which jet combonitation.

[400EXracer74]

currently i have a 170 main jet in my 400 ex and i think a 45 pilot jet. it runs good all the time but i dont know if thats just cuz it is running lean. ive heard lean runs fast and hard bust isnt good for the 4 wheeler engine. i dont know if this makes much sense but i also dont want to do anything bad to my engine. i have an FMF powercore 4 exhaust k and n filter and no air box lid.

[cals400ex]

if your running keihin jets, i wouldn't run larger than a keihin 158-160 in cold weather and low elevation levels with your setup.

[Screamin440]

Lean is mean but fat is happy. I prefer mine a little on the rich side to keep cylinder temps down and to prevent pinging.

[400EXracer74]

i have a dyno jet 170 in and its warm. ya think thats ok?

[TravEX]

http://www.cdracingonline.com/id57.htm

[cals400ex]

i haven't tried dynojets out but from what i read a dynojet 155-160 should be plenty. your bike may seem to run fine now but it should run better by going a little smaller. good luck