The blower belt adjustment should be done with the motor cold, and have 3/4" deflection in or out on the long side of the belt. This should give you 1 1/2" total deflection. Once the motor is warm this will decrease to roughly 1/4" deflection in or out, or a total deflection of 1/2". Over thightening the belt can cause severe damange to the blower and/or crankshaft.
