Two stroke jetting

Hey everyone! I have a 2004 yz125 and I'm thinking of doing a jetting adjustment. It runs good in the winter with low smoke and when the choke is on it revs up a lot. I heard its called lean runaway. The plug is just black from carbon, no oil or gas on it, no ash. just black. It gets awesome power and nice throttle response. I don't have a clue what a properly jetted machine should feel like. How exactly do I jet a bike? I have carbon fiber reeds, not sure the make, maxima foam filter, and doma racing pipe

Choke on, high revs, is normal

That is not 'lean runaway idle' because the choke makes it rich.


Jetting a two stroke takes YEARS of practice and learning.

Your best bet is to go to the Yam two stroke forum and ask questions.

Be prepared to tell them every thing about your motor and carb, or you will get no where.

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