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Popping and mist from vacuum nipple at carb #2

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    #1

    Popping and mist from vacuum nipple at carb #2

    I just finished dipping/cleaning my carbs and put them back on the bike. Prior to install I bench synched the vacuum and turned the air screws exactly two turns out(up). When I started up the bike there would be this popping (more like a "fip" sound) and a mist of presumably gas would spray out of the vacuum nipple at carb #2 (yes while the vacuum hose is attached so the pressure must be high).

    I need to make fuel/air adjustments and perform a vacuum sync obviously but does anyone have an idea of what is physically happening so I know what to quickly adjust first when I start? Is it not enough vacuum?

    Oh and the valves have already been adjusted and my airbox is sealed.
    Last edited by Guest; 11-07-2011, 03:04 PM.
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    #2
    Uh oh...

    You MAY be sucking gas through the vacuum line. A pop? Like a backfire? Or more like someone popping their cheek with a finger?

    Do you have a new line secured to the nipple with a spring clip?
    '83 GS650G
    '83 GS550es (didn't like the colours in the 80's, but they've grown on me)

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      #3
      It's simply a "fip" sound of the gas mist escaping from the vacuum nipple. It takes a higher pressure to push through the nipple (with the hose attached)

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        #4
        Does it also mist when you disconnect the vacuum line?
        '83 GS650G
        '83 GS550es (didn't like the colours in the 80's, but they've grown on me)

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          #5
          Ok. I figured it out. Sorry, I freaked out a little when I saw gas mist spraying OUTSIDE the bike.

          I'll write out my procedure in case any newbee (like me) could use it. When I regained composure I turned the air screw one turn left (out) thinking it was way rich then I realized my idle adjuster wasn't engaged at all so I turned it right (in) maybe 5 or 6 turns to engage it so I can actually use it to adjust the idle. I happened to have a carburetor synchronizer attached and noticed carbs 1, 2, and 4 were the same and 3 was way low. Considering all the other carbs should be adjusted relative to #3 I turned up my idle using the big idle hand screw in until I would reach 2k rpm then turn the vacuum screw left (out) until I would reach 900 rpm. Kept turning idle thumb screw in and vacuum screw out until all four carbs matched on my synchronizer. Once they matched I turned the idle screw right (in) until I reached 1050 rpm (correct idle rpm per manual). No popping.
          Last edited by Guest; 11-07-2011, 05:04 PM.

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            #6
            Yeah. I plugged the vacuum line and used a gravity fed auxiliary fuel tank.

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