Buck, Just to give you a point of reference on my jetting for a 42 mikuni with agressive dune porting and a Q pipe- and I am at 5000 feet.
My pilot is 30---I have read that on the zillas a pilot jet on the fat side is easier to start than one thats on the lean side
Main jets are 450  with no air box and 9" filter.  I dont think a fat main will have effect on starting (but it may) but you are going to be way fat on that 580 main.  Ask kenners or rider 414 what they run jetting on their Q pipes.   Seams everything I have read the Q pipes do not runtheir best with 550 600 mains like some the HPR pipes.  Float heights OK? Carb filling with fuel? Bad Plug?--just thinking outloud.

After my rebuilds or if it sits for month with out riding I have to tow it around behind another atv or car in third gear 50 to 100 feet to get it to fire and clean out--then it runs and starts great. Tow that Biatch.