with a bike that has a dyna s on it, it's the dyna s that is failing. I've bought more than one that was faulty out of the box. I no longer use them, to me they aren't worth the headache.

                      Comment


                        #12
                        The OP sounds like he knows what he is doing but there is another thing that isn't mentioned. Most hanging idle issues are dirty pilot circuits or pilot jets. I always change the pilot jets as I don't care to attempt cleaning with a little wire or something of the like. Also, if the throttle cable is adjusted too tight, the idle can hang. You should be able to take your finger and deflect the cable where it is between the cable holding bracket and the place where the barrel inserts into the bellcrank and deflect the cable a bit... in other words it should have a bit of slack. Easy to check.

                        Comment


                          #13
                          All great suggestions, I am going to eliminate as many as I can before it gets too hot today. Also learned the pros use propane to hunt down vacuum leaks so I am going to wave my torch around the carbs and see if the idle improves. Also going to hook the carbtune back up and see if one cylinder is markedly different with the known good carbs, that may help isolate the bad cylinder. Might also run to Radio Shack and get a can of freeze spray so I can cool down the Dyna modules when it acts up. I have to remember owning old bikes is an adventure....
                          sigpic
                          09 Kaw C14 Rocket powered Barcalounger
                          1983 GS1100e
                          82\83 1100e Frankenbike
                          1980 GS1260
                          Previous 65 Suzuki 80 Scrambler, 76 KZ900, 02 GSF1200S, 81 GS1100e, 80 GS850G

                          Comment


                            #14
                            Originally posted by DohcBikes View Post
                            Almost every time I have issues with a bike that has a dyna s on it, it's the dyna s that is failing. I've bought more than one that was faulty out of the box. I no longer use them, to me they aren't worth the headache.
                            What are you buying as a replacement to Dyna?
                            Rob
                            1983 1100ES, 98' ST1100, 02' DR-Z400E and a few other 'bits and pieces'
                            Are you on the GSR Google Earth Map yet? http://www.thegsresources.com/_forum...d.php?t=170533

                            Comment


                              #15
                              What about that missing carb boot clamp?
                              Seems like air could get around that?
                              Maybe try the stock ignitor/mechanical advance on the 83 bike and see what happens.
                              Hopefully the Dyna rotor magnet doesn't look like this
                              GS\'s since 1982: 55OMZ, 550ES, 750ET, (2) 1100ET\'s, 1100S, 1150ES. Current ride is an 83 Katana. Wifes bike is an 84 GS 1150ES

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