jetting for 99 wr 440 with big gun system and 95db core

[city boy]

i have a 1999 wr 400 with a 2001 yz 426 carb and cam timing set to yz spec

just installed a big gun system with 95 db insert , i ride at sea level and jetting in the carb is all stock 2001 yz426 . what jetting should i have , runs fat now.

thanks

[Wayward Son]

describe what you mean by runs fat now?

[city boy]

After I installed the exhaust system, I took it out for a test drive and at third throttle the engine would blubber (like it would studder). I pulled the choke on and it made the studdering problem worse. I came home and I dropped the needle one notch--putting it at the third from the top--and took it out for a test drive. That seemed to solve the studdering problem...I ran it in fifth gear for about 1/8 of a mile at wide open and the header pipe turned bringt red. So I changed my main jet from a 158 to a 168, took it for a test drive and the engine pulls a lot harder at the top end, but it wasn't dark enough outside to tell whether or not the header pipe was turning red or not. Right now I'm at 168 main, stock pilot jet, 2 turns out on the air fueler mixture screw, and BTW, I'm fighting off an off-idle stumble--like it's lean--no matter how many turns in or out the mixture screw is at, I also set the mixture screw at what seemed the best idle. The needle number is a OBEJP....Would a JD kit take care of a lot of these problems? Power Now?

Thanks

[Wayward Son]

the jd kit would be a good choice.

a EMN needle would also be a good choice.

your head pipe was glowing while you were driving at wot or when you were sitting still after the wot run?

[city boy]

while i was riding

[Wayward Son]

the insert may be the cuplrit.

[city boy]

so change over to a jd kit or a emn needle and on the main jet go by plug reading or air/fuel reading [ like 14 to 1 ] or ?

thanks

[Wayward Son]

you need a wide band air fuel meter if go that way. 13.0 to 1.