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  • Another Octopus Bypass Question

    Bike is a stock 80 Special.

    Looking at this spaghetti I am tempted to bypass it and just run gas line straight from the tank to the carbs, understanding that its on me to turn off the gas when I get off the bike.

    It seems the only real issue is to somehow block the vacuum holes/ports coming off the tank petcock. I see JB weld and tapping for a screw as two solutions listed here. Other thoughts/methods?

    Could I put hose on both holes in each petcock (4 hoses, 2 each side) and "T" them together or does that funk up the petcock or vacuum somehow? I would like the option to put it back original if I want to do that at some point in the future without digging JB or similar out of the petcock.

    Also, what do I do with the vacuum line off #2 boot when I remove the Octy? Block/plug like the others?

    Awesome site - learning lots here. Thanks!
    80 SG

  • #2
    You can block the FRONT port on each petcock and just use the rear port. Run a fuel line from the right side to the left pair of carbs, and left side to right pair of carbs. You can then remove the octy from the carbs and get rid of all the fuel lines. Use a bit of hose or a vacuum cap from the parts store to block off the port of #2 carb.
    You MUST turn the fuel off when you park the bike, and especially if you park it on the side stand! The center stand keeps the carbs level, so they are less likely to leak. you can use a short fuel line with a screw in it to block the front ports on the petcocks.
    Ray Matteis
    KE6NHG
    XS1100 E '78 (winter project)
    XS1100 SF Bob Jones worked on it!

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    • #3
      Originally posted by DiverRay View Post
      you can use a short fuel line with a screw in it to block the front ports on the petcocks.
      Ha! I use short pieces of thick walled fuel line with bolts in the ends for the manifold nipples instead of the rubber caps.
      Skids (Sid Hansen)

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

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      • #4
        Hey TX,

        The Specials petcocks are just gravity feed, both nipples are fuel supply, the front one is for the PRIME function to bypass the Octy for refilling the bowls. With just the petocks, RUN will work just like Prime, so that's why you don't need the front nipple. SO as has been said, you can put a hose/screw over it, or you can T/Y it together with the other line on the same petcock, OR you can run a long piece of fuel hose across from L to R petcock connecting the two front nipples that way. Your choice.

        IF the carbs and float needles are working properly, then occasionally forgetting to turn off the fuel won't lead to leakage, but IF they do fail, the fuel likes to flow forward into the intake, past an open valve, down into the cylinder past the rings into the oil, and then with contaminated oil, you can burn up the crank/cam bearings!

        T.C.
        T. C. Gresham
        81SH "Godzilla" . . .1179cc super-rat.
        79SF "The Teacher" . . .basket case!
        History shows again and again,
        How nature points out the folly of men!

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        • #5
          Thanks to everyone. Sounds like easy plumbing.

          Another question - where does the vacuum line from the ignition vac advance (lower left side of bike) connect to? I have a length of hose attached to the vac advance but not connected anywhere else. I assume it came loose from somewhere. Can't find a pic of it in my manual. It looks like there was a vac line connected to #2 boot, and one to the octy, not sure if it should go there.

          Thanks!

          Very close to cranking...first time since 2013 (per PO).
          80 SG

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          • #6
            The ignition vac advance hose connects to the #2 Carburetor port NOT the manifold port.
            79 F full cruiser, stainless brake lines, spade fuses, Accel coils, modded air box w/larger velocity stacks, 750 FD.
            79 SF parts bike.

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            • #7
              Originally posted by red bandit View Post
              The ignition vac advance hose connects to the #2 Carburetor port NOT the manifold port.
              Awesome. Thanks!
              80 SG

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