Home Forums Shifter Karts What is required to do a pump around mod?

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    • #47004
      Taavi Koppel
      Participant

      Hi,

      I currently have a fuel pump that has a rocker arm leaning on a cam on the rear axle.
      If the rear axle spins faster the pump goes faster.

      Major drawback is that the kart is not able to run for a long time if its stationary like on the start.

      What if I just buy a pulse driven fuel pump and feed the carb like that without any modifications to the carb? Will it work?
      What mods are done to the carb when doing a pump around mod?

    • #47156
      Ed hodgson
      Participant

      I have a pulse driven pump on my kart, and it works well. (It feeds a Mikuni TM-28 carb on a Honda CR 80 engine). The important parts of a pulse pump setup are where you source the pulse signal from, and making sure you route a return line back to the tank.

      On a single pump setup, most people utilize a tee off the outlet of the pump, with one side providing fuel to the carb, and the remaining side being used as a return, otherwise you can run into flooding issues.

      I believe a pump around setup is accomplished by removing the floats inside the carburetor, and utilizing 2 fuel pumps. One pump sends fuel to the carb, and the second pump returns fuel to the tank, so that it doesn’t over-fill and flood the system. They are more complex than a standard, single pump/return line setup. Plenty of reading on this great forum about both systems.

      I personally have not used a pump around system, so I can’t tell you much more than that, and if I have misinformed you in any way, I apologize, and hope that a pump-around user can further enlighten you

    • #47191
      Scott Newton
      Participant

      I used a pumparound on my CR125 – it was just two standard Mikuni pumps, one pumping from the tank to the carb, and another pumping from the carb to the tank. Both pumps were driven off a pulse line from the engine. I don’t know if the carb was modified at all, since the carb was previously used in a pumparound setup before I got it. The system was 100% trouble free for me, and other than having twice as many fuel lines and fuel pumps, didn’t look like that complex a setup.

    • #47197
      Taavi Koppel
      Participant

      What I dont understand is why the second pump in needed? If you just split the fuel line with one going to the carb and one back to the tank it would work just the same. If the valve on the carb is closed no more fuel goes to the carb and the exess is pumped back to the tank.

      But it might have something to do with cornering. These carbs are originally made for dirtbikes and taking corners with these keeps the fuel level in the carb because the bike tilts when cornering. The kart does not tilt, the carb does not tilt but the fuel in the carb tilts when cornering.
      Where from the carb is the second pump taking the fuel out?

    • #47198
      Scott Newton
      Participant

      The single-pump setup you’re describing would work – and is the standard setup, but it’s not a pumparound setup. With a pumparound setup you’re removing the floats and needle valve, and instead using the second pump to siphon off the excess fuel from the fuel bowl. The pumparound setup is to prevent possible fueling issues due to sticking floats in hard cornering or bumpy situations.

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