Inherited class, trying to overwrite variable.

So I have two classes. In one, any Motor variable can be used, but in the latter one, I only want CharacterMotors on that variable. Yes, while in the Setter, I could simply limit it only to allowing CharacterMotors, but I have to rely on references to the CharacterMotor class.

I keep getting "The type CharacterMotor' conflicts with the imported type CharacterMotor'. Ignoring the imported type definition.", and whenever I try to reference the CharacterMotor, I get an errors about the object not being set to an instance of the object.

How can I override the main class's _motor with my new _motor?

 public class MotorState : MonoBehaviour {
 
 [SerializeField]
 protected Motor _motor;
 public Motor motor {
     get { return _motor; }
     set { _motor = value; }
 }
 

}

public class BasicCharacterMotion : MotorState {

 protected new CharacterMotor _motor;
 public new CharacterMotor motor {
     get { return _motor; }
     set { _motor = value; }
 }
 

}