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Aftermarket exhaust and trying to maintain stock jetting

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    Aftermarket exhaust and trying to maintain stock jetting

    Hello everyone. So when I bought my bike it unfortunately did not have the stock exhaust. The PO had bought some aftermarket headers and I'm wondering if with the correct mufflers, can I make it work with the stock jetting. I'm not sure who made the headers but they are a 4-into-2 and have an outlet diameter of 1.985 inches. I'm having a tough time finding mufflers that except this diameter, although I guess I could go with a 2 inch muffler. Or should I just try and find a stock exhaust setup? Thanks.
    -Theo

    #2
    One of the more popular 4-into-2 exhaust sytems was MAC, but I don't know what the diameter of the outlets would be. My suggestion would be to find mufflers that fit, then re-jet if necessary. Don't try to adjust your mufflers to match your stock jets, it's much easier to do it the other way around.

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      #3
      If you are keeping the stock airbox your jetting requirements won't be nearly as difficult as adding pods. I'd go up a couple of sizes on the mains and see if that's enough. If you have pods, get a jet kit regardless of what exhaust you are using.
      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


        #4
        Originally posted by Nessism View Post
        If you are keeping the stock airbox your jetting requirements won't be nearly as difficult as adding pods. I'd go up a couple of sizes on the mains and see if that's enough. If you have pods, get a jet kit regardless of what exhaust you are using.
        No pods for me. I don't want to deal with that headache right now. My stock size is 112.5 and the next size up is 115. So is that what you mean when you say two sizes up...two numbers? Or do you mean two actual sizes putting me at a 117.5? Is cyclerecycle a good place to order them or should I get it from somewhere else. Sorry for all of the questions. Just trying to learn. Thanks.
        -Theo

        Comment


          #5
          Originally posted by Theo View Post
          No pods for me. I don't want to deal with that headache right now. My stock size is 112.5 and the next size up is 115. So is that what you mean when you say two sizes up...two numbers? Or do you mean two actual sizes putting me at a 117.5? Is cyclerecycle a good place to order them or should I get it from somewhere else. Sorry for all of the questions. Just trying to learn. Thanks.
          -Theo
          Yea, I'd try the 117.5's. You might also want to shim the needles too. Do a search on that topic if you don't understand what this means and how to do it for the BS Mikuni's (I'm too lazy to type it all out again).
          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


            #6
            Originally posted by Steve View Post
            One of the more popular 4-into-2 exhaust sytems was MAC, but I don't know what the diameter of the outlets would be.
            .
            Well you're right Steve. I looked up pictures of MAC exhaust and it appears that's what these headers are. Well that helps me narrow my search for mufflers now. Thanks.
            -Theo

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