98 yz400 jetting for ice racing

any feedback concerning the jetting of a 98 yz 400 for below freezing ice racing conditions would be greatly appreciated.

Cold air is denser, so the thing to do would be to try just one size larger jet to compensate. Keep in mind that if you increase your pilot jet, this will richen the mixture throughout the throttle range since fuel is ALWAYS flowing thru the pilot jet. If it were me, I would keep the pilot jet and go one richer on the main jet, then you could adjust the pilot ciruit with the fuel screw. Making one change at a time and then testing that change, will get you going in the right direction. Making multiple changes at once will make you sterile.


From stock setting, go one up on the pilot, one clip richer on the needle and up to 2 or 3 up on the main.

You will have to re-adjust your fuel mixture screw.

When you run a dry filter like on the ice(to avoid clogging-up with snow dust and water) you will run quite lean with the stock jets.

I will check my log and tell you what I was running in my 99.

Have fun sliding around... :)

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