what i've got> 03 z400 w/ full comp yoshi and prodesign proflo kit..
mechanic recommended main jet to 180...was previously at 160 with no problem..mechanic said 180 would do better...so i did it..now that i've done it, it doesnt idle evenly and sort of studders and backfires a little when u kill it...is it too big of a jet, air/idle screw, or do the valves need to be adjusted since i've never done that in the year i've had it...thanx

 

180 sounds WAY too big to me!!! Why did he suggest you change it? If it was running good before I would put it back. I haven't heard of anyone running that big of a main..........

 

180 does sound big, if it's idling bad increase your pilot jet, not too much though! If still bad a 170 will be plenty big and you won't have to adjust your pilot jet. Good luck

 

well i thought the same thing guys, but long story short, i'll try just about any combination once just to see what the result is...ya never know

 

put it back they way you had it.... if it aint broke dont fix it... right?
different combinations may make it run better... but when its jetted right.... its right... you cant make it better.

 

I run a 170 at sea level and it is great. I would try that before going back to a 160

 

Take the lid off and the 180 will be perfect!!! I guy i ride with has a kfx400 with full lrd system and a uni filter and no lid jetted at 185 and it runs 100% perfect.