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Need modification advise..VM 29s

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    Need modification advise..VM 29s

    So I got around to firing up the mewly aquired S I went to Kentucky a few months ago to get. I primed the carbs and she fired right up..then died after a few minutes after I put the petcock in the ON position. Reprimed and fired up..repeat scenario a few times. Pulled the tank and there wasnt any vaccuum tube from carbs to petcock. I looked where the port is 'SUPPOSED" to be and there isnt a nipple. In fact the carb body is molded with the usual spot cast closed. I need to mod these so i can hook up a vaccuum to effect proper operation of the petcock. I was thinking about carefully drilling thru the body to open up the spot that would normally have the vaccuum nipple. I can scavenge a nipple off a set of 26s to put in. Question is am I on track with my thinking here? What can I do to get the situation straightened around?
    MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
    1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

    NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


    I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

    #2
    Chuck,

    Use the sync port hole on the head - get a threaded nipple and permanently attach it to the head, then run a vacuum line to your petcock. Simple and effective mod.
    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


      #3
      Me and Dale had talked on the phone earlier and discussed that option. He didnt know though if while rapping up the engine it would cause the diapram any problems. The regular port applies a pulse and its very low suction as well. Thats why i was wondering about opening up the regular spot.
      MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
      1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

      NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


      I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

      Comment


        #4
        The vacuum port on the carb and the sync port are going to see the same amount of vacuum at virtually the same time. There should be NO difference.

        .
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        Comment


          #5
          ok then..anyone got a spare syncing nipple laying around they would like to donate to the cause?
          MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
          1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

          NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


          I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

          Comment


            #6
            You can modify your petcock to make it a manual petcock.
            http://img.photobucket.com/albums/v5...tatesMap-1.jpg

            Life is too short to ride an L.

            Comment


              #7
              PM me the details....PLEASE!!!
              MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
              1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

              NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


              I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

              Comment


                #8
                Originally posted by tkent02 View Post
                You can modify your petcock to make it a manual petcock.
                This VM29 modification has worked fine for me; Turn your petcock to Prime when running and Off when not running
                Steve

                1979 GS1000E (45 Yrs), 1981 GPz550 (11 Yrs)

                Comment


                  #9
                  Supertrap..yeah that works too, but knowing me i will forget to turn it off and if the carbs leak a bit i dont want to run a risk of filling the crankcase with gas..
                  MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
                  1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

                  NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


                  I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

                  Comment


                    #10
                    Chuck

                    Just my two cents but I believe everyone running VM29's have merely capped the vacuum port of the GS1000 petcock and used

                    Prime position for On
                    On position for Off (since we have disconnected & discarded the vacuum tube).

                    So you are back to a gravity feed setup and I have never had any problems in 25+. Personally I would not modify the VM29's to accept a vacuum port because that will diminish the value of the best bolt on Carb Mikuni ever made
                    Last edited by srsupertrap; 03-05-2011, 06:50 PM.
                    Steve

                    1979 GS1000E (45 Yrs), 1981 GPz550 (11 Yrs)

                    Comment


                      #11
                      I have the original set of 26s that were taken off many years ago but they are all crapped up inside.. I dont really want to get into doing another set of carbs right now, so i guess i had better get used to the idea of turning it to the on position everytime i get off the bike. If I put the 26s back on I will most likely sell the 29s. They are spotless and are running very well on the bike right now.
                      MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
                      1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

                      NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


                      I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

                      Comment


                        #12
                        For Vm29s you need to run the bike with the petcock on "Prime". I had the same problem when I got mine. Just remember to turn off the petcock when the bike is not running. My vacuum hose from the petcock is not connected to anything.

                        Comment

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