Invoke doesn't work when with certain second

I am trying to create an effect like this: - When zomebie touch a note, he speed up for 3 second then return to normal speed. The structure is this: - Zombie touch note, set bool isSpeedUp to true - Call speedup function - Increase speed in SpeedUp function - Invoke SpeedDown after 3 second - Decrease speed in SpeedDown - Set isSpeedUp to false

My problem is when I use invoke, 0.5s works fine (I can see the log that it call all functions and change variables properly) but with 1 second it does not call to SpeedDown function. I am desperate. I am new, so any help would be appreciated.

P/S: I tried waittoseconds but it doesn't work. I would prefer Invoke to work because it's cleaner.

using UnityEngine; using System.Collections;

 public class NoteController : MonoBehaviour
 {
      private bool isSpeedUp = false;
     private float timeSpeedUp = 5f;
         public float defaultTimeSpeedUp = 5f;
         private float DefaultMoveSpeed;
         private float DefaultTurnSpeed;
         private float starttimer = 0f;
     

        public void ZombieTouch ()
     {
         Transform goldnote = transform.GetChild (0);
         goldnote.collider2D.enabled = false;
         goldnote.GetComponent<Animator> ().SetBool ("CollectNote", true);
         isSpeedUp = true;
         DefaultMoveSpeed = Common.ZombiemoveSpeed;
         DefaultTurnSpeed = Common.ZombieturnSpeed;
         Debug.Log ("Zombie Speed -1 " + Common.ZombiemoveSpeed);            
         SpeedUp2 ();
     }
 
     void Start ()
     {
        }
        void SpeedUp2 ()
     {
     Debug.Log ("Zombie Speed0 " + Common.ZombiemoveSpeed);            
         Common.ZombiemoveSpeed = DefaultMoveSpeed + 2;
         Common.ZombieturnSpeed = DefaultTurnSpeed + 2;
         Debug.Log ("Zombie Speed1 " + Common.ZombiemoveSpeed);    
         Invoke ("SpeedDown", timeSpeedUp);
         Debug.Log ("Invoke striked");
     }        
     void SpeedDown ()
     {    
         Debug.Log ("Speed down called");
         Common.ZombiemoveSpeed = Common.defaultMoveSpeed;
         Common.ZombieturnSpeed = Common.defaultTurnSpeed;
         Debug.Log ("Zombie Speed2 " + Common.ZombiemoveSpeed);
         isSpeedUp = false;
     }
   void Update ()
     {
     }

}