I think maybe a #42 pilot is too rich for 4000 ft. Try a #40. For what it's worth, I had a Dynojet needle in mine, and I went back to stock. Helped the jetting become easier to figure out.
Here's my set up.
168 main(keihin) a tad rich tho.
42 pilot
stock needle, 4th clip
2 and 1/2 turns out on air screw
no airbox lid
no choke
NEW RIDE.....
Houser Framed '02 CRF450 Hybrid. Powdercoated gold, chrome Houser sub-frame, Houser +4 no-link swingarm, +2 houser a arms, Houser stem, Tag T2 bars, +4 Dominator2 axle, Elka rear shock, Fox Float front shocks, Hardkore hubs, Dream waterpump cover, Dream clutch cover, Fullbore plastic, AC Pro-pegs,braided brake lines, and more....