Hesitation off idle

[acesfull]

I have a 2005 400ex and I put a white brothers e-series pipe, a k&n lid + filter, and rejetted to 170 from 148. It has a nice brown color on the spark plug like they do when 4 strokes are running nice, but when you open it up off idle or WOT from idle then it sometimes dies and sometimes is hesitates. What is wrong?

[nosliw]

i'd play with your jet needle some. maybe move the e-clip to the second position from bottom..... also do get a 42 pilot jet while your in there....

[acesfull]

I looked at the needle like it said to do in the installation manual but I guess the 2005 aren't adjustable. Can you buy longer or shorter needles? also what is a 42 pilot jet?

[Silverfox@C&DRacing]

I would change the pilot jet to a 42 and turn the fuel screw out a half turn.

[400exrider707]

Sounds like your rich on the main. Is that a new plug you put in, because it was probably brown colored from before. Put in a new plug and then do a full throttle test. Try backing off on the main and I bet it will go away.

[acesfull]

Where is the pilot jet, I just bought a jet kit that came with an adjustable needle, I put that in and took out my 170 main and replaced it with a 168, but I also bought a 42 pilot but I can't find where it goes.

[cals400ex]

are you running dynojets or keihin jets?

[Jonas]

Have you pulled the float bowl off before (the bottom end of your carb)? If not, you will need to in replacing the pilot jet. The pilot jet is near the main jet that you replaced but further down into the carb, if you are working with it upside down. It will look like the round slotted end of the jet they gave you.