Dyson DC04 Absolute?

How do I remove the drive belt cover inside the machine, I have had a chew on to get inside but It was getting late and dark and starting to lose it so job for tomorrow. Cannot split motor/filter casings. Do I need to strip the adjustble switch control to remove the belt cover ?

just that its lost its pick up, and has an itermintent whine/clicking when shutting slowing down. Both belts seem ok but reading other posts there is a clutch in there too ??
Suction pipes are clear and plenty of ummph but put your hand across sole base plate and its not very strong, are the brushes worn on the brush bar, and is there a tolerance for the length of bristle before needed replacement.

tried to follow a link on previous post but failed

I know you can clean the top filter with water, but what about the bottom filter, its black and it states lifetime but surely this must restrict the suction to the motor,

Thanks in advance