Maybe some of you have some input for me here.
The bike is a 03 Raptor, no motor mods.
The temp is about 30 degrees.
The altitude is around 500'.
I'm running a modified Pro Circuit T4 that runs only a little leaner than the stocker.

I bought the K&N Powerlid. This is like a big K&N filter that replaces the airbox lid. It's supposed to be the next best thing to running without a lid. I ride in slop, dust snow, anything but heavy mudding so I don't want to run no lid. Also, since you run another K&N to replace the stock filter, you get extra filtration, which I feel is important in the fine dusty areas I ride. I've heard that a K&N is not the best in dust, so I feel safer.

K&N provides Mikuni jets to go with thier Powerlid. Thier instructions say use a 150-155 on the left and 170-175 on the right. Also both needles on the 5th clip down and mixture at 3 and 3.5 turns out. It seems like 4-5 steps apart on the two carbs is quite a bit, but I tried it with 155 & 170.

She ran so rich I couldnt even drive it. It was like the reverse rev limiter was stuck on in forward. I raised both needles to the 3rd position. Then its super lean until full throttle then its rich and stumbles. I go to 165/170, fourth clip. Rich all around but better. Backfires & stalls off idle.

Now I'm down to 160/165, 3rd clips. Half throttle is pretty good, maybe a tiny bit rich. Haven't been able to do full throttle chops yet cuz its late and I'm in the 'burbs. BUT! Off idle and especially after decelerating a while then giving it some more gas she still stumbles/backfires/stalls.

My questions are:

Could K&N be that far off? Why do they want 4-5 steps between the jets?
I'm still at 3 & 3.5 turns out. Is that way to rich off idle? Is it causing my low/mid throttle stumble?
I forgot what typical stock mixture screw settings are. Anyone know?
Could my mains still be too big for so much airflow?
What one thing would you try to improve throttle response first?

Thanks all!

 

I think there must be a misprint. I would say 155 lt. and 160 Rt. on the mains, 3rd groove on the needles. 3 to 3 1/4 turns on the idle mix screws. You may want to put in 25 pilot jets and go a little over 2 1/2 turns on the mix screws.

 

SixsixT, I was thinking I was already rich on the mix screws. I get none of the lean backfire on deceleration, but when I give throttle again after decel, she backfires and stalls. Am I wrong there?

 

If it's not popping at all on decell I would say your mix screws are a little rich and you might want to try turning them in or put them both at 3 turns and try it.