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1977 gs750B jets

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    #1

    1977 gs750B jets

    Ok. So after making my eyes bleed searching through this site, google, BassCliff's site, and looking through that chart that i found on here with all the carb specs, I have come to start my first thread.

    As the title says, I have a 1977 gs750B. The main jet is #107.5 and the pilot is #17.5. Both have the Mikuni small box inside another box symbol stamped on them. Everythig that i have read has pointed to these not beeing stock jets. Anyways, I have torn down the carbs to clean them in Gunk(wich i have already done) and i have already installed the Cycleorings kit. Have a few questions:

    1. What do i need to do about the jets? Use them without any problems? different air filter? different tuning?

    2. What does the pilot need t be set at? the box in that table i saw somewhere is blank in that box? I found that the mixture screw is supposed to start at 2 turns out.

    I have the gaskets from Z1 ready to go back together.

    Thanks in advance for the input.
    Tags: None
    #2
    Hi Mr. HighCountryGS,

    From the "Early GS750" manual on my little website:



    Is there an aftermarket exhaust on your bike? Are you running pod filters? It seems the jets are a little larger than stock. But there's not enough information to determine what a previous owner may have done, or why.

    For your carbs there are separate fuel and air screws. Generally you'll start with the fuel screw about 7/8 out and the air screw roughly double that. Adjust as necessary. (But I'm no VM carb expert.)

    Now let me dump a TON if information on you and share some GS lovin'.

    I just stopped by to welcome you to the forum in my own, special way.

    If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

    Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Rebuild Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...



    Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

    Thanks for joining us. Keep us informed.

    Thank you for your indulgence,

    BassCliff
    Last edited by Guest; 03-14-2011, 06:21 PM.

    Comment

      #3
      The exhaust is stock for now. I was think about running pods because the stock airbox isn't in the greatest shape. I have seen some sources that say the stock main is #100 and some say #105. Pilots all seem to say #15 i think.

      And by 7/8 out you mean?

      Thanks

      Comment

        #4
        Originally posted by HighCountryGS View Post
        The exhaust is stock for now. I was think about running pods because the stock airbox isn't in the greatest shape. I have seen some sources that say the stock main is #100 and some say #105. Pilots all seem to say #15 i think.

        And by 7/8 out you mean?

        Thanks
        Unless you are running a good flowing aftermarket exhaust keep the stock airbox. You are only asking for headaches. 7/8 out means 7/8 of a full turn out.
        David
        1998 Suzuki Bandit
        1978 GS750 gone but not forgotten
        1978 GS1000 - gone
        1981 GS850 - gone

        Comment

          #5
          Cliff, In the service manual on your website..page 78, under the subsection adjusting the carburators, it states that air screws are out 1 1/4 from bottom..then it goes on to explain how to use the guages to balance the cabs. The thing that seems to eludes us is the DOCUMENTED position for the pilot screws..that what i want to know also.. does anyone have anything in printed literature to conclusively shed a light of factuallity on this???? I mean somehweres in a paralell universe Suzuki had to have published the baselines.
          Last edited by chuck hahn; 03-14-2011, 08:45 PM.
          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
            Originally posted by chuck hahn View Post
            Cliff, In the service manual on your website..page 78, under the subsection adjusting the carburators, it states that air screws are out 1 1/4 from bottom..then it goes on to explain how to use the guages to balance the cabs. The thing that seems to eludes us is the DOCUMENTED position for the pilot screws..that what i want to know also.. does anyone have anything in printed literature to conclusively shed a light of factuallity on this???? I mean somehweres in a paralell universe Suzuki had to have published the baselines.
            No published facts, as the fuel screws were sealed at the factory and considered non adjustable

            The 3/4-7/8 comes from the accumulated knowledge of those that messed with their carbs before you
            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

              #7
              Originally posted by Big T View Post
              No published facts, as the fuel screws were sealed at the factory and considered non adjustable

              The 3/4-7/8 comes from the accumulated knowledge of those that messed with their carbs before you
              7/8 of a turn out. Ok. makes sense. So does anyone have a guess as to what to do with the pilot?
              Last edited by Guest; 03-14-2011, 10:21 PM. Reason: double post

              Comment

                #8
                HIGH COUNTRY..we ARE talking about the pilot jet( the one on the bottom of the carbs). 3/4 to 7/8 out....The other references of 1 out that Basscliff posted and the 1 1/2 out that i had fopund in his online service manual are in reference to the AIR screrw ( the one on the sdies of the carburators ).
                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

                  #9
                  Originally posted by chuck hahn View Post
                  HIGH COUNTRY..we ARE talking about the pilot jet( the one on the bottom of the carbs). 3/4 to 7/8 out....The other references of 1 out that Basscliff posted and the 1 1/2 out that i had fopund in his online service manual are in reference to the AIR screrw ( the one on the sdies of the carburators ).
                  Basscliff's post says 7/8 out on the fuel mixture screw and roughly double that on the air screw. Pilot jet is inside the bowl right next to the main correct?
                  Last edited by Guest; 03-14-2011, 10:22 PM. Reason: added content

                  Comment

                    #10
                    Originally posted by HighCountryGS View Post
                    ok so 7/8 on the pilot, 1-1 1/2 on the air scew, and what for the fuel screw? Since BassCliff said i have a seperate air and fuel screw.

