Are you still getting spark? What is the quad doing other than not starting? Any engine needs three main things. Fuel, Air, and Spark. Fuel is a given as long as your tank is full and it's going through the carb. Air is another given, but also includes proper compression which can be an issue. Lastly, is spark. Could be the coil, stator, or plug. More info is needed to diagnose where to start looking.