Suggestions to help my '03 450 chug better

I am new here to this site. I have an 03 wr450 and was wondering why my bike (CA model) comes stock with a 45 pilot and 150 main jet? 2004 and up have at least a 165 main jet. As far as I know there is no difference between the 03 and 04 other than the pesky woodruf key right?.

I have a FMF powerbomb header and tail pipe, grey wire cut, snorkel removed,sides not cut out of airbox, and throttle stop removed,. Does anybody know why the 03 is jetted so lean? should I go bigger on the main jet to 160+? will it get worse gas milleage if I do?

I am new here to this site. I have an 03 wr450 and was wondering why my bike (CA model) comes stock with a 45 pilot and 150 main jet? 2004 and up have at least a 165 main jet. As far as I know there is no difference between the 03 and 04 other than the pesky woodruf key right?.

I have a FMF powerbomb header and tail pipe, grey wire cut, snorkel removed,sides not cut out of airbox, and throttle stop removed,. Does anybody know why the 03 is jetted so lean? should I go bigger on the main jet to 160+? will it get worse gas milleage if I do?

All CA models are lean for EPA 'reasons'.

160 main is about right, and your mileage will drop.

Thank you for your help, I think I will pull my spark plug and see what color it is. Thanks.

Thank you for your help, I think I will pull my spark plug and see what color it is. Thanks.

You can't really judge much by plug color, unless you use Race Gas ...... pump gas is filled with 'aditives' to keep it profitable and have longer shelf life.....and can burn brown, yellow, or black with the same jetting.

Seat of the pants or AF meter....or follow the stickies closely and copy a succesfull tune.

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