The valves are probably the main thing to be adjusted as they can tighten up.
It would be hard to find a service manual for a Rancher 400AT online for free, unless someone on here would have one and would send you a copy.any idea where i can get the service manual for FREEEEE lol ? alos before i do anything I am going to have another person listen to it. because am not sure if its just me being picky and over listening to the motor.