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The octy monstrosity

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  • The octy monstrosity

    Since nobody talks about this thing, I figured I would break the ice.

    So in my intro post, I described how this thing was leaking. When I say leaking, I don't mean seepage or drip. I mean, it sprays out at a rate that is probably close to its full flow. It leaks right from the edge of it. So I took it apart to inspect.

    Honestly, all the rubber looks pretty good. I'm not confident a rebuild would resolve the problems, but I'll be interested in the feedback.

    There are three main questions I was wondering about:
    1. In the cheese layer of the octy sandwich (the thick plastic part), does it matter where that little groove that runs to the outside edge is located?
    2. What is that little black disc in the picture? I can find no reference to it anywhere, except the old link listed below. The OP mentions this thing, but nobody knows what he's talking about. When that disc is installed in the vacuum nipple hole, it acts like a check valve - I can suck very little air (probably just enough to move the diaphragm) but cannot blow any. When removed, I can suck and blow enough to hear the diaphragm move back and forth. Which is correct?
    3. Does anyone know the correct lengths of all of the octy's arms, or each fuel line segment? I think someone replaced mine at some point in history and the lengths are off. It's a bear to install and the lines get all kinked in order to make the turns to each connector or the petcocks.
    http://www.xs11.com/forum/archive/in...p?t-20721.html


    Click image for larger version

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    Last edited by TheNannerpus; 10-03-2021, 09:44 AM.
    Started riding in Sept. 2019

    1983 Honda CB650 Nighthawk (sold)
    2009 Suzuki GS500 (sold)

    2019 Suzuki SV650
    1993 Honda Nighthawk 750
    1980 Yamaha XS1100 Special (project)

  • #2
    There is a reason so many of us remove the octy. The reason for it in the first place was to shut off the gas flow when the engine was not running. On the Standard models, that function is in the petcocks, and they are large because of it. On the larger tank, you don't notice it. With the Specials, the tank is smaller, and there is less room for a petcock with a vacuum valve built in. I blocked the front nipple on each petcock and just use the rear to feed the carbs. easier to run the lines, and no leaks. Do a search on it in the "modification" section.
    I have also rebuilt and used the octy in one of my bikes. georgefix on ebay has the correct kit. You need to verify that all the rubber bits are installed correctly! Also need to verify that the "O" ring fits the shutoff correctly.
    Looking at the picture, I think your octy had someone work on it before, and parts may not be installed correctly.
    Ray Matteis
    KE6NHG
    XS1100 E '78 (winter project)
    XS1100 SF Bob Jones worked on it!

    Comment


    • #3
      Check valve in vacuum port, yes keep it. The rest, cheese layer...... Two diaphragms on a valve stem. Seat side seals the fuel in (you probably have a breach in this layer. The other side has the atmosphere pressure path between the two and the intake vacuum on the other so when the bike it running the diaphragm moves toward the lower pressure to open the valve. Open it up. K&L has a kit for these. P/N 18-5100 (you will need to replace the o-ring on the valve stem to get it to seal properly.

      ----Bax
      80 SG, --- Slightly modified with EFI.....

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      • #4
        https://xs11.club/forum/idle-talk-fo...ock#post859030

        See #6 for o-ring details

        ---Bax
        80 SG, --- Slightly modified with EFI.....

        Comment


        • #5
          I suppose there might be some satisfaction in rebuilding it, but I think most people just delete it. one less thing to worry about, as long as you shut your petcocks off.
          2010 Kawasaki Z1000
          1979 SF: Millennium Falcon, until this Saturday

          Comment


          • #6
            Originally posted by tommystinson View Post
            I suppose there might be some satisfaction in rebuilding it, but I think most people just delete it. one less thing to worry about, as long as you shut your petcocks off.
            I would argue that most people do not get rid of it. It is both a fuel pump and a safety feature so why would you just get rid of it because you think it is complicated? If in good shape, and why wouldn't it be with rebuild kits available, it stops the flow of gas when the bike is shut down. Like I said in a previous post ... just get in the habit of turning the petcocks off when you park the bike. Octi or no Octi... just a good habit to get into.
            2 - 80 LGs bought one new
            81 LH
            02 FXSTB Nighttrain
            Jim

