GS400x Petcock Vacuum Hose and Carb Hoses

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  • Kansas Kid
    • Jan 2026
    #1

    GS400x Petcock Vacuum Hose and Carb Hoses

    Hi all,

    I'm new to Suzuki motorcycles and just about have my GS400X running. I'm stuck on where all of these hoses for the carbs and petcock vacuum hose connect. My carbs do not quite match the image in the GSX400 manual on BikeCliff's website or the carb diagram from the GS400-450 77-87 manuals.

    My carbs have two hoses running from the inside middle of each carb that appear to be item 29 in the 400-450 diagram.

    My carbs are missing the two hoses that run from the bottoms of the float bowls, labeled 26 in the 400-450 attached image.
    Mine do have brass nipples that seem to be where these should attach. The other place my carbs differ from the

    I also can't seem to find where the vacuum hose attaches to the carbs. My carbs do have the attachment mentioned for hose #38 in the 400-450 manual or for the #14 hose in the 400X diagram.

    Any help on deciphering what these variety of hoses are and where they connect would be appreciated.

    Thanks for any insights!
    Attached Files
    Tags: carbs, gs400x, gsx400, vacuum
    • Kansas Kid
      #2
      Here is an image of the gsx400 carb diagram.
      Attached Files

        Comment

        • Steve
          GS Whisperer
          • Jun 2005
          • 35924
          • southwest oHIo
          #3
          Can't read any of the numbers on those small pictures, but the vacuum line that should connect to the petcock comes from the front of carb #2. That is the one under your throttle hand. The "front" side is the engine side. The hose that is closer to the back of that carb, but still on the left side, is a VENT hose. If you have a similar hose on the right side of carb #1, that is also a VENT hose. Those vent hoses get draped over the airbox, where you will likely find a small bracket that will neatly hold both hoses in relatively calm air.

          The fuel line should be rather obvious, going to the T in the middle of the two carbs.

          .
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            Comment

            • Guest
              #4
              Probably, you have a 1977 or '78 GS400X. This is a very different thing from a GSX400 which has a different engine and carbs and was not sold in the US. GSX engines have four valves per cylinder that screw adjust and GS engines have two per cylinder and shim adjustment.

              The carbs you have will have the vacuum line to the fuel tap attaching to the left carb just in front of the choke lever. The remaining vent nipples have hoses going down toward the road at the back of the engine or maybe though some sort of holder on the underside of the air box?.?? it's been a while since I owned one, but as long as they vent out, back and down I don't think it's critical.

              Congrats on [almost] getting an old 400 running; not too many still out there, and I have a certain nostalgia for them.

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