on the left side of the sled by the fuel cap you will see a rectangular shaped piece with a slot on one end. pop this up and you will find a bolt head under there, 10mm, that secures the airbox to the frame. easily missed.
So just take the carbs out and the screw out that holds the air box in and it will fit out with out taking anything else out ? It looks like theres not enought room for it to come out without taking more off ?