99 YZ400 JETTING W/ Big Gun Exhaust

Can anyone tell me what MAIN jet and what PILOT jet to use with this BIG GUN Race Exhaust setup?

well I run a big gun race on my 2000 wr400 the pilot is a 48 and the main is 180. Hope it helps Oh yea stock needle jet.

I've been between 180 and 185 on the main

Thanks I'll give it a try...Can I change it without taking the CARB out?

I changed it on my 426 without removing the carb. i just loostened the unit and removed my throttle cables and spun it sideways. got good enough access to it that way. i dont know the real diff between the 400 and 426 jetting but i too have a big gun exhaust and I run a 42 and 165 with a little tweek on the fuel screw.

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