I was told Honda jetted the 400ex on the lean side to reduce emissions. Thats why its hard to start. If you get a pipe and rejett it will start and idle much better.

 

i retract my last comment. now i have the following

42 pilot
sparks X6 pipe- if you want a pipe, i know its expensive but man the power is better then all of them, and i have a HMF on my vinny, i think the sparks is made a BIT better.
needle is on stock clip, and a 155 main, im trying to perfiect it, and am going to get a EHS lid, so i am waiting for that till i rejet again, but for the time being, full choke, starts right up, put to half choke, idles so much better, i mean it will almost idle, but i keep my idle on the low side for when it is warm, and when im stopped.

v581