Ok you will have to undo the three(3) bolts holding the starter on the housing and remove it.
1. Then you will need to undo the shaft in the centre of the starter (use a spanner or shifter).
2. Then lift off the the plastic pulley and the spring is underneath it.
3. If spring is broken then replace it.
4. When fitting the starter back replace the 'O' ring.
We have more detailed information including pictures under parts list and manuals area.