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Hawk Racer Farting

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  • #1

    Hawk Racer Farting

    My Hawk road racer has a Mikuni fuel pump. The bike has a tendency to 'fart' or do a part back fire when on the track. It doesn't seem to affect performance and is only present 'off throttle'. Is this normal?
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    • #2
      suggest you inspect or renew sparkplugs
      "It's only getting worse."


      MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

      Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

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        • #3
          If it's only off throttle it may be related to the air cutoff valves, although those rarely go bad.
          ASMA #139

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            • #4
              Originally Posted by parillaguy
              My Hawk road racer has a Mikuni fuel pump. The bike has a tendency to 'fart' or do a part back fire when on the track. It doesn't seem to affect performance and is only present 'off throttle'. Is this normal?
              Ive seen a few that will pop off on deceleration. Have you given the carbs a good rebuild?
              Don't spend money and buy, spend time and learn.

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                • #5
                  Spark plugs looked a bit rich but were in almost new condition. I did switch to a mix of pump fuel and race fuel. Carbs use open bell mouth (no pod filters). No idea when they were last serviced.

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                    • #6
                      Originally Posted by parillaguy
                      No idea when they were last serviced.
                      I would start there. Give them a going over so you know what you are working with. Also check the carb boots while you have the carbs off. They get old and hard and leak air.

                      You dont want to chase a tuning issue that is actually a part failure.
                      Don't spend money and buy, spend time and learn.

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                        • #7
                          Carbs off and cleaned. I found aftermarket needles, 195 MJ and 45 pilots. I am thinking too rich and going to a 42 pilot and maybe 175 MJ.

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                            • #8
                              Originally Posted by parillaguy
                              Carbs off and cleaned. I found aftermarket needles, 195 MJ and 45 pilots. I am thinking too rich and going to a 42 pilot and maybe 175 MJ.
                              thats a LOT of main jet.
                              Don't spend money and buy, spend time and learn.

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                                • #9
                                  That’s a big hole and lots fuel, make anything fart.

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