My friend has a 2000 400 EX it has a K&N filter, 160 main, Big Gun /w quiet core. The problem is that when it is short shifted or lugged it loads up bad, and you have to pull in the clutch and clean it out. I think he has too much jet in it, and wondered what everyone else was running.
Oh yea we are at about 1800 ft above sea level.
Thanks Drew

 

That sounds OK. I run a 165 now and 170 in the winter.. Do you have holes in your airbox lid or have the lid off? I had to take mine off due to the fact at 3/4 to full throttle i would bog due to not enough air flow into the carb... Check your spark plug too..

 

For your setup and elevation assumming airbox lid on-stock pilot,air screw out one turn from bottom,stock needle clip position,152 main jet-with lid off,go to 155 main.that should do it.

 

Mine used to do the exact same thing. It went away when I changed the main jet to a 155 (from the stock 148), and I found a couple little chunks of dirt in the fuel-bowl plug, so I cleaned it out. I don't know if it's the larger main jet, or the crap that got cleaned out of the carb, but either way, it hasn't done it since. BTW, my only mod is I have the airbox lid propped open, so it's probably running a little rich.