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    fuel air mix?

    i have an 85gs700es that is supposedly bored out to a 750 and i have been having problems with it dying after a long ride on the freeway and it has burned up two sets of spark plugs. someone on here told me it might be running lean causing pre-ignition. if it is bored out to the higher displacement what can i do to get the mix right so that it stops burning up spark plugs and leaving me stranded on the highway?

    #2
    It is simply a matter of re-jetting,try one size larger on the main jet ,or hopefully someone willpost the jet sizes of a 750 version, you could even try bikebandit and look up the jets out of a 750.
    Dink

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      #3
      Are you sure they didn't tell you it had the same bore as a 750? Even 700 carbs and 700 specs wouldn't cause your problem.

      A couple of things you need to check. Valve clearance is where I would start. It's common to find valves that are too tight after time. If you have valves not seating right you can run very hot.

      What intake and exhaust combination are you running? Things like individual filters, header, jet kit. If you have a header and free flowing air filter(s) you need to make sure a jet kit was installed. You can tell real quick by pulling the top off of one carb and carefully lifting one slide out. Be careful with the diaphram on the slide. Then with a pair of needle nose pliers or hemostats remove the clip that's down inside the slide. Pull out the needle and pay attention to how the spacers, spring, and clip are arranged. If the needle has 5 or 6 grooves then a jet kit has been installed. If not you have stock jets that aren't working with intake/exhaust mods.

      Also check the o-rings on the cylinder side of the intake manifolds. They may be hard and not sealing.

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        #4
        test 8)

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          #5
          Perhaps i missed it but what color are the plugs runniung ???

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            #6
            Carb specs for the 83 GS750:
            Main jet: 117.5
            Jet needle: 5D12
            Needle jet: Y-6
            Pilot jet: 37.5
            Those are the differences per the factory manual. Hope it helps.
            BTW, you are running the stock air box?

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              #7
              Originally posted by Gary
              Carb specs for the 83 GS750:
              Main jet: 117.5
              Jet needle: 5D12
              Needle jet: Y-6
              Pilot jet: 37.5
              Those are the differences per the factory manual. Hope it helps.
              BTW, you are running the stock air box?
              Grotton Connecticut??

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                #8
                4 miles away.

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                  #9
                  thanx for your input

                  it actually turned out that there was sediment in the gas tank that was clogging the petcock when the fuel would get low. damn old gas tanks!
                  any ways it was easily fixed by cleaning out the gas tank. i used kreem's fuel tank acid treatment. which by the way, did not impress me. I think there was actually more rust after two days of soaking in their acid treatment than there was when i started. but the sediment did get flushed out and I have no longer experienced this problem!
                  Thanks to all who replied with suggestions!

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