Controlling multiple motors via PWM

Arduino code

void setup()
{
Serial.begin(9600);
}

void loop()
{

if (Serial.available() > 4)
{

int Motor1= Serial.read();
analogWrite (3, Motor1);

int Motor2 = Serial.read();
analogWrite (5, Motor2);

int Motor3 = Serial.read();
analogWrite (6, Motor3);

int Motor4 = Serial.read();
analogWrite (9,Motor4);

Serial.flush();
Serial.print(255, BYTE);
}

}