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Pro Rebuilt Carbs, New Plugs, New Petcock, New Vacuum line - starving for fuel

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    Pro Rebuilt Carbs, New Plugs, New Petcock, New Vacuum line - starving for fuel

    Hello all:

    I have an 85 GS700e. A bit of background. It was running very strong a few months ago, however, started the annoying problem of dumping fuel into the airbox at an alarming rate. Looking into how to fix, I discovered several problems: 1) the carbs were not stock, and at this point I can't find anyone who can identify them; 2) the Petcock appeared largely useless as the vacuum line wasn't even hooked up to it - no idea how it was running; 3) the plugs were uniformly covered in serious black soot.

    Because I really like the bike and its in good overall shape, and I couldn't do much with carbs I couldn't even identify and were wrong for the bike, I decided to do the following:

    1) replaced the carbs with refurbished Mikuni BS32mm by WiredGeorge. They are from an older GS750. Jetted for air pods.

    2) removed the airbox and installed EMGO air pods

    3) replaced the Petcock with a K&L 18-4358 model, which claims to work on my bike (who knows)

    4) replaced all the spark plugs with new NGK D8EA

    5) replaced intake boot o-rings

    6) replaced vacuum hose for petcock with OEM

    Since that time, the bike is acting like it is absolutely starving for fuel. It starts well although I have to prime the carbs every single time, which may be a sign. It idles very strong and just purrs along beautifully at idle, and will rev strong. But as soon as I get on it to ride, I literally can barely move. It bogs down immediately. I'm lucky to get above 10 MPH and often have to stop and prime the carbs again.

    I trust WiredGeorge's work and reputation; my sense is this is a petcock-to-bowl problem. Any thoughts out there? Should I just do my best to buy an OEM Petcock if I can find one? Thanks for any insight.
    Last edited by Jenkin; 02-15-2021, 03:20 PM.

    #2
    Now you have the right carbs you should jet them for your bike.... put the airbox back on - you won't regret it....
    Get yourself an OEM petcock, it's well known around here K&L bits are cr@p.
    -Mal

    "The only reason for time is so that everything doesn't happen at once." - B. Banzai
    ___________

    78 GS750E

    Comment


      #3
      Thanks Mal - I should mention, the airbox that came with the bike was modified/cut/patched/messed-up significantly to accommodate for what I now know were the wrong carbs. I did ask that my refurb carbs be jetted for air pods when purchasing, I’m confident they have been. Seemed like a simpler solution if jetted properly but I imagine I could find many opinions about that here...

      Thanks for your opinion on my aftermarket Petcock. Others agree with that as well?

      Comment


        #4
        Do the simple stuff first....test your petcock...in “on “ or “re” position no fuel should flow until vacuum is applied to petcock vacuum fitting : suck on it..you should see a good flow. Make sure your gas tank cap vent is not plugged and blocking fuel flow to bowls..leave cap loose and see if fuel flows better.
        1981 gs650L

        "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

        Comment


          #5
          I went through this a few years ago. My wife says
          Did you check the fuel filter?






          Of course I checked the fuel filter...






          I checked it again when she wasn't looking & found it full of snot & nasty.
          Paul


          sigpic




          Originally posted by Grimly
          Watery bints handing out swords is no basis for any system of government.

          Comment


            #6
            Throw those crappy EMGO pod filters in the nearest trash can and buy some decent filters, APE or K&N.
            1978 GS1085.

            Just remember, an opinion without 3.14 is just an onion!

            Comment


              #7
              Thanks all for the input. I acknowledge I have some budget choices of parts (K&L Petcock and EMGO filters) but unless either is a total failure, it doesn’t seem like either would be the sole cause of a total loss and gas starvation under load. As a troubleshooting step, I put on a clear fuel hose to see what was happening with the fuel. When the petcock is on, fuel is going into the hose and the hose fills up. However, there’s also an air bubble at the top of the hose which doesn’t make a lot of sense.

