Coroutines and if statements

I have t$$anonymous$$s code here:

 void speed()
     {
         //Debug.Log (LeftRightMovement.speed);
         if(GUICounters.speed == 1)
         {
             //Debug.Log (LeftRightMovement.speed);
             LeftRightMovement.speed = 60;
 
             StartCoroutine(timer ());
             //Debug.Log (LeftRightMovement.speed);
         }
     }
 
     IEnumerator timer()
     {
         Debug.Log (LeftRightMovement.speed);
         yield return new WaitForSeconds(5);
         LeftRightMovement.speed = 30;
     }

My players speed is currently 30, when LeftRightMovement.score reaches a certain point I would like to increase the speed to 60 for 5 seconds using the coroutine and then set the speed back to 30 but as it is the speed is constantly at 60.

I also tried wrapping it in a boolean as i t$$anonymous$$nk its because it runs every frame and my score is always at 1. T$$anonymous$$s is what i tried:

 void speed()
     {
         if(ranOnce = false)
         {
             //Debug.Log (LeftRightMovement.speed);
             if(GUICounters.speed == 1)
             {
                 //Debug.Log (LeftRightMovement.speed);
                 LeftRightMovement.speed = 60;
 
                 StartCoroutine(timer ());
                 //Debug.Log (LeftRightMovement.speed);
             }
             ranOnce = true;
         }
 
     }

But i had no luck with that either, not$$anonymous$$ng comes out form the Debug.Log() then.

If anyone could point me in the right direction, that'd be great