            Comment


            • #7
              It is both a fuel pump and a safety feature so why would you just get rid of it because you think it is complicated?
              It is NOT a fuel pump. It is an automatic, vacuum operated shutoff valve for the fuel. Because the proper fuel lines are very hard to find, it is a PITA to get working correctly. As most fuel line is now 1/4", and not metric, it will not fit quite as tight as it should. It also has a larger outside diameter, and that makes it harder to get all the lines installed without kinking.
              Ray Matteis
              KE6NHG
              XS1100 E '78 (winter project)
              XS1100 SF Bob Jones worked on it!

              Comment


              • #8
                Originally posted by DiverRay View Post
                It is NOT a fuel pump. It is an automatic, vacuum operated shutoff valve for the fuel. Because the proper fuel lines are very hard to find, it is a PITA to get working correctly. As most fuel line is now 1/4", and not metric, it will not fit quite as tight as it should. It also has a larger outside diameter, and that makes it harder to get all the lines installed without kinking.
                thanks for correcting my error Ray. I see what you are saying about the fuel lines, but honestly I have never had a problem with fuel lines kinking. I understand why many get rid of the Octy but I have really never had a problem with it and like the idea that when operating correctly it shuts the fuel flow when the engine is stopped.
                2 - 80 LGs bought one new
                81 LH
                02 FXSTB Nighttrain
                Jim

                Comment


                • #9
                  Here is comprehensive instruction for Yamaha vacuum fuel valve repair.
                  https://xjbikes.com/forums/threads/r...-w-pics.25058/
                  Marty (in Mississippi)
                  XS1100SG
                  XS650SK

                  Comment


                  • #10
                    I am with DiverRay,,,I tossed the octi years back and just turn off the petcocks when done riding. If the carb float needles are good you dont even have to turn off the petcocks but for safety the off position is good especially for long term sitting. The octi in theory works great, but age, old fuel lines, a pia to connect, a pia to synch with all the extra lines,,,,,it felt good to throw it out after all the hassle,,,,good luck,,,MIke in Sun Diego

                    Comment


                    • #11
                      I've decided to remove the octy. Tough call, since my screen name here seems like it's a family member somehow.

                      I have already ordered the new lines and y connectors (I'm not capping the PRI valve, I'll just merge the two lines) to bypass the octy. I'll put the octy in the XS spare parts bin. For now I'll shut them off manually. I may add a different vacuum activated valve down the road. In winter, I'll disconnect the fuel lines from the carbs and dangle those over the sides. If it leaks, it'll leak on the garage floor. Or maybe I'll plug that end...idk yet.

                      I get that the octy is a safety feature. I gotta think there's a better way to accomplish that same task now. Ideally, a single valve, vacuum-activated petcock to replace each current dual valve setup.
                      Started riding in Sept. 2019

                      1983 Honda CB650 Nighthawk (sold)
                      2009 Suzuki GS500 (sold)

                      2019 Suzuki SV650
                      1993 Honda Nighthawk 750
                      1980 Yamaha XS1100 Special (project)

                      Comment


                      • #12
                        Howdy Nannerpus,,,,,there also is another sure way to make sure the gas will not flow to the carbs, is to install a cheapo plastic shutoff, they are available at any lawnmower shop, or home depot, plumbing section. I have used them on various restored xs's. Just run a line from the petcock to the shutoff with enough line to stick out for turning purposes. I remember someone way back just used one plastic shutoff with both carbs connected to it to make it easier to turn off the fuel flow. I think it loses the reserve capability but much easier to remember to turn just one shutoff instead of two, also these bikes will run off just one petcock, just block off the lines from the other petcock. Anyway, good luck,,,,Mike, Sun Diego

                        Comment


                        • #13
                          Simple octy, only 3 hoses, use with just one petcock, a bit pricey...

                          Beware of ebay cheap China junk fuel taps because that's just what they are, DAMHIK

                          http://www.pingelonline.com/pc_produ...C89EC32D85EB11
                          2H7 (79)
                          3H3

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