Jettin PLZ HELP NOW

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My bud needs to jet his 400ex. it is all stock right now and he is gettin a big gun system, a Kand N air filter with outer wears, and is takin off the air box lid. The average tempature here is about 92 degrees. ANY HELP IS APPRECAITED! thanx

[cals400ex]

a 155 to 158 should be in the ballpark. if you want easier starting, get a 42 pilot jet.

[H440exconfused]

Originally posted by cals400ex
a 155 to 158 should be in the ballpark. if you want easier starting, get a 42 pilot jet.



What he said.

Maybe a 160 but it is really hot there so prolly a 158 will be right on:

[cals400ex]

i was not sure if you were getting just the silencer or complete. i know you said system but i was just making sure. my friend has the slip on, K&N, with lid on in summer a 152 makes it fly. without lid a 155 is great for summer. for complete system, i would say 155 with lid on and 158 with lid off in summer. for winter riding i would go up one size on each of these #'s. good luck

[H440exconfused]

Its so hard to say but all I have to say is start rich and go down, my cuz called me last week, he has an 02 400 ex with Full FMF power bomb systemK7N and no lid, he said he rejetted to a 155 and when he started it the header pipe glowed orange that night so he had to go up to a 165 and it screams, he even won his class at the sod drags last sunday, and its right around 90 degrees here. I would say start rich and go down from there. If its a full systems i personally would start with the 160 and work my way down 158 and so on. needle on stock position.

Just my .02

[brink400]

I have the EXACT same setup as your friend. I had a 155 jet in there which was giving me some problems, so I went up to a 158 which works quite nicely.

[cals400ex]

my headers were glowing too while i was riding at 1/4 and less for any extended period of time. this means it is my pilot jet. i turned my fuel skrew out a turn and no more glowing for me. i first put in a 165 when i had my x-6, uni filter, no lid, and no choke and it was slower than stock. i went down to a 160 and that opened her up. its a close call between the 158 and 160.

[hondarider2006]

I am using a 165 right now. The temp is around 50-65 degrees right now, but this wither I will be riding at temps as low as -25. So I am sure the 170 with be coming in handy....

[cals400ex]

Originally posted by hondarider2006
I am using a 165 right now. The temp is around 50-65 degrees right now, but this wither I will be riding at temps as low as -25. So I am sure the 170 with be coming in handy....


How in the heck can you ride when it is below zero? Once it hits about 20 degrees, that is too dang cold for me. :D