So i have checked my spark plug. replaced it, got a new battery. drained the gas tank. checked the carb, and that is everything i can think of but my 400ex still won’t start. but it sounds like it wants to and i don’t know what else i need to do, i have also added more oil and changed the oil filter. i don’t know what else to do. i need some advice.

 

When you write "checked my spark plug" have you checked if there is a spark when you spin the engine over on the starter? This is the first thing to do, as no spark means a faulty ignition component or wiring.