Hello Michael,
Youi have to take the motor out which is an art form on it's own, there are two types of 708, one with a gear driven motor and one with an open motor for exports, take the top off your machine first to see which one you have, look at the balance wheel end to see if there is a gear that is driving the balance wheel, one you have the motor out you have to take it apart and you could come unstcuck, make sure you can get the motor brushes, if you want me to go into details from beginning to end e-mail me.
Ken
drivewithken@blueyonder.co.uk
May 2008