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  • Minds Needed For A Question

    For the last 2 weeks since I've been riding and working on my 1978 XS1100 with 36,000 miles. I've been stumped. I've spent about 40 hours on the XS1100 trying to figure out why the number 4 plug is dark and pretty much dry black. I've replaced the choke valve even. I pulled the exhaust hoping to find the exhaust port plugged. Nope. The decided to once again pull the carbs for the 15th time probably. What I found was the sync tube has slipped into the intake about 1 inch. Would this cause it to want to suck in extra fuel or restrict air? Bernoulli's Principle? A 1/4 inch tube 1 inch into the intake would have what effect? Can't ride it yet and need to bead blast the plug off first to see if this fixed it. It would also cut out and sputter at a 4 to 5 thousand rpm band with some throttle opening up. I think that this is the result of to much fuel gong into the 4 cylinder. Carbs are perfect. Compression is 160 warm. pickups good. fuel visible at 3 mm before joining surface with the float height set at 25mm. The other 3 plugs are clean. Even traded the 1 for 4 plugs wires so ruled this out. This bike was built at Merriam Cycle about 6 years ago and has performed great till now.

    If this fixed it then we all could learn from this as it could happen to others. I think my tube pulled out a while back and I pushed it back in without comparing the height against the other 3
    "We are often so caught up in our destination that we forget to appreciate the journey." "

  • #2
    Sound to me like

    you should consider replacing those intakes.....JAT
    1980 XS11 Special aka The Monster
    "My life used to be a Soap Opera, until I realized something, I own the network."
    My Photo Bucket

    Comment


    • #3
      if anything that would probably cause it to run lean,
      as it would want to suck in air, id pull it back up and put
      some sealant around it.
      Is the engine blowing smoke or burning oil?, im running
      my parts engine atm which has worn rings, either 1 or 4 would foul, if i had it running on the rich side.
      pete


      new owner of
      08 gen2 hayabusa


      former owner
      1981 xs1100 RH (aus) (5N5)
      zrx carbs
      18mm float height
      145 main jets
      38 pilots
      slide needle shimmed .5mm washer
      fitted with v/stax and uni pod filters

      [url]http://www.youtube.com/watch?v=3pA8dwxmAVA&feature=mfu_in_order&list=UL[/url]

      Comment


      • #4
        Needle position? I had a similar issue with one a while ago. Mine are the 81 models with non adjustable needles. I had put the needle back in the wrong order (spring and washer on wrong side). Corrected that and the issue went away.
        Life is what happens while your planning everything else!

        When your work speaks for itself, don't interrupt.

        81 XS1100 Special - Humpty Dumpty
        80 XS1100 Special - Project Resurrection


        Previously owned
        93 GSX600F
        80 XS1100 Special - Ruby
        81 XS1100 Special
        81 CB750 C
        80 CB750 C
        78 XS750

        Comment


        • #5
          Hmmmm ...

          Seems unlikely that the needle position could have changed unless you've had that slide assy. apart and if so; recheck it.

          But ... jet needles do wear ... that may cause it to run slightly rich.
          80G Mini-bagger
          VM33 Smooth bores, Pods, 4/1 Supertrapp, SS brake lines, fork brace

          Past XS11s

          79F Stone stocker and former daily driver, sold May '10 now converting for N.O. to cafe style
          79SF eventually dismantled for parts
          79F Bought almost new in 80, sold for a house
          79F The Ernie bike sold to a Navy dude summer 08
          79SF Squared-off Special, Vetter/Bates tour pkg., Mikes XS coils, G rear fender and tail light. Sold June 09

          Comment


          • #6
            I was wondering if the tube in the intake could increase the velocity thus pulling the slide up sooner and or farther then the other 3 at given RPM and maybe coloring the plug. It's not the rings and it passed the leakage test with the same as the other 3 which are white. New jets and swapped the needle in #4 to be sure. Raining to hard to test ride it and will for the next 3 days.
            "We are often so caught up in our destination that we forget to appreciate the journey." "

            Comment


            • #7
              seems unlikely to me that ...

              the loose tube could do that... I think it might cause a lean condition instead.

              I think you could try to fire it without the airbox while watching the slides though, if you thought they were not all lifting equally.

              Are the float valves all new or have you swapped any of them out yet?... and no chance of a slightly fuel-loaded float, right?

