What jetting changes after changing the exhaust on ’02 WR426F

I ordered new MIK muffler with pipe to replace my restricted european model exhaust witch does not have a baffle and cannot be opened. So my question is will it be enough just to change the main jet from 165 to 170 that comes with my bike?

I do not want to brake my engine running it lean.

The bike is stock, no modifications.

Thank you for any input!

Sabin, your not too far off. Depending on the flow rates of your exhaust and your stock needle. You might also try raising your needle clip one notch. Does your model have the airbox lid/snorkle? If so you might want to remove it for better air flow. (replace for heavy mud conditions) Good Luck...


Thank you SoCol, but how do I know if I'm running lean? My spark plug is very white gray now, maybe it will become only white?

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