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1980 rebuild and stumped

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  • 1980 rebuild and stumped

    80 special starting rehab , carbs are clean and rebuilt, air mixtures drilled out and new sets put in, new battery, plugs, so far.
    will start with choke in full open position , will race up to 4 to 5 k rms then drop down and hunt floating between 1500 and 2000 rpm. if i drop the choke down to the second position it kills the engine. Start it back up on full choke and it races back up to 5000 or better for a bit then comes back down. pick up wires look ok and resistance at the cdi plug looks good. Where would you go from here? Thanks for any advice

  • #2
    Did you check the vacuum caps? They can crack and cause all sorts of issues. Are you sure the carbs are clean? I have sworn in the past they were only to find dirt in them. Even though I run fuel filters on the lines, gum and varnish in todays fuels can cause issues.
    1980 XS1100 SG
    Inline fuel filters
    New wires in old coils-outer spark plugs
    160 mph speedometer mod
    Kerker Exhaust
    xschop K & N air filter setup
    Dynojet Recalibration kit
    1999 Kawasaki ZRX1100
    1997 Jeep Cherokee 4.5"lift installed

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    • #3
      Hey, BigalG nice to see another New Englander on the board. Okay first step would be to get the idle down to a workable rpm. When it's running on full richening position try and turn down the idle stop screw (bottom of carb array) until 2k rpm or so and then try to hit half rich position. Do you have the vac advance ported to the carb or is it in the boot? Carb is correct placement.

      -Bax

      80 SG

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      • #4
        What you are referring to "air mixture" is spring loaded screw on engine side, top of carb body? Or fixed air jet pressed into the mouth of the carb?

        ----Bax
        80 SG

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        • #5
          Thanks guys, the carbs are sparkling, i recently finished a 79 special so i know how many times you have to clean them to be sure.... vacume advance is on the carb body, vac caps are solid. Air mixture screws on the 80 are under caps that had to be drilled out, replaced all of those with new orings and screws, no broken tips....

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          • #6
            Did you, by any chance, replace the pilot jets with the parts in the K&L carb kit?

            The pilot jets in those kits are the wrong size, and I had similar symptoms until I figured it out by reading old posts on this forum.
            -Mike
            _________
            '79 XS1100SF 20k miles
            '80 XS1100SG 42k miles
            '81 XS1100H Venturer 35k miles
            '79 XS750SF 15k miles
            '84 Honda V65 Magna ? miles
            '85 Honda V65 Magna ~7k miles
            '84 Honda V65 Magna 48k miles (parts bike)
            '86 Yamaha VMAX 7k miles

            Previous: '68 Motoguzzi 600cc + '79 XS750SF 22k miles

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            • #7
              these were the specs on the carb kit
              Float bowl gasket
              2.0 Float needle and seat
              #110 & #42.5 jets
              Mixture screw, o-ring, washer

              I saw an old post from TC that said some of the 80's carbs did not use the rubber pilot jet caps because they were built different and drew from the maine bowl. When i opened up the carbs for the first time i thought the po forgot to replace them and so i orderd a set ant put them in . ??
              Thanks for the help
              winters comming

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              • #8
                Originally posted by BigalG
                When i opened up the carbs for the first time i thought the po forgot to replace them and so i orderd a set ant put them in . ??
                Thanks for the help
                winters comming
                Bingo! Up to the last post it read like clogged pilot jets. That's exactly what you have. Remove the plugs. Also, you'll have a much easier time with genuine Mikuni jets.
                Marty (in Mississippi)
                XS1100SG
                XS650SK

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                • #9
                  Good work BigalG.
                  Howard

                  ‘01 ZRX 1200, only bike in the garage.

                  2020 Rally Link:
                  http://www.appleattic.net/XS2020/xs2020.html

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                  • #10
                    Yes that was it, runs like a champ, rode it up and down the street , tomorrow carb tune. fork seals are leaking though, how much do i worry about that

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                    • #11
                      Besides the inconvenience of adding fluid eventually and the mess of leaky fork seals, if left alone and it gets worse it can eventually contaminate the brake pads.
                      Howard

                      ‘01 ZRX 1200, only bike in the garage.

                      2020 Rally Link:
                      http://www.appleattic.net/XS2020/xs2020.html

                      Comment


                      • #12
                        Originally posted by BigalG View Post
                        fork seals are leaking though
                        Nine times out of ten it is just dirt lodged in the fork seal, I would try the 35mm film cleaning trick first. I have fixed many seals this way so I know it works most of the time, YMMV. Here is a link to a You Tube video if you are unfamiliar with the process...

                        https://www.youtube.com/watch?v=niYSt1oyzKA

                        2H7 (79)
                        3H3

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                        • #13
                          I’ve cut a piece from a plastic H2O bottle, maybe easier to find than 35mm film... In this digital age, doncha know.
                          Howard

                          ‘01 ZRX 1200, only bike in the garage.

                          2020 Rally Link:
                          http://www.appleattic.net/XS2020/xs2020.html

                          Comment


                          • #14
                            Cut one from a 1/2 gallon milk jug. Make sure your not running any air pressure or more oil will come out than you expect.
                            1979 XS1100 Special
                            1980 XS1100 Std parts bucket
                            1987 ZL1000 Eliminator
                            1976 XS750D Project in waiting

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