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Hiccup at idle speed

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  • #1

    Hiccup at idle speed

    Have this for some time. Really noticed that the #4 cylinder is not backfiring but is expelling gas (as in air) back out the pod filter yesterday. Went for a ride around the block to test my speedo and felt it against my leg (was wearing shorts-yeah I had a helmet on). This happens cold or hot and is irregular and only at idle speeds without any load. It runs like a scalded dog and there is no backfire or ignition of unburned gas in pipes. Any ideas?
    '81 1100 MNS - "Midnight XSpress"
    Original except:
    120 mains outer cylinders - 125 mains inner cylinders - Ceramic headers - Powder coated pipes, covers calipers, and MC's
    4 pods - Air box gutted--E3 Plugs - High Back seat - Grooved out swing arm - SS brake lines
    Fork brace - 160 speedo - Auto CCT
    All gold paint and chrome replaced with GOLD plate
    "STUPID is Forever" Ron White.
    Contact me by PM -I don't deal with stupid anymore.

    Big John
    Tags: None
  • #2
    Possible #4 intake valve shim a bit much not allowing valve to completey close tight, but not noticable at higher rpms? Just a thought......
    81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

    Comment

    • #3
      I finally adjusted my valves after 4 years and found 3 tight valves. I did a leakage test and it was good, only with some leakage around the rings. My compression was 90 on #4 before the valve adjustment and 150psi after.
      "We are often so caught up in our destination that we forget to appreciate the journey." "

      Comment

      • #4
        Had the same problem with the same carb when I bought my bike. In my case it was a bent idle screw tip and found a second rubber "O-ring" in there. I took the carbs off checked all the idle screws and had a good look for a stuck "o-ring" . Worked fine after that.
        BDF Special
        80SG Vetter bagger 1196 Wiseco big bore kit, Mega Cycle Cams, slotted cam gears, ported and flowed head, bronze intake seats, Dyno Jet kit, Dyno coils and Mikes XS air pods, Venture cam chain adjuster,Geezer's regulator, Clutch mod, Mac 4 into 1 with custom built and tuned baffle, Oil cooler,MikesXS emulators mod.
        Dyno tuned to 98 hp at the rear wheel.

        Comment

        • #5
          Thanks, will check!

          I had done the valves and carbs last year. I am pretty sure the carbs are fine but there is the probability that I set the shims too tight. I did the work prior becoming a member and am fairly certain I set them close before finding out loose is better. What is the chance of carbon buildup creating this issue?
          '81 1100 MNS - "Midnight XSpress"
          Original except:
          120 mains outer cylinders - 125 mains inner cylinders - Ceramic headers - Powder coated pipes, covers calipers, and MC's
          4 pods - Air box gutted--E3 Plugs - High Back seat - Grooved out swing arm - SS brake lines
          Fork brace - 160 speedo - Auto CCT
          All gold paint and chrome replaced with GOLD plate
          "STUPID is Forever" Ron White.
          Contact me by PM -I don't deal with stupid anymore.

          Big John

          Comment

          • #6
            Carbon build up could be a possibility if it runnin' extremely rich for some time but IMO unlikely as I don't gather from any of your older post that you "lug" it around or that has been a issue prior. Think we're all just throwing out some possible causes at this point.
            81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

            Comment

            • #7
              Yeah you're right,

              Only remember 1 hardley ever passed me! I didn't want to dump my passenger (newbie) but it sure was hard letting him go!
              '81 1100 MNS - "Midnight XSpress"
              Original except:
              120 mains outer cylinders - 125 mains inner cylinders - Ceramic headers - Powder coated pipes, covers calipers, and MC's
              4 pods - Air box gutted--E3 Plugs - High Back seat - Grooved out swing arm - SS brake lines
              Fork brace - 160 speedo - Auto CCT
              All gold paint and chrome replaced with GOLD plate
              "STUPID is Forever" Ron White.
              Contact me by PM -I don't deal with stupid anymore.

              Big John

              Comment

              • #8
                LOL.....can tell you haven't forgot that incident!
                81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

                Comment

                • #9
                  Bad exhaust systems can make that happen at certain rpms. It will turn the carb black inside as well...
                  Skids (Sid Hansen)

                  Down to one 1978 E. Stock air box with K&N filter, 81H pipes and carbs, 8500 feet elevation.

                  Comment

                  • #10
                    Thanks Skids,

                    But bad as in holes? Blasted these and they looked very good. Just ceramic coated em' and installed with new gaskets and can't be certian but they appear even in back pressure. Almost positive that the hiccup is only #4.
                    No discoloration in carbs (running pods so was easy to check).
                    Last edited by jmnjrpa; 05-07-2010, 02:40 PM. Reason: added
                    '81 1100 MNS - "Midnight XSpress"
                    Original except:
                    120 mains outer cylinders - 125 mains inner cylinders - Ceramic headers - Powder coated pipes, covers calipers, and MC's
                    4 pods - Air box gutted--E3 Plugs - High Back seat - Grooved out swing arm - SS brake lines
                    Fork brace - 160 speedo - Auto CCT
                    All gold paint and chrome replaced with GOLD plate
                    "STUPID is Forever" Ron White.
                    Contact me by PM -I don't deal with stupid anymore.

                    Big John

                    Comment

                    • #11
                      Originally posted by Winterhawk View Post
                      I finally adjusted my valves after 4 years and found 3 tight valves. I did a leakage test and it was good, only with some leakage around the rings. My compression was 90 on #4 before the valve adjustment and 150psi after.
                      I'm gonna say start with a comptession test and see if you come up with one or more cylinders low.
                      Flatlander

                      '81 XS11H

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