Timer1 CTC mode not resetting count

I’m trying to drive stepper motors using interrupts but I’m having trouble getting the interrupt configured correctly.

Here is my initialization code for the interrupt

void timer1_init()
    // set up timer with prescaler = 8 and CTC mode
    TCCR1B |= (1 << WGM12)|(0 << CS12)|(1 << CS11)|(0 << CS10);
    // initialize counter
    TCNT1 = 0;
    // initialize compare value
    OCR1A = 100;
    // enable compare interrupt
    TIMSK1 |= (1 << OCIE1A);
    // enable global interrupts

Here is my ISR

    SET(MOTOR_PORT,LEFT_MOTOR_STEP); //set the pin high
    delayMicroseconds(3); //keep high for a bit

No matter what i set OCR1A to it always steps at the same speed.

It isn’t resetting TCNT1 like It should (if i’m reading the datasheet correctly).
I verified this by printing TCNT1 in the loop code and I am seeing values greater than 100.
Is my understanding of CTC mode incorrect or did i just miss something that i need to set?