400ex problem

[dnj400ex]

I know a lot of these quads are cold natured but mine is excesive. When i first start it, it will spit and sputter and eventually it will backfire very loudly through the exhaust. After about 5 to 10 minutes of warm up, it runs fine. Also, I am fouling a spark plug about every 2 trips. Please help.
Here's what I have. 2002 400ex, engine stock, white bros Eseries slip on, K&N filter, Stock needle, stock pilot, 160 main (dynojet).
Basically, I would like to start this thing and let it warm up on its own. Right now I have to start it and immediately rev the engine for about 5 min before it will idle.
Thanks

[phatman]

put a 42 pilot jet in . you just pump it 3 times and she will hit. air fuel screw at about 2 turn out

[phatman]

you will not need to use the choke

[CBR954RR03]

Sounds to me like you are putting TOO MUCH fuel to it.. I have the following mods and retained the all stock jetting and needle:
- WB e-Series Pro-Meg with Head Pipe
- WB Foam air filter (came with Pro-Meg)
All on a stock motor and I'm running 10 disks on the WB and it starts right up without a problem and idles great.

If you have the tunable exhaust, look into changing the amount of disks you have on it.... I put mine on with only 8 disks to start and fouled the plug instantly, it wouldn't even start.

just my .02