NEED help on 300ex jetting fast

[scott58976]

i need help on jetting my 300ex mods include:

297cc Bore Kit w/ 11:1 Wiseco piston
Precision Port and Polish/3-angle Valve job
HMF Full Exhaust system
K&N Air filter running with lid off

What are some good jet sizes for this setup.....im not sure what it has in it right now but i do knw that it is setup for a supertrapp exhaust and a UNI air filter and it backfires like crazy.......and if i decide to go back to UNI filter if i dont like the k&n am i gonna have to change the jets agian??? thanks for all ur help. this is by far the best atv forum out there

[bwamos]

Start with a 140 Keihin Main, 42 Pilot, 2.5 turns out, and Needle up 1 slot (from stock / clip down).

May be ok with the stock pilot at 3 turns out. But if you get backfiring on decel, swap it out to the 42.