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Exhaust for 50 Champion six

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  • Exhaust: Exhaust for 50 Champion six

    I recently got my 50 Champion running again after a lengthy hiatus. Among other things it is time for a new exhaust system. The stock pipes have always seemed small to me. I'm guessing there would be some advantage to going to larger pipes. How much larger should I go and at what point will there be negligible performance increase per dollar?

  • #2
    I doubt there would much improvement at all, and No noticeable difference between 1 1/4", 1 1/2' and 1 3/4" Pipes.
    But I would make them all the same size all the way back, instead of those tiny Tail Pipes.
    The Stock pipes would have been sized to the amount of flow from a 169 Engine.
    StudeRich
    Second Generation Stude Driver,
    Proud '54 Starliner Owner
    SDC Member Since 1967

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    • #3
      I use stock sized pipes, but install a turbo muffler in place of the standard one. Better flow and not much more noise.

      I recall reading something about a certain amount of back pressure being beneficial, but do not know the where of why of it.
      RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.


      10G-C1 - 51 Champion starlight coupe
      4H-K5 - 53 Commander starliner hardtop
      5H-D5 - 54 Commander Conestoga wagon

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      • #4
        If the exhaust system is modified to reduce back pressure, improve flow, then the carburetor jetting must be changed to match that; there's no free power.

        FWIW, back in the bad old days, I had a Triumph 650 motorcycle. First thing was to buy megaphone exhausts for it. Sounded great, ran slower. Went back to the shop and the owner saw me come in and held up a carburetor needle for the Amal carburetor. "Knew you'd be back for this." I asked, "Why didn't you tell me I'd need to rejet the carburetor?" He said, "Some lessons you need to learn first hand; otherwise, you'd just think I was trying to make more money off you."

        jack vines
        PackardV8

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        • #5
          I had two Triumph 650 Bonneville bikes, a 70 and a 72. Sounds like yours was a Tiger - only one carburetor.
          RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.


          10G-C1 - 51 Champion starlight coupe
          4H-K5 - 53 Commander starliner hardtop
          5H-D5 - 54 Commander Conestoga wagon

          Comment


          • #6
            Originally posted by RadioRoy View Post
            I had two Triumph 650 Bonneville bikes, a 70 and a 72. Sounds like yours was a Tiger - only one carburetor.
            Yes, Roy, that one was a single carb. I had several Bonnevilles also. The one I liked best was the '65; it steered and handled much more responsively. Around '67, Triumph changed the frame and steering head geometry to slow down the turn-in and make it more of a freeway cruiser. The later bikes were not nearly as much fun to ride. Again, around 1970, they came out with a new frame, new front and rear brakes.

            I built a cafe racer with Ceriani forks, the '70 front and rear brakes and an aluminum oil tank. The engine had 750 cc barrels, Sifton cams and Dunstall exhaust.

            jack vines

            PackardV8

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            • #7
              Originally posted by PackardV8 View Post
              Again, around 1970, they came out with a new frame, new front and rear brakes.

              I built a cafe racer with Ceriani forks, the '70 front and rear brakes and an aluminum oil tank. The engine had 750 cc barrels, Sifton cams and Dunstall exhaust.

              jack vines
              The new frame was in '71, bought a Tiger new. Didn't like it much, and ended up crashing it into the side of a '59 Chevy wagon that turned left in front of me. And I'll bet that was a nice bike, Jack.
              3H-C5 "The Blue Goose"

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              • #8
                Thanks, guys. This is great information.

                [ If the exhaust system is modified to reduce back pressure, improve flow, then the carburetor jetting must be changed to match that; there's no free power.
                jack vines ]

                So will I need to go richer or leaner? I'm sure my 72 year old needle and jet are already a size or two rich. I haven't had any luck in the past finding new jets or needles.

                Hank

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                • #9
                  Hmm?!? Doesn't this post generate some food for thought!

                  My 1951 Champion is being mounted in a BOAT (the original motor was a '49 Champion which ran the boat successfully for 25 years). At start-up and when idling or moving at very slow speed, the exhaust pipe is UNDERWATER!!! As a matter of fact, despite having a rubber flap over the end, at start-up, I would imagine the lower exhaust pipe is FULL of water until the exhaust blows it out!

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                  • #10
                    Typically, improved exhaust flow leans out the mixture, necessitating a richer jetting.

                    However, anyone wanting to get it right should have a wideband O2 sensor at hand.

                    Also, as often mentioned here, it's common for seventy-year-old carburetor to have worn throttle bores in the casting. If it's leaking air around the shafts, idle mixture adjustment will be problematic.

                    jack vines
                    PackardV8

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