I have a 426ex. hotcam stage 2, k&n, over rev box, ported and polished, LRD full system, and airbox cover cut in half. I bought it like this 2 years ago and I have known all along that it runs too rich on the top end. It runs very strong (kills my buddies raptor) but will not hit the rev limiter. (I am not a rev limiter freak but from years of streetbike experience I know the jetting is off). It has a 170 main in it right now...All I want to know is what main people with a similar setup are running. Please dont respond with a bunch of "try this and that" I'm not being rude but I would like actual answers from people with a similar setup. BTW the plug is black.

 

i'm running a 170 main dyno-jet jet with all stock internals. i've got no airbox, slip on suppertrapp exhaust stage 2 dyno-jet kit, and k&n filter. i've been told though that dyno-jet jets are not equal to other jets of the same #. not for sure but just what i've heard.

 

I've heard the same thing.

 

muddstudd is correct, the largest jet that comes in the dynojet kit is numbered 170, which is actually larger than a kehin 170 jet. I do know that the DJ 170 is smaller than a kehin 200 by a bit.
zx9rbart, is your main jet hex type or slotted for a screwdriver? DynoJet jets are slotted and the kit comes with an adapter. With the setup you mentioned, BOTH 170's (DJ and Kehin) would be way too lean. Your problem lies elsewhere. Check for a clogged air filter, carb float level, and needle position. Also make sure you're running a stock carb, or all bets are off.
I run a 215 Kehin main in mine when I use my modified lid and the plug is tan, I could probably even run a 220. My engine setup is milder than yours too. When I'm mudding I put the stock lid on the airbox and I put in my Dynojet 170 main to compensate for the restriction of the lid.
Keep in mind I'm at sea level.