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Wrong Carb, which Jets?

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    #1

    Wrong Carb, which Jets?

    Hey Folks,
    The previous owner of my 1985 GS550LF must have replaced the carb at some point because the main and idle jets do not match what the Haynes manual says they should be. I know he didn't re-cam it or do any exhaust mods to need richer/leaner jets. The bike is completely stock.

    Anyway, according to my Haynes, the LF and LD models got a lot of different combinations of jets/needles/air valves, etc...

    If I replace JUST the main jets and idle jets to match what I should have in the carb from the factory, will I be good to go, or should I just find a "new" carb setup from someone? Im looking to do this as painless as possible....and as cheap as possible, and I know a new carb isn't going to be cheap

    For what its worth, the carbs are Mikuni BSW30SS

    Thanks Much,
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    #2
    How does it run now? Are the jet sizes way off from what the manual says it should be?

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      #3
      the jets are currently as follows:

      Main: 95 and 105 (should be 90 and 97.5...2 steps lower)
      Idle: 35 (should be 37.5...1 step larger)

      basically it looks like the bike is running leaner than is should at idle and richer than it should at part/full throttle.

      The bike runs OK, but takes forever to warm up and stalls if the choke isn't on till its fully warm. It also blows a lot of smoke (due to incorrect jets) and idle and I stink like bad exhaust after riding.

      Any info...greatly appreciated!
      Thanks,

      Comment

        #4
        Who knows why they would have been changed. Maybe he had a 4 into 1 that he sold and put the stock exhaust back on. Jets (at least mains) are cheap. You could pick up the stock size mains and go from there but dialing in a set of carbs isn't that straight forward. There are so many factors involved. Maybe he was running a little richer because of temperature or elevation. Have you checked the needle height and fuel mixture settings yet and how do they compare to what the manual says?

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          #5
          when I got the bike, the carbs were all gummed up. My guess is the previous owner before him had gummed up carbs too and didn't know how to clean them, so rather than pay someone to clean them and do it right, he went to a scrap yard and grabbed the same carb from a different model bike.

          The jetting my carbs currently have are for the LD model, not the LF model which is where im getting my basis for comparison.

          Im just want to know if Im going to have to replace all the little other odds and ends that are different between the LD and LF models as well as the main/idle jets.

          Comment

            #6
            You could get a rebuild kit for your model bike. The kit should have the correct jets.

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