with the back off, there is one lare bolt visible holding the motor in place, try loosenning this bolt it allows the motor to swing downwards tightening the belt. If with this bolt loose the motor will still not swing, if you look you will see the motor has an arm that goes off to the right and attaches to the main structure, feel behind the structure and there is another bolt loosen this and try swinging the motor down now.
JP, April 2005