i have a 05 yfz 450 that sat outside all summer with the same tank of gas.  I  started it and it ran for a few minuets and quit.  I drianed the tank (the gas was really yellow, like apple juice) and put new gas in but it still wont start.  What do i need to do to get rid of the bad fuel in the system.  

Hmmm...I wish I could help you. I'll ask my dad & brothers they would know.  

take the carb off, remove the bowl on the bottom.
look in it and see if there is water, i'd just about bet you money there's water in there from condensation.
drain the carb, wipe it out use a wire bread tie and clean out all the holes an d jets.

put the carb back on make sure you are getting gas out of the fuel tank on off fuel valve if not take it apart and clean it too.