When adjusting a pulley make sure you have the proper amount of shims installed in the complete assembly. It is a good idea to start with too many shims so when the two halves are tightened together the belt is loose. To tighten the belt, remove shims from between the pulley halves one at a time re tightening the pulley halves each time to check tension. Proper tension should be about a half inch of deflection. Warning: if you tighten the pulley halves against the belt and not the shims you will break the inside half of the pulley . Store the leftover shim washers between the pulley outer half and the hat-shaped special washer.