Still rough at small throttle openings

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  • sailorman1617
    • Feb 2026

    #1

    Still rough at small throttle openings

    Adjusted valves, new plugs, sync'ed carbs (helped some), airbox sealed, no vacuum leaks I can detect. Better but still stumbles at very small throttle openings, like just off idle starting off and including 5th gear up to about 50, then cleans up as the throttle is opened a bit. Runs great otherwise.

    I'm assuming I need to replace the O-rings and install a stage 1 Dynajet kit. Had to install a Supertrapp 4 into 1 many years ago when the stockers rusted out. Bike ran terrible until I removed one disc, but still lean. The bike was always cold blooded, even when new; I think '82 was the first year they sealed the air adjust screw.? Takes forever to warm up, pops at idle and trailing throttle, which I'd guess is on the idle circuit regardless of rpm (throttle closed that is).

    Any other ideas? Really wish I'd visited here BEFORE I'd rebuilt the carbs
  • tkent02
    Forum LongTimer
    Past Site Supporter
    • Jan 2006
    • 35571
    • Near South Park

    #2
    A DynaJet kit has nothing to do with off idle performance. Which technique did you use to set your mixture screws?

    Tending to the O rings is always a good idea.
    http://img.photobucket.com/albums/v5...tatesMap-1.jpg

    Life is too short to ride an L.

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    • Guest

      #3
      Originally posted by sailorman1617
      Any other ideas? Really wish I'd visited here BEFORE I'd rebuilt the carbs
      Try opening the mixture screws 1/2 a turn. While you are at it, confirm they are all set the same in the first place.


      Mark

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      • sailorman1617

        #4
        mixture screws set at the factory and sealed over. Can't adjust. I believe the stage 1 kit replaces it, supplying a drill bit to 'unseal' it.

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        • jsandidge
          Forum Sage
          Past Site Supporter
          • Jun 2013
          • 1482
          • Norfolk, Virginia

          #5
          You don't need a kit to do that.
          https://drive.google.com/open?id=0B9zH8w8Civs8ejBJWjdvYi1LNTg&resourcekey=0-hlJp0Yc4K_VN9g7Jyy4KQg&authuser=fussbucket_1%40msn.com&usp=drive_fs
          1983 GS750ED-Horsetraded for the Ironhead
          1981 HD XLH

          Drew's 850 L Restoration

          Drew's 83 750E Project

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          • tkent02
            Forum LongTimer
            Past Site Supporter
            • Jan 2006
            • 35571
            • Near South Park

            #6
            Originally posted by sailorman1617
            mixture screws set at the factory and sealed over. Can't adjust. I believe the stage 1 kit replaces it, supplying a drill bit to 'unseal' it.
            No, it needs to be adjusted, and it needs to be removed so you can properly clean the carburetors and replace the O rings on the screws. The other O rings in the carbs are certainly wasted by now too. Any appropriate sized drill bit will do, then a dry wall screw, just screw it in the hole and pull the plug out. The screw is also factory sealed with paint, that needs to be removed too. It's all in the tutorial...... You have seen the carburetor cleaning tutorial, right?
            http://img.photobucket.com/albums/v5...tatesMap-1.jpg

            Life is too short to ride an L.

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            • robertbarr
              Forum Sage
              Past Bard Award Winner
              GSResource Superstar
              • Sep 2005
              • 2721
              • Joliet, Illinois

              #7
              Intake o-rings are an investment in your own sanity.
              and God said, "Let there be air compressors!"
              __________________________________________________ ______________________
              2009 Suzuki DL650 V-Strom, 2004 HondaPotamus sigpic Git'cha O-ring Kits Here!

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              • Big T
                Forum LongTimer
                Past Site Supporter
                Super Site Supporter
                • Mar 2005
                • 12392
                • West Slope, OR

                #8
                Originally posted by sailorman1617
                Any other ideas? Really wish I'd visited here BEFORE I'd rebuilt the carbs

                Yup, because now you need to take those carbs off again and do it correctly.

                Check the CV carb cleaning tutorial, do everything in there and I believe you'll find a huge improvement

                When you rebuilt them did you use kits? Did you save any original parts?
                1978 GS 1000 (since new)
                1979 GS 1000 (The Fridge, superbike replica project)
                1978 GS 1000 (parts)
                1981 GS 850 (anyone want a project?)
                1981 GPZ 550 (backroad screamer)
                1970 450 Mk IIID (THUMP!)
                2007 DRz 400S
                1999 ATK 490ES
                1994 DR 350SES

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                • sailorman1617

                  #9
                  Thanks for the replies. To answer:

                  As I mentioned, I had not seen this website nor Basscliff's carb cleaning tutorial. But having seen that since, the only thing I really missed were the O rings. The jets were replaced with new OEM Suzuki rebuild kits, after cleaning all passages (I use old guitar strings). Not having any instructions, I did NOT separate the carbs, so the O rings on the fuel tubes were not replaced. And yes, I did save the original jets.

                  The stage 1 kit is to get rid of the lean condition after replacing the pipes. The bike was lean when the pipes were replaced, probably 20 years ago, that's not a new condition.

                  I'll probably take care of the sealed air mixture screws when I take care of the O rings and the jet kit. Until then, at least it's running again and other than the mentioned roughness, still a pleasure to ride.

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