The plastic pulley use to be replaceable, however they no longer make a replacement pulley, you will need to replace the entire motor on the unit, as for motor adjustment, there is none, it uses slide plates under the motor to set the tension as the water goes out in the spin cycle, it slides back and forth on a plate. The part number for the motor is 21001950, You can order the parts you need from the following places, http://www.apwagner.com/, http://www.repairclinic.com/, or http://www.partstore.com/, all of these places offer easy returns and reasonable prices for their items.
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The motor is easy to access, yo will need to pop the top, you can do this with a putty knife where the front meets the top about 1 inch from each side push in the putty knife to release the clips there, then you will see 2 screws that need to remove to take off the complete front of the machine..