I got a 165 main jet with 3 1/4 turns out on mix screw, K&N filter, and yoshi slip on, i got airbox lid on and snorkel on. It doesnt pop anymore, but it cuts at 3/4 - full throttle. what do i do?!!

 

with the lid on you might have to drop a size on the mains. thats what mine was doing cutting out at almost full throttle. rechecked the jetting and runs fine now

 

so? a 160?

 

is 160 the next smallest down from 165? if it is try it

 

what about mix screw? some one told me it cuts, its lean

 

some ppeople are telling me to richen it up and itll be good

 

The carb has 3 separate circuits...any of which can be independantly rich or lean, from the others. Idle or pilot circuit ; needle circuit for the midrange ; main for 3/4 to wide open. Theres also a starter circuit, which the choke opens up.
The mixture screw will only effect idle. Doesnt matter what the rpms are, throttle position is all that matters.
Its posible the idle and needle are set correctly and the main is too rich, or too lean.
Try pulling on the choke while holding the throttle in the position it sputters at. If the sputtering improves or goes away...then the main is too lean. If the sputtering gets worse, the main is too rich. If this throttle position is 3/4 or more, open, then the circuit is the main jet, and changing it is the fix. Mixture screw has no effect on 3/4 throttle.

 

Just try taking the lid and snorkel off - The Z400 is a bit finicky about the intake moreso than the pipe.
If it runs better then it was too rich - this may be easier to do than rejet ?

 

ive ahd the id and snorkel off, i had to put them on becasue it was lean.

 

I wish I could help you but I just got my Z and the jet and yosh header and muffler were already on there. I don't know what size jet is in it, but it runs like crap with the air box lid off. It is very powerful with the lid on. I would take the snorkel off and try it with the lid on. I wouldn't run it anywhere I had to use a snorkel. That's what the utility atv's are for. I'll probably have to put a new jet in when I get my K&N and outerwear kit.