              I wonder if I have a challenge with vacuum forming in the fuel bowls? Perhaps it isn’t venting properly, and the bowls aren’t filling quickly enough to supply fuel. That may also explain the air bubble I’m seeing in the fuel hose? Just thinking out loud -

              Comment


                #8
                Break out the duct tape and tape over half the surface of the pods.
                1978 GS 1000 (since new)
                1979 GS 1000 (The Fridge, superbike replica project)
                1978 GS 1000 (parts)
                1981 GS 850 (anyone want a project?)
                1981 GPZ 550 (backroad screamer)
                1970 450 Mk IIID (THUMP!)
                2007 DRz 400S
                1999 ATK 490ES
                1994 DR 350SES

                Comment


                  #9
                  Break out the duct tape and tape over half the surface of the pods.

                  If it improves, the jetting is wrong
                  1978 GS 1000 (since new)
                  1979 GS 1000 (The Fridge, superbike replica project)
                  1978 GS 1000 (parts)
                  1981 GS 850 (anyone want a project?)
                  1981 GPZ 550 (backroad screamer)
                  1970 450 Mk IIID (THUMP!)
                  2007 DRz 400S
                  1999 ATK 490ES
                  1994 DR 350SES

                  Comment


                    #10
                    Originally posted by Jenkin View Post
                    I wonder if I have a challenge with vacuum forming in the fuel bowls? Perhaps it isn’t venting properly, and the bowls aren’t filling quickly enough to supply fuel. That may also explain the air bubble I’m seeing in the fuel hose? Just thinking out loud -
                    It might not be vacuum, it could be PRESSURE in the bowls.

                    Along that line of thought, what is the status of the carb vents? A surprising number of new owners don't understand where all the hoses go, and frequently get them wrong.

                    .
                    sigpic
                    mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
                    hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
                    #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
                    #2 son: 1980 GS1000G
                    Family Portrait
                    Siblings and Spouses
                    Mom's first ride
                    Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
                    (Click on my username in the upper-left corner for e-mail info.)

                    Comment


                      #11
                      Originally posted by Big T View Post
                      Break out the duct tape and tape over half the surface of the pods.
                      If the bike runs better after doing this you will then know the jetting is off.
                      Ed

                      To measure is to know.

                      Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

                      Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

                      Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

                      KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

                      Comment


                        #12
                        Hey Jenkin, I sent you have a private message.
                        1983 GS1100E, 1983 CB1100F, 1991 GSX1100G, 1996 Kaw. ZL600 Eliminator, 1999 Bandit 1200S, 2005 Bandit 1200S, 2000 Kaw. ZRX 1100

                        Comment


                          #13
                          Steve - thanks for the response. These are just simply vents between bowls 1-2 and 3-4. Ideally one could attach hoses and take them up over the swing arm, but for now they are just open and between the carbs bowls. “Should” be venting fine.

                          Comment


                            #14
                            Thanks - yep, checked the fuel filter, very clean (which I’d expect with a brand new petcock)
                            Originally posted by slayer61 View Post
                            I went through this a few years ago. My wife says







                            Of course I checked the fuel filter...






                            I checked it again when she wasn't looking & found it full of snot & nasty.

                            Comment


                              #15
                              Thanks - yes, tried the above. Petcock is working well and tried venting the gas cap. Replied to an earlier post that I put a clear fuel line on for troubleshooting and fuel is always in the line, so I’m thinking the petcock is doing OK so far. Problem continues even after I prime the carbs for a few seconds to fill them up.

                              Originally posted by tom203 View Post
                              Do the simple stuff first....test your petcock...in “on “ or “re” position no fuel should flow until vacuum is applied to petcock vacuum fitting : suck on it..you should see a good flow. Make sure your gas tank cap vent is not plugged and blocking fuel flow to bowls..leave cap loose and see if fuel flows better.

                              Comment

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