Go-Go-Puh!

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  • Clone
    • Feb 2026
    #1

    Go-Go-Puh!

    It's not a Gs, but the guys at riding single don't give me any help.
    My single, I won't specify a brand so as not to offend anyone, will pull really well up to around 4500rpm with the throttle wrapped, then cuts out and in and out and in etc, like fuel starvation, but not, when I back off a little it hiccups and starts to pull again. It does this in all gears at all speeds always towards the top of the tach and at full throttle.
    I have cleaned the petcock and put in a new filter, fuel flows quickly.
    the overflow is dry, the aircleaner is clean. All the hoses are attached. The plug is continuously a light beige. Apart from this pain in the ### issue, it runs well. :? :?
    I am thinking to just buy a new carb just to see, but of course would rather not.
    Any ideas?
    Tags: None
    • Jethro
      Forum LongTimer
      Charter Member
      GSResource Superstar
      Past Site Supporter
      • May 2002
      • 17888
      • The only Henniker on earth
      #2
      I'm thinking air leak. I spent a lot of time trying to solve a simaler problem. Had the carbs off every other day, cleaned 'em, re-jetted, etc. It all turned out to be crappy intake manifold boots and clamps. Oh, and I did the WD40 test to check for air leaks and they still didn't show up. When I changed the boots, all was well again.

      You still might have a fuel starvation problem, but make sure to check out your intake boots as well.
      Currently bikeless
      '81 GS 1100EX - "Peace, by superior fire power."
      '06 FZ1000 - "What we are dealing with here, is a COMPLETE lack of respect for the law."

      I ride, therefore I am.... constantly buying new tires.

      "Tell me what kind of an accident you are going to have, and I will tell you which helmet to wear." - Harry Hurt

        Comment

        • KGB
          Forum Guru
          • Nov 2002
          • 7146
          • Wilmington ma
          #3
          Does it have points?

          Could be them bouncing at high rpm.

          I'd go with jethro...it may be sucking air at high rpm.
          Keith
          -------------------------------------------
          1980 GS1000S, blue and white
          2015Triumph Trophy SE

          Ever notice you never see a motorcycle parked in front of a psychiatrist office?

            Comment

            • focus frenzy
              #4
              it would help alot if we knew what it is.
              I think I remember you having a yamaha of some sort.
              does it have yamaha's twin carb?? the second side comes on above 5k rpm! the xt 350 I have had clogged the cross over line that supplys fuel to the jet in the right side and it would run fine up to 5K rpm where the secondary side would come into play and it would fall right on it's face.

              I have also seen a cbr600 do something just like this, it would pull like a raped ape to 6K rpm then fall on its face, it turned out to be the igniton control box, at 6K it changes the advance on the ignition and it would loose fire.

                Comment

                • Clone
                  #5
                  Yes, It is a Yamaha 350. No points, induction pickup. Only one carb a CV. I will examine the intake and airbox boots to look for cracks and spray them down as well. I noticed an abrasion on the diaphragm for the CV slider when I had it apart last time. If this has become a hole would that cause the above problem? :?

                    Comment

                    • lhanscom
                      #6
                      Originally posted by Clone
                      If this has become a hole would that cause the above problem? :?
                      I think if it had become a hole it would run like crap all the time, not just above a certain rpm, but if you have the carb off check it anyway.

                        Comment

                        • Anonymous
                          #7
                          Probable CAUSE of Power Loss and Bike Birth Control

                          Actually, I think a small hole would do just what you are describing on the diaphragm. Dink or Keith Krause - you can check me on this.....

                          Why? The carb runs on the pilot at light throttles. AS you come up, vacuum lifts the CV slide. With a small pinhole, the slide will come up a little less AND a little slower, and there goes midrange and midrange acceleration - too lean condition. THEN, when the vacuum goes way up with wide open throttle and rpms coming up past 6 grand or so, the vacuum more then overcompensates for the small vacuum leak in the diaphragm and voila, your on the mains and pulling hard again.

                          Point bounce would always get worse at a certain RPM or higher I would believe and the bike would not have only a midrange dip like you say.

                          Hold your diaphragm up to a strong light and check for pinholes. And don't say that to your wife. Heh heh. - Dieter

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