currently i own an 03 z i have a intake and a full pipe on it whats the next few mods i should get without making the bike less dependable. carb or the athena big bore. i understand the big bore will make the quad alot faster but i know they make them less dependable and i dont want a bike that needs work evertime i ride it. the carb will add a little power but how much less dependable will my quad be. i also have another problem i dont know if its the spark plug, batteries or the z400's in general. sometimes it doesnt fire right and it likes to stall unless its fully warmed up and that takes about 15mins. other times when it sits for a few wks it has alot of trouble starrting and with my 250ex i never have problems with it starting.

 

Was the bike re-jetted when you put the pipe and k/n was put on?? Just asking.

 

I'd do the big bore and a set of cams and a new cdi for it, if you have enough green left then have it ported and have the valves redone while the heads off. as for the other question check you jetting and if its been a while put a new plug in it ,