Time.timeScale question

Why doesn't this code make it so time plays at 3x speed until I use horizontal input? It simply returns a 3x speed effect constantly. I've tried about 10 different combinations for this so far and I can only get it to work perfectly in reverse. IE time speeds up on horizontal and then returns to normal when input is null.

 using UnityEngine;
 using System.Collections;
 
 public class FastMo : MonoBehaviour {
 
     void start()
     {
         Time.timeScale = 3f;
     }
 
     void Update()
     {
         if (Input.GetButtonDown ("Horizontal")) 
         {
             if (Time.timeScale == 3f)
                 Time.timeScale = 1f;
         }
 
         else
         {
             Time.timeScale = 3f;}
         }
 }