Making stock petcocks manual

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  • chuck hahn
    Forum LongTimer
    Past Site Supporter
    • May 2009
    • 25918
    • Norman, Oklahoma

    #1

    Making stock petcocks manual

    Does anyone have the tutorial about how to make a stock vacuum petcock a manual ON/OFF type??? Thanks.
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  • Blue Falcon

    #2
    add an on/off valve... $5-$10.. just need the hose, clamps and mount. Total $15

    Gas line coming out of petcock ---> on/off valve inlet ---> on/off valve outlet ---> carbs/fuel rail . vac caps, hole in diaphragm etc.

    not what you lookin for as answer ... but here is a video

    convert vacuum to manual
    Last edited by Guest; 02-23-2017, 11:12 PM.

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    • dorkburger
      Forum LongTimer
      Past Site Supporter
      • Jan 2013
      • 10769
      • Stupid Freehold Boro NJ

      #3
      Tkent wrote up a little piece about it. Sometime last year maybe.
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      • Gorminrider
        Forum Sage
        Past Site Supporter
        • Aug 2012
        • 4803
        • British Columbia, Canada

        #4
        With the existing tap, working properly, simplest way is: remove fuel tap vacuum line and put a plug in it. (to stop air being sucked into intake manifold)

        Turn petcock to "Prime" position = Gas ON
        Other positions =gas OFF ( because thereby,you have disabled the vacuum that pulls the the "fuel flow piston" out against spring pressure. )

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        • TxGSrider
          Forum Sage
          Past Site Supporter
          • Aug 2015
          • 1015
          • Flower Mound, TX

          #5
          This is a good idea that would never work for me... I'm too stupid to remember to switch mine from "Pri" to "On" after I start it and have flooded my crankcase with gas at least 2x because of it. LOL!

          It would be nice to find an electrically operated one... or some float needles that didn't leak.
          1982 GS1100E "Jolene"

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          • Gorminrider
            Forum Sage
            Past Site Supporter
            • Aug 2012
            • 4803
            • British Columbia, Canada

            #6
            Well no tap is going to work well if your float needles aren't working. If you are finding oil in gas when left on Prime, maybe you are running rich when riding too. More so with a full tank. I suppose It can be a can of worms because the carburetor gets tuned to allow for fuel supply problems....

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            • TxGSrider
              Forum Sage
              Past Site Supporter
              • Aug 2015
              • 1015
              • Flower Mound, TX

              #7
              I just think its the nature of those carb float needles... if it wasn't they wouldn't need the vacuum operated petcocks to begin with.
              1982 GS1100E "Jolene"

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              • bwringer
                Forum LongTimer
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                • Oct 2003
                • 17066
                • Indianapolis

                #8
                Originally posted by TxGSrider
                I just think its the nature of those carb float needles... if it wasn't they wouldn't need the vacuum operated petcocks to begin with.
                Yep. They're not designed to nor are they capable of holding back a tank of gas for very long. If the petcock isn't shut off by hand or by vacuum, you WILL get a crankcase full of gas. They'll usually make it through lunch OK, but definitely not overnight.
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                • TxGSrider
                  Forum Sage
                  Past Site Supporter
                  • Aug 2015
                  • 1015
                  • Flower Mound, TX

                  #9
                  Originally posted by bwringer
                  Yep. They're not designed to nor are they capable of holding back a tank of gas for very long. If the petcock isn't shut off by hand or by vacuum, you WILL get a crankcase full of gas. They'll usually make it through lunch OK, but definitely not overnight.
                  What I do think is a little odd though, is that Ive got a couple of atvs that have manual petcocks and they'll set for weeks and not leak a drop. I wrote it off to maybe they do leak just a little and its not noticeable... but since theres 4 carbs on my GS and each one leaks just a little... its way more noticeable.
                  1982 GS1100E "Jolene"

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