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Honda CG125 Carb Rejetting

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  • Honda CG125 Carb Rejetting

    Evening chaps,

    As most other people seem to be at the moment, I'm doing a bit of a DIY cafe racer project and as I've removed the air filter box unit to free up space and tidy up the bike switching it out for an aftermarket pod filter. The carb is a Keihin carb. Pilot is currently a 38 and main is an 88. Does anyone with a bit of knowledge of rejetting have any suggestions for how many sizes to jump up on either one? Any help or advice would be ace, cheers!

  • #2
    Hi there. Unfortunately there’s no magic answer to this. It will be unique to your setup.

    Was it running okay with the stock filter?

    Have you got it to idle with the pod filter?

    My personal experience with jetting the CG125 for pods is here...

    ...and it’s still needs more work to be honest.


    • #3
      At the risk of coming across annoyingly dull, before getting too deep into tuning you will have to check that a few things are in order....

      1 - Inlet and exhaust valve clearances are correct.
      2 - cylinder has good compression.
      3 - ensure spark plug has good strong spark (full battery, ignition timing, points, new plug, etc)
      3 - throttle cable moves cleanly with no slack or snags.
      4 - carb intake rubber manifold is free from cracks or splits and seals correctly. No air leaks.
      5 - pod filter does not block passage in the mouth of carb and is fitted correctly.
      6 - exhaust is free from air leaks at cylinder mount.
      7 - tank is free of rust and petcock supplies fuel properly.
      8 - carb float level is at factory specification.

      Is it the stock exhaust you have?

      I bought a length of black hose that i’ve used to extend the pod filter a couple of inches away from the carb. I found the rubber of the pod filter was blocking the air passage that is located in the mouth of the carb. It also means the filter is not being pushed by the frame, which was causing splits, and finally it allows the air to flow better into the carb itself.