i need some help jetting my 400EX

[jason jacobs]

I just got a new big gun complete exhaust and also i'am running a k&N with no air box lid and i just can't seam to get the jetting right any help would be much appreciated thanks

[GNCC#829]

What is "not right" about it? Is it backfireing or bogging?:confused:

[cjames235]

sorry to hyjack your post but i also need some help with this but i have a yoshimira slip-on with k&n. if i put the lid on it runs fine but if i take it off it bogs on low-end when i blip the throttle from idle. i have a stock pilot and a 148 mj with needle at #3. i have also tried a 155 mj and it did the same thing. what could i do to take care of this? thanks for the help

ps- i have the dynojet kit and it only has mains no pilots.

[RAPTORAZ]

What's your elevation?

[cjames235]

im at about 420ish ft above sea level

[RAPTORAZ]

Originally posted by cjames235
im at about 420ish ft above sea level

Without an airbox lid, you need more like a 165 main, a 42 pilot, and the needle needs to be moved up one position from stock.

[cjames235]

oh yea im also running the mixture screw at 3.5 turns out. does that sound right?

[RAPTORAZ]

I set mine by ear. Didn't really pay attention to how many turns it was. To set by ear: Screw it out until the exhaust starts getting stinky. Then screw it back in until it develops a lean miss. And then adjust it back out until the lean miss goes just away.

[trailburner]

I'm running a 160 main[K&N with lid off] with my mods & it's running fine[nice color plug].....

[cjames235]

hey raptoraz how do you adjust your mixture screw while it runs? i cant get anything in there to even turn it without takin the carb off. any help with this is greatly appreciated

[RAPTORAZ]

A 90 degree angled ratcheting screwdriver. It aint easy, but it's doable.

[cjames235]

how do you get around the idle adjuster flex tube thing?

[RAPTORAZ]

It's been a while, but I'm pretty sure I did it from the other side with an ink pen taped to the ratcheting screwdriver as an extension.