              A few of us have had loaded floats before.
              80G Mini-bagger
              VM33 Smooth bores, Pods, 4/1 Supertrapp, SS brake lines, fork brace

              Past XS11s

              79F Stone stocker and former daily driver, sold May '10 now converting for N.O. to cafe style
              79SF eventually dismantled for parts
              79F Bought almost new in 80, sold for a house
              79F The Ernie bike sold to a Navy dude summer 08
              79SF Squared-off Special, Vetter/Bates tour pkg., Mikes XS coils, G rear fender and tail light. Sold June 09

              Comment


              • #8
                I did run it with thhe airbox off on the lift. They all moved fine. The tube is very tite. I had to sqeeze pretty had with channel locks to get it back into the hieght it should be. It runs awsome on the lift. Just the black dry coating on #4. No leakage at the tube.

                I think the mixture going around the 1/4 inch tube causes an increase in vellocity. Like more fuel mixture. Maybe it affects the slide diaphram height pulling more fuel from thhe needles some how. We will find out when ever I get to ride it.
                "We are often so caught up in our destination that we forget to appreciate the journey." "

                Comment


                • #9
                  It's the best set of carbs I've ever built. I even check the fuel level height on the outside using see through tubing. New needles and seats. All jets, floats and other parts are mostly new Mikuni. The compression on number 4 was somewhat higher then the other 3. Hot, I got a reading of 168psi. I thought it was carbon build up causing higher compression level over 158psi that the other 3 registered at.
                  "We are often so caught up in our destination that we forget to appreciate the journey." "

                  Comment


                  • #10
                    see what you're sayin about the tube now ...

                    Maybe it is carbon ... while you're waiting for the rain to stop, maybe pour an oz of MMO down that hole and let is soak for a few days ??? That stuff eats built up carbon good.
                    80G Mini-bagger
                    VM33 Smooth bores, Pods, 4/1 Supertrapp, SS brake lines, fork brace

                    Past XS11s

                    79F Stone stocker and former daily driver, sold May '10 now converting for N.O. to cafe style
                    79SF eventually dismantled for parts
                    79F Bought almost new in 80, sold for a house
                    79F The Ernie bike sold to a Navy dude summer 08
                    79SF Squared-off Special, Vetter/Bates tour pkg., Mikes XS coils, G rear fender and tail light. Sold June 09

                    Comment


                    • #11
                      Put clean plugs in 1 and 4, switch plug wires and see if it switches problem to no 1. May not be a fuel problem
                      79SF
                      XJ11
                      78E

                      Comment


                      • #12
                        It might be ... Dry carbon Fouling This is from NKGs site on plug conditions.

                        They show a photo of a plug covered in dry carbon and say ... Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. If the insulation resistance drops to 0 ohms, the firing end is fouled by either wet or dry carbon.

                        Link
                        http://www.ngksparkplugs.com/tech_su...qs/faqread.asp

                        Rob
                        KEEP THE RUBBER SIDE DOWN

                        1978 XS1100E Modified
                        1978 XS500E
                        1979 XS1100F Restored
                        1980 XS1100 SG
                        1981 Suzuki GS1100
                        1983 Suzuki GS750S Katana
                        1983 Honda CB900 Custom

                        Comment


                        • #13
                          Originally posted by SFerinTEXAS View Post
                          Put clean plugs in 1 and 4, switch plug wires and see if it switches problem to no 1. May not be a fuel problem
                          I did this and 4 still reads the same. I am hoping it was the sync tube. Carbon, my high compression? We will see if the monsoon ever lets up. I need accell coils. 6 ohms with a resitor? I forgot?
                          "We are often so caught up in our destination that we forget to appreciate the journey." "

                          Comment


                          • #14
                            Would the sunk synch tube cause a rich condition of the plug? I say no. That tube should have nothing to do with richness. Maybe a sinking float, a leaking fuel valve seat, the need to vacuum synch the carbs, if it is a problem at low rpms then maybe an adjustment of the pilot screw, or problems with the exhaust ststem.
                            Skids (Sid Hansen)

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

                            Comment


                            • #15
                              I used a set of the K@L gages ( The cost a bunch)and used a vacuum pump to check calibration. Picked up that trick from this site. The mixture was set using Brady's from Merriam Cycles way of lean best idle setting. Turn them in till RPM drops, back it out slowly until the engine sounds like it's the smoothest. Then turn it in a little until there is no difference. Seems to work great. Wished I had an EGA machine to check hydrocarbons and co% of each individual cylinder.

                              Still frigging pouring out
                              "We are often so caught up in our destination that we forget to appreciate the journey." "

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