ATV Florida Forum

i have a 2002 400 ex with a white bros slip on k&n filter and k&n box lid
the kit came with a 168 and a 170 main jet just wanted to know where should i bee on
fuel air mixture it was at 2 1/2 turns out and it was running crappy so i turned it in 1 full turn
is that OK  

as you can tell i dint know what i am doing but i am hand and wanting learn

put the 170 main jet in    so u got the adjustabilty of air fule screw so if you ride in diff spots or temp changes   find the point were it puffs no smoke and nice and clean revs thouh power band no poping either

disregaurd what the above poster said, he thinks a 400ex is a 2 stroke for some reason. your bike shouldnt smoke, hes thinkign 2 stroke lol.

just put the 170, its not a big deal. theres practically no difference in a 168 and a 170.

just put the air fuel screw to stock and play with it in about 1/4 turns until you get it to have good response. the air fuel screw has to do with how quickly the carb responds, if its sluggish just play with it until tis nice and snappy.

chevy drivers cant read anything lol :-\  i guess i did not word it goodenough he said the same thing i did o well at least i knew i was right first  ;)   chevy1500z71   its ok ill give it to you this time but yes i do no that bike is 4 stroke  its honda version to the kfx400 in the same class   but it is air cooled not liquied cooled

looks like me and you got same bike 05 kfx  400 when u wana run?

how many turns should i start with right now i am at 1 1/2 turns it was at 2 1/2 turns runs better at 1 1/2
still dont know if its right still popping a little i just want to make sure i dont burn anything up

ps thanks to all helping me i am a newbe but larning alot from u guys thank so much

is that dyno jet or something other than keihin?  look at my mods and I run a 42 pilot, 158 main, and needle on the 3rd slot.  it runs pretty perfect.

That screw your messing with is your idle air mixture and won't change anything above half throttle ( i am more than sure it only affects idle since your slide is closed until you start gassing it).. where are you running crappy at?
Read your plug and see if it is running rich (black and sooty).. if so, you need to go down in jet size, if it is white, you are running lean and need to go up..

fuel air mix was at 2 1/2 turns out ran like sh*t half throttle snapping and poping
 
fuel air mix is at 1 1/2 turns out runs better

does it smooth out past half throttle?

Here is a pretty good article on how to adjust that screw properly, if you are having problems mid-range + it is your main jet, if not, try this:

http://www.thumperfaq.com/mxa_thumper_fuel_screw.htm

Its not specific to your bike, but it is they way all 4-strokes are done (it even does a little explaining of the difference between 4 and 2 strokes)

Also remember that it is getting colder outside and what you set it to now may no be optimal when it warms up, this becomes more and more apparent when you do more performance mods.

getting better i came out 2 turns runs good but backfires when i let off can any on help!!!!!!!!!!!!!!!!!!
still have the 170 jet