they have a variable adjustment pulley, so in other wors it has a strong internal spring on the inside of the pulley that tensions the belt,
to remove it, see the pully roughly in the middle and towards the passengers side of the motor, it was a hole where you can place a 3/8 or 1/2 inch bar, insert one the and push in the direction so the belts get slack, then just slip it off,
make sure you draw up a mud map of the belt direction