I just thought I'd post my settings to help out anyone with my set-up.
2004 Honda 400ex - K&N filter, modified lid, stock exhaust with tip opened up, Sparks timing advance.
My carb: 155 Main, 42 Pilot, shim washer under the 3rd clip position of the needle.
Runs great! A lot more power than stock. Plug shows it's close to being tuned correctly. At or near sea level.
2004 Honda 400ex, 2003 Polaris Sportsman 700 4x4 lifted, 2003 Yamaha Raptor 80 (kids), 2000 Yamaha YZ250, 1993 Suzuki DR350s, 1985 CR250R