How to make pinball flipper

I am trying to make a pinball game but am having difficulty with the flippers. I have tried to attach motors to the flippers and then used a script to change the motor speed, but so far, they only move when I change the speed in the inspector, not from the script.

This is my code so far:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Paddle : MonoBehaviour {
     private Rigidbody2D rb2d;
     private HingeJoint2D jointRef;
     private JointMotor2D motorRef;
     public float speed = -100;
     // Use this for initialization
     void Start () {
         rb2d = GetComponent<Rigidbody2D> ();
         jointRef = GetComponent<HingeJoint2D> ();
         motorRef = jointRef.motor;
     }
     
     // Update is called once per frame
     void Update () {
         if (Input.GetKeyDown ("left"))
             motorRef.motorSpeed = speed;
     }
 
     void FixedUpdate ()
     {
         
         
     }
 }