Need help jetting

[supermans400ex]

I'm running a white brothers r4 full pipe with wb air filter, lid on. I"m in alabama not so sure the elevation but i was wondering what size jets should i run?

[kegger56]

Thanks supermans400EX for bringing this up cause I have the same question. What should the jetting be for a 300ex with full FMF exhaust, K&N airfilter w/ airbox lid removed riding at sea level. Sorry if it seems like I'm Thread Jacking, but I figured I'd piggy back this one instead of opening essentially the same thread!:D

[cals400ex]

with knowing what you both told me i would start here:

400ex--
Keihin 155 mainjet
stock needle clip position
42 pilot jet
2.5 turns out on fuel screw


300ex--
Keihin 135 mainjet
i don't know on the fuel screw or pilot jet. i don't have a 300ex but i hear many people put in a 40 or 42 pilot jet too.

[kegger56]

Right on cals400ex now I have somewhere to start!

[supermans400ex]

Thanks Cals400ex, If i didn't change the pilot jet out, would it hurt my performance out much?

[cals400ex]

Originally posted by supermans400ex
Thanks Cals400ex, If i didn't change the pilot jet out, would it hurt my performance out much?


nope, it would just be harder to start without changing the pilot jet out. if you don't change it out, i would turn the fuel screw 3-3.5 turns out from lightly seated.

[supermans400ex]

Alright,thats what i needed to know.

thanks

[LsMxRaCeR]

i have a 400ex and am about to get a big gun full system and i was wondering what jets i should use