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1980 GS850G with 4 into 1 V&H and K&N filter - what main jets?

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    1980 GS850G with 4 into 1 V&H and K&N filter - what main jets?

    Hey guys, my 82 GS850G has a Vance and Heins 4 into 1 pipe and a K&N Air filter. And it's breaking up badly after about 1/2 throttle. I opened the choke during the break up and it got worse and fell on it's face so I'm pretty sure the main jets are too small.

    I have not opened up the carbs yet but was wondering if any of you that have an 850 and slapped on a V&H pipe and an air filter.. what Jet's did you end up using? (Figured I'd save some time trying new ones)

    Stock is as follows:
    GS850 (80) the specs are for the CV's

    idle.................... 1050 +/- 100 r/min
    carb................... mik BS32SS
    id no................... 45120
    bore size ............ 32 (1.26)
    float height ......... 22.4 +/- 1.0 (0.88 +/- 0.04)
    fuel level ............ 5.0 +/- 0.5 (0.20" +/-0.02")
    VALVE SEAT........ 2.0
    STARTER JET....... 32.5
    PILOT SCREW ..... 3.5
    PILOT AIR JET ..... #200
    pilot jet............... #42.5
    jet needle........... 5D57-3 (the -3 3rd notch)
    needle jet .......... X - 6
    pilot outlet........... 0.7
    BY PASS............. 1.0, 0.8, 0.8
    MAIN AIR JET...... 1.7
    main jet............. #115

    #2
    Half throttle is the needle, and the main jet had little effect
    Most people go to a jet kit, like Dynojet to get a better needle
    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


      #3
      Easiest solution would be to go back to a stock filter and you can use the stock jetting.
      2@ \'78 GS1000

      Comment


        #4
        Is your "K&N filter" a single filter in the stock airbox or is it four individual pods?

        What baffle is in the V&H pipe?

        Both of those will have a BIG impact on what jets to use, but a DynoJet kit will likely cure either situation.

        .
        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


          #5
          Originally posted by Steve View Post
          Is your "K&N filter" a single filter in the stock airbox or is it four individual pods?

          What baffle is in the V&H pipe?

          Both of those will have a BIG impact on what jets to use, but a DynoJet kit will likely cure either situation.

          .

          Single filter in the orig sealed air box, and full baffle, The bike is not loud.

          Thanks in advance.

          3.jpg

          Comment


            #6
            There is a decent chance you may not have to re-jet.

            The airbox is more of the restriction in the intake side than the filter itself, so nothing changes there.

            With a quiet baffle, flow might not be much more than stock, so not much will change there.

            At worst, you might have to go up one size on the main from a 115 to 117.5 and maybe shim the needle a bit.

            I have a K&N insert in my stock airbox, along with a quiet 4-into-1 pipe. I am running stock jetting in the carbs. I think I still need to turn my pilot screws in from when I rebuilt them. They might still be at 3 turn out, they likely need to go in half a turn or so.

            .
            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


              #7
              My sons red 1980 GS850 with a Vance and Hines and K&N filter I only changed main jet to 120 and 2 1/4 Turns out fuel screws. Carb needle jet standard position middle NO3. Have you the rubber intake boot/snorkel attached to the rear of the air filter box? I found when mine was not attached I had similar problems that you are experiencing. Regards.
              GED

              1980 GS850G (BLACK)
              http://www.thegsresources.com/_forum...d.php?t=185562
              1980 GS850G (RED) http://www.thegsresources.com/_forum...d.php?t=219169
              1980 GS850G (SILVER) (Coming soon)

              There are old riders and there are bold riders but there are no old bold riders!!!!!!


              Comment


                #8
                Originally posted by Steve View Post
                There is a decent chance you may not have to re-jet.

                The airbox is more of the restriction in the intake side than the filter itself, so nothing changes there.

                With a quiet baffle, flow might not be much more than stock, so not much will change there.

                At worst, you might have to go up one size on the main from a 115 to 117.5 and maybe shim the needle a bit.

                I have a K&N insert in my stock airbox, along with a quiet 4-into-1 pipe. I am running stock jetting in the carbs. I think I still need to turn my pilot screws in from when I rebuilt them. They might still be at 3 turn out, they likely need to go in half a turn or so.

                .

                Excellent info thanks!

                Comment


                  #9
                  Originally posted by ged View Post
                  My sons red 1980 GS850 with a Vance and Hines and K&N filter I only changed main jet to 120 and 2 1/4 Turns out fuel screws. Carb needle jet standard position middle NO3. Have you the rubber intake boot/snorkel attached to the rear of the air filter box? I found when mine was not attached I had similar problems that you are experiencing. Regards.

                  I will double check this! Thanks!

                  Comment


                    #10
                    I used that setup on a 1000G. I liked it. Better than pods.

                    You don’t need to go up much. I think I ran 122.5 (stock 117), pushed the needle up a bit using washers and ran the air screws at about 3 turns out. I am at sea level.
                    1980 GS1000G - Sold
                    1978 GS1000E - Finished!
                    1980 GS550E - Fixed & given to a friend
                    1983 GS750ES Special - Sold
                    2009 KLR 650 - Sold - gone to TX!
                    1982 GS1100G - Rebuilt and finished. - Sold
                    2009 TE610 - Dual Sporting around dreaming of Dakar.....

                    www.parasiticsanalytics.com

                    TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

                    Comment


                      #11
                      I had that snorkel on the airbox problem and it indeed caused problems.

                      Comment

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