There is a special bar that slots in the base and levers the belt down onto the motor shaft. Without it the job is hard to say the least. One way is to use a length of mains cable slotted between drum and belt and pull downward but it might take 2 people and works best with machine on its side. Also the right hand side panel and lid have to be removed which makes the unit very flexible. Good luck.
Ex BMW Mechanic., May 2008