Allways the same idle problem

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  • zed313
    • Feb 2026
    #1

    Allways the same idle problem

    Hi,





    I placed my subject here but it's possible that's not the right place.

    First, I want to apologize for my English that I don't quite mastered

    My bike starts well, she has a very good cold idle. She easily revs ! Good, i've no problem ! BUT...


    After 10 minutes, the idle starts down (900-800-700) et then stall. If I go back a little idle, the engine hang to 2000.




    So I commend the idle to 1000, and again the idle starts down (900-800-700- etc...)






    You should know that I changed the o-rings, the boots, i've the stock air box with new filter, my carbs are cleaned (with all o-rings set),
    new coils, new plugs, new condensers, new points, blue spark.

    The thing is i've rebuilt the top head engine (valve seat, valve guide). Just after the valve adjustment, the bike worked very well, even at idle. I made 200 km since, do you believe that this has already moved? ...
    Another thing, I already have two shims 2.15, if it tightens again, how can I do?
    Tags: None
    • gustovh
      Forum Sage
      Past Site Supporter
      • Oct 2006
      • 4995
      • Vernonia
      #2
      Check your float bowls for fuel after it won't idle. Could be the petcock is not working properly.

      V
      Gustov
      80 GS 1100 LT, 83 1100 G "Scruffy"
      81 GS 1000 G
      79 GS 850 G
      81 GS 850 L
      83 GS 550 ES, 85 GS 550 ES
      80 GS 550 L
      86 450 Rebel, 70CL 70, Yamaha TTR125
      2002 Honda 919
      2004 Ural Gear up

        Comment

        • steve murdoch
          Forum Guru
          Past Site Supporter
          • May 2004
          • 8491
          • St. Catharines, On.
          #3
          Also check your gas tank cap.
          If it is not venting properly it starve the fuel flow.
          2@ \'78 GS1000

            Comment

            • Newell33
              #4
              You may also want to check for vacuum leaks. Failure to idle once the RPM drops back down, and the RPM slow to return to idle are classic signs of a vacuum leak. I just fixed leaking carb sync ports on my bike that had similar symptoms. It only showed up when the bike was warm. Check your rubber carb boots for cracks.

                Comment

                • Steve
                  GS Whisperer
                  • Jun 2005
                  • 35925
                  • southwest oHIo
                  #5
                  Have you adjusted the pilot mixture screws? It sounds like they are a bit rich, which is good when the bike is cold, but when it warms up, it is too rich. Gustovh suggested checking the float bowls for gas, I will also suggest removing a spark plug to check the color. If it a case of a rich mixture, they will be black.

                  .
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                  #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
                  #2 son: 1980 GS1000G
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                    Comment

                    • Spyderman
                      #6
                      Originally posted by Steve
                      Have you adjusted the pilot mixture screws? It sounds like they are a bit rich, which is good when the bike is cold, but when it warms up, it is too rich. Gustovh suggested checking the float bowls for gas, I will also suggest removing a spark plug to check the color. If it a case of a rich mixture, they will be black.

                      .
                      reall good advice here^^^^^^

                        Comment

                        • Guest
                          #7
                          it sounds like an air leak to me. With the engine running, spray some carb cleaner onto the inlet hoses and see if it affects the idle speed.

                          Like this.

                          Also you make no mention of balancing the carbs. Has this been done since the head rebuild?

                            Comment

                            • zed313
                              #8
                              Hi,

                              Thanks for reply,

                              I'm pretty sure my problem came from my coils... chinese one's... i've wanted to make economy (40 dollars both)

                              I had a problem to with my petcock, that's ok now

                              Charging system is ok, cap wires are new (NGK), spark plug are new, new battery, timing advance ok, new condensers, new points. All my connections wire are clean, but the engine still continue to lose power (like it was lean) when it warm up. It start again when hot but run on two cylinders...

                              Soooooooooooooooooo, i bought DYNA coils 3 ohms, and now i am going to eat potatoes until the end of the month... i'll buy DYNA ignition later, and my question is : does the DYNA coils run well with the original points ignition ?

                                Comment

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