Arduino wont change frequency

As bellow im trying to set my TCCR0B to allow the 4kHz frequency mode

but it seems to be stuck on the 490Hz default.

int TriggerPinFWD = 9;// MOSFETS on pin 9
int TriggerPinRVS = 10; // MOSFETS on pin 10
int analogPin = 3;   // potentiometer connected to analog pin 3
const int buttonPinFWD= 6; //button in for fwd motion
const int buttonPinRVS= 5; // button in for backwards motion

int LEDPin = 7; //Output for led pin

void setup()
{
  //First clear all three prescaler bits:
int prescalerVal = 0x07; //create a variable called prescalerVal and set it equal to the binary                                                       number "00000111"
TCCR0B &= ~prescalerVal; //AND the value in TCCR0B with binary number "11111000"

//Now set the appropriate prescaler bits:
int prescalerVall = 2; //set prescalerVal equal to binary number "00000010"
TCCR0B |= prescalerVall; //OR the value in TCCR0B with binary number "00000010"
  
  pinMode(TriggerPinFWD, OUTPUT);  // Setting the IO
  pinMode(TriggerPinRVS, OUTPUT);
  pinMode(LEDPin, OUTPUT);
  pinMode(buttonPinFWD, INPUT);
  pinMode(buttonPinRVS, INPUT); 
  pinMode(analogPin, INPUT); 


  
}

void loop()
{
 int val = analogRead(analogPin);   // read the input pin for PWM
 int val2 = digitalRead(buttonPinFWD); //read button switch 1 state
 int val3 = digitalRead(buttonPinRVS); //read button switch 2 state
  
  if (val2 == HIGH)
  {
  analogWrite(TriggerPinFWD, val / 4);  //write a value to Pin 9 if the switch 1 is on
  }
    else
    {
  analogWrite(TriggerPinFWD, 0);
  }
  if (val3 == HIGH)
    {
    analogWrite(TriggerPinRVS, val / 4); //write a value to Pin 10 if the switch 2 is on
    }
  else
   {
      analogWrite(TriggerPinRVS, 0);
  
  }
  if (val3 == HIGH || val2 == HIGH)
  {
    digitalWrite(LEDPin, LOW);  //Light standby led
  }
  else
  {
   digitalWrite(LEDPin, HIGH);  //Light standby led 
  }
}

pins 9 and 10 are controlled by timer 1 not timer 0, so you need to change TCCR1B not TCCR0B.