                    EDIT: Basscliff's post says 7/8 out on the fuel mixture screw and roughly double that on the air screw. Pilot jet is inside the bowl right next to the main correct?
                    That's right. Pilot jet is the #17.5 you posted earlier.
                    1979 GS750E

                    Comment

                      #11
                      You guys are confusing the man..Heres the terms you need to know::

                      PILOT JET..THE JET INSIDE THE CARB IN THE LITTLE HOLE NEXT TO THE MAIN JET.YOU PUT THAT IN AND GENTLY THIGHTEN IT AND LEAVE IT ALONE

                      PILOT SCREW..THE SCREW AT THE BACK OF THE CARB BUT NOT INSIDE THE CARBS..AT THE BACK OF THE BOWLS IN THE HOLE.

                      AIR SCREW..THE SCREW ON THE SIDES OF THE CARB BODIES.

                      Now heres what you do..Set the PILOT SCREWS at 3/4 to 7/8 out from bottom..then set the AIR SCREWS at 1 1/2 out as is stated in the PDF service manual....Be sure the intake boot orings are replaced..the intake boots themselves are good and not cracked..valves are properly adjusted. vaccuum sync the carbs and do adjustments as neeeded. Your previous post ..to me..indicated that you are confusing the PILOT JET with the PILOT SCREWS ,,, They are two totally different things..
                      Last edited by chuck hahn; 03-15-2011, 03:54 PM.
                      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
                        Thank you chuck hahn!

                        Yes, screws get adjusted. All jets get snugged into their respective receptacles.

                        Fuel screws and air screws are set at a starting point and adjusted from there. I don't think I've ever seen any true factory recommendations because every engine/carb arrangement is a little different, even on the same model, due to tolerances and variables.


                        Thank you for your indulgence,

                        BassCliff

                        Comment

                          #13
                          Agreed Cliff. These are just as "starting points" as you pointed out. I thought i should have clarified the terms for the man..He seemed to me a bit confused between the pilot jet and the pilot screw. Wasnt meaning to step on anyone elses efforts..I really try to keep it at the K.I.S.S. level ( Keep It Simple Stupid)!!!
                          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

                            #14
                            Originally posted by chuck hahn View Post
                            Wasnt meaning to step on anyone elses efforts..I really try to keep it at the K.I.S.S. level ( Keep It Simple Stupid)!!!
                            I'm glad you took the time to clarify the terminology. Thank you!



                            Thank you for your indulgence,

                            BassCliff

                            Comment

                              #15
                              Originally posted by chuck hahn View Post
                              You guys are confusing the man..Heres the terms you need to know::

                              PILOT JET..THE JET INSIDE THE CARB IN THE LITTLE HOLE NEXT TO THE MAIN JET.YOU PUT THAT IN AND GENTLY THIGHTEN IT AND LEAVE IT ALONE

                              PILOT SCREW..THE SCREW AT THE BACK OF THE CARB BUT NOT INSIDE THE CARBS..AT THE BACK OF THE BOWLS IN THE HOLE.

                              AIR SCREW..THE SCREW ON THE SIDES OF THE CARB BODIES.

                              Now heres what you do..Set the PILOT SCREWS at 3/4 to 7/8 out from bottom..then set the AIR SCREWS at 1 1/2 out as is stated in the PDF service manual....Be sure the intake boot orings are replaced..the intake boots themselves are good and not cracked..valves are properly adjusted. vaccuum sync the carbs and do adjustments as neeeded. Your previous post ..to me..indicated that you are confusing the PILOT JET with the PILOT SCREWS ,,, They are two totally different things..
                              Great reply! THANK YOU! i had it right in my head and i guess it came out wrong. Everyone seems to have there own term for these things.

                              Anyways...Do you think i just need to leave the jets that are in there alone? since they are not stock it seems? If i am correct they are only one size up 107.5 and 17.5?
                              Last edited by Guest; 03-15-2011, 09:36 PM. Reason: abc

                              Comment

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