Best fuel mixture for yz 125?

So im getting a 2004 yz 125, I read that 32:1 Is the recommended fuel mixture ratio. But I live in florida and am only trail riding for now. Will hopefully start running tracks in summer. But I heard you have to open or close the pilot air screw I believe. Im a beginner rider so im not quite sure what I need to do. So what kinda of ratio should I run for trail riding? Might rev the engine high on straights. And should I jet it before riding? And what to do with the pilot air screw?

Thank you all.


  • Get a owners manual and READ IT! Do this before you ride.

  • Leave the pilot air screw alone, you don't know sh!t so why start screwing with sh!t you don't know?

    32-1 should be fine if running a good-grade 2-stroke oil. That ratio can be increased to 36-1 if it appears to be running too lean on the fuel and too rich on the oil but you'll need to know how to inspect the spark plug to know for sure.

    I recommend that you switch to a synthetic oil that will run 45-50: 1 for better performance and a bit cleaner burn. Bit more expensive in the short run but it all works out in the long run by better performance, less chance of fouling the plug and, I believe, longer ring/piston/main-bearing life.

  • I run 40:1 synthetic.

  • i think a 40;1 mix is alright but 32;1 plays it safe also... try an outboard premix this seems a little unorthodox but it protects against rust a moisture which is smart be sure it says its applicable to motorcycles

  • I would call the Yamaha dealer and ask them to Be sure . But I think you are right . Good luck & be safe !

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