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Bought a Supertrapp for my GS400/425/450 MAC exhaust, here is how it went.

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    #16
    not to hijack your thread, but I'm looking for a similar replacement for my MAC muffler:



    very cheap, but I'm gonna need to muffle it somehow I'd like a little more sound over stock, but I don't want to be annoying everyone in a 2 mile radius. motorcycle baffle and baffle insulation would keep the noise down?

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      #17
      So, here is a question:

      I have a supertrapp pipe and stock jetting, how do I know how many discs to put in to get the pipe in it's "happy place" before I start carb tuning?

      I started with 6, seems to run great, tried 5 just for s&g and it seems to tame it own a bit so I am pretty sure going lower isn't right. And 6 is already about as loud as I want it.

      So is that ok, anybody with a supertrapp have any tuning advice?

      Are 120 jets a good starting place? Stock is 117.5. I will do some official plug chops soon enough, unofficial ones look the same as before, black ring and bottom fading to a dark grey at the top of the electrode.

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        #18
        I would go with six discs if that 's an acceptable noise level for your ear. Most 4 into 1 (V&H, SuperTrapp) aftermarket manufacturers recommend bumping the main jet by 3 to 4 sizes. Since you are adding a Supertrapp muffler to your stock 400 head pipes bumping the main jet by one size is probably a good starting point. You probably wll have to tweak the air screws etc to get transitions right. When you perform plug chops I would mark the the throttle grip to locate 3/4 open and make sure you reach that point before drawing any main jetting conclusions.

        IMO & experience adding/removing one disc has no effect on overall jetting.
        Steve

        1979 GS1000E (45 Yrs), 1981 GPz550 (11 Yrs)

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          #19
          Originally posted by srsupertrap View Post
          I would go with six discs if that 's an acceptable noise level for your ear. Most 4 into 1 (V&H, SuperTrapp) aftermarket manufacturers recommend bumping the main jet by 3 to 4 sizes. Since you are adding a Supertrapp muffler to your stock 400 head pipes bumping the main jet by one size is probably a good starting point. You probably wll have to tweak the air screws etc to get transitions right. When you perform plug chops I would mark the the throttle grip to locate 3/4 open and make sure you reach that point before drawing any main jetting conclusions.

          IMO & experience adding/removing one disc has no effect on overall jetting.
          It is a MAC 2-1 header, OD seems the same as stock though. But into a 2" collector/pipe.

          so just to confirm, mark throttle at 3/4 and make sure to go at least that high (not WOT?) then kill the engine and pull the plug?

          also I have heard conflicting info on whether "one size" is 2.5 "numbers" up or 5? Guy at the bike shiop I bought the jets from says that going from 117.5 to 120 is just "half" a size up.

          I will try the 120's, see what happens and go from there, might take me a couple weeks though haha.

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            #20
            Hmm, i went back to 6 discs, it is a bit louder, and it SEEMS to go better, is this just my ears telling my butt it's going faster?

            Honda Civic syndrome?

            I have never heard a bike that sounds like mine, not that it sounds better than any other bike I have heard, but it's different

            I read the manual that came with the can, it says that I should "tune it for stock" and then jet up later. Is it possible to tune my setup for the stock jets until I have time to mess with the carbs?

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              #21
              Why don't you ignore the top mount completely & get a nice bit of AL or stainless to make a strap to mount it on?
              That way you only need to use the mounting bolt & all you'd see from the side is the strap going round the muffler.
              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..... - FOR SALE!

              www.parasiticsanalytics.com

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

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