Carb problem

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  • jwhelan65
    • Jan 2026

    #1

    Carb problem

    1980 750 E, carbs cleaned and re-built, new petcock,

    Will only run on choke????

    Any ideas?
  • Nessism
    Forum LongTimer
    GSResource Superstar
    Past Site Supporter
    Super Site Supporter
    • Mar 2006
    • 35787
    • Torrance, CA

    #2
    Have the carbs been vacuum synced? Pilot jets held up to a light to make sure they are open? How is the coil voltage?
    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

    • Gonzo

      #3
      It ran fine before hand? No changes to exhaust or air intake (i.e. pods/air box change)? I really have no input, but just want to point out that some backgroudn info would really help someone who has a clue.

      Comment

      • jwhelan65

        #4
        Yanked the carbs back off...second time

        Comment

        • TPL

          #5
          Only running through the enricher circuit tells me possibly idle screw backed of to far during the cleaning process, a guess.

          Comment

          • Nessism
            Forum LongTimer
            GSResource Superstar
            Past Site Supporter
            Super Site Supporter
            • Mar 2006
            • 35787
            • Torrance, CA

            #6
            Originally posted by TPL
            Only running through the enricher circuit tells me possibly idle screw backed of to far during the cleaning process, a guess.
            Na, you can open them tons and it won't act any differently than 4 turns - will will run decently.
            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

            • TPL

              #7
              Originally posted by Nessism
              Na, you can open them tons and it won't act any differently than 4 turns - will will run decently.
              I was referring to the idle adj screw to the linkage.

              Sounds strange that all pilots would be clogged after cleaning them, but if the idle linkage is some how way off, could be the reason, no? It would still run through the enricher circuit though.

              Comment

              • jwhelan65

                #8
                dunno it is frustrating the hell out of me..

                Comment

                • jwhelan65

                  #9
                  Ok it fires up but surges during idle? I road it down the street and it boggs at higher rpm's. Pulled the carbs and checked, every thing looks good...I dunno?

                  Comment

                  • Guest

                    #10
                    I also agree that the main idle screw to the linkage could be the problem. As TPL stated above, it could be backed out a little too far. I had the same thing happen to me on my second carb rebuild. I've done 4 carb rebuilds now and since I made the idle screw mistake the one time, I make sure to double check that before I put them back on.

                    Nothing more frustrating/embarassing than to be pounding your chest after a carb rebuild and saying "I know I did these right and they're gonna be awesome now!!!!" and then not have the bike turn over...awkward...

                    Comment

                    • TheCafeKid

                      #11
                      You make sure the air jets were clean? Lotsa people break down carbs forget about the airjet. Then when they put em back together that Berrymans will turn to goo and clog em up. Can't run if it can't breathe. Did ya look at the plugs when turning the motor over? If it won't fire and they're wet it's likely not gwttig enough air.

                      Comment

                      • jwhelan65

                        #12
                        Originally posted by TheCafeKid
                        You make sure the air jets were clean? Lotsa people break down carbs forget about the airjet. Then when they put em back together that Berrymans will turn to goo and clog em up. Can't run if it can't breathe. Did ya look at the plugs when turning the motor over? If it won't fire and they're wet it's likely not gwttig enough air.
                        By airjet you mean what? the one at the frot of the carb body that has a small plug from the factory in it?

                        Comment

                        • BigD_83
                          Forum Sage
                          Past Site Supporter
                          • May 2011
                          • 4872
                          • Vancouver

                          #13
                          Won't run withOUT the choke, surges at idle, bogs at higher rpm...sounds like it is getting intermittent high fuel loading at low rpm, and possibly starving for fuel at high rpm.

                          You say it ran well before the carb cleaning, with none of these symptoms...is there a difference in the way it runs on PRIME versus ON? Are you getting any backfire?

                          Again, no input to the problem yet....just digging for a bit more information
                          Last edited by BigD_83; 06-27-2011, 01:27 AM. Reason: miswording fix, left OUT off without.
                          '83 GS650G
                          '83 GS550es (didn't like the colours in the 80's, but they've grown on me)

                          Comment

                          • jwhelan65

                            #14
                            Originally posted by BigD_83
                            Won't run with the choke, surges at idle, bogs at higher rpm...sounds like it is getting intermittent high fuel loading at low rpm, and possibly starving for fuel at high rpm.

                            You say it ran well before the carb cleaning, with none of these symptoms...is there a difference in the way it runs on PRIME versus ON? Are you getting any backfire?

                            Again, no input to the problem yet....just digging for a bit more information
                            Has never run right since I got it, no backfires, tank is clean, fresh gas, new petcock, new plugs, new battery, swapped out the R/R, Good spark, good OHM readings at the signal generator, carbs cleaned,....

                            Comment

                            • TheCafeKid

                              #15
                              Looking the carb throat, airbox side there should be a jet there, assuming we are talking about BS32SS carbs. Guessing it will be a 150. Around the same size in diameter as the main jet. I don't recall ever seeing a set of GS carbs where that jet was plugged but then again I haven't seen them all either.

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