I've got an 04 Z400 and it recently sat for a while (2 months or so) and was rarely ran. Well, I drained the gas out of it and put some new gas in it. It runs funny now.. I was in 5th gear topped out and it started stuttering and spitting. Think this is a carb issue and it needs to be cleaned out?
Yes, most likely your carb has varnish in it, taking the bowl off and cleaning out the jets, needle and seat and it should solve your problem. (fuel starts to vanish after about 2 weeks without some sort of stabilizer)
btw, stabil usually keeps that from happening