Sue Taylor at FDTS did show me how the belt is fixed to the reel. To increase the spring tension - pull the belt out as far as you can - put a small screwdriver through the slot in the reel spindle to stop it rotating and unwinding the spring - push the belt into the slot in the spindle on the reel so it comes out the other side and pull out the pin from the belt and then pull the belt back and out from the spindle - wind the spindle round to increase spring tension, being careful as you pull the screwdriver out in order to rotate the spindle so the spindle doesn't spin round and unwind the spring, put the screwdriver back in to lock the spindle - then push the belt back through the slot - put the pin through the belt - pull the belt out to take up slack and then pull out the screwdriver to allow the belt to wind back into the inertia reel assembly. It is fairly obvious once you start the job
