As seen in the video, lift brushes' wires: this helps the brush moving flawlessly in the brusholder.

This operation is very important: if you forget to do this the wire may clamp in the o-ring sealing and prevent the brush from moving towards the electrical rotary joint. Waterproofness is also compromised, if this happens.

Come back here if you assembled everythinng but the motor won't turn on after applying power.