Home Forums 2-Cycle Racing Use Yamaha KT100 pipe on HPV/KPV engine?

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    • #79816
      Caleb Gilbert

      I know that people run HPV pipes on KT100’s but can one do the reverse with good results?

      I ask because I have a brand new’ish Formula-Y pipe for my KT100, a HPV 2 pipe, and an HPV 4…..what I would really *like* to have is a HPV 3, but do not want to spend anymore $$$ and it seems that theoretically my Formula Y pipe would be a nice substitute for the HPV 3 (they are both pipes built for low-end power).

      In case anyone is wondering – do not want to run the HPV 4 btw because I want to keep the revs of the engine down for maintenance reasons (it’s widely accepted that a engine with a HPV 4 is going to need to be wound to higher RPM’s than the other pipes).

    • #79823
      William Martin

      Interesting thought, I expect it is off the beaten path enough that you just have to try it & see. Keep the carb extra-rich until you know how much torque you are getting from the FY pipe. I expect it is a wide, as in non-peaky power band, which is good for an experiment. Not as likely to melt a piston as a peaky pipe! If you have an egt gage on your HPV, it will tell a lot about how to tune for that pipe.

      Best of Luck,


    • #79831
      Brian Patterson

      There’s very little difference between the 2 and 3 pipe. If you run a shorter flex, you will get the same result. If you read the IKF rule book, it gives you all of the dimensions. The only difference is the volute. Use a 10-10.5″ flex and get the same result as a 3 pipe with a longer flex.

      Check the rules section of Tri-C Karters or F100 karters for the direct flex length comparison.

    • #79863
      Caleb Gilbert

      Wow, thanks Brian for such an informational response. I actually received two HPV-2 pipes with the used engines I bought, so the flex change and the 2 pipe sound exactly like what I’m looking for.

    • #79865
      TJ Koyen

      Will +1 that the HPV2 pipe is very similar to the 3. I remember when we switched, could barely feel a difference.

      Driver/Coach/Wrench : Innovative Performance/Exprit
      Owner : Oktane Visual - www.oktanevisual.com

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