Your first problem is that K&N. Those filters let way to much crap through to be on any ATV unless you run strictly sand. Get a good oiled foam filter. That said, pull the carbs off and clean them. All the crap getting by could be causing an issue. Keep the large rubber boots away from any carb cleaner, they will swell. Clean them with soap and water. Then let us know if it still gives you issues after the carb clean.