we had a similar problem and unwisely removed the screw revealed when the housing was removed from the engine. Don't attempt that !.
Take off the housing, remove any oddment of pull rope, carefully wind (anti-clockwise) the central spring assembly (you'll hear it clicking as you do so) several complete turns; holding the central section still, insert the rope through the outer casing and the hole on the central section and knot the end. Release central section slowly, allowing the rope to be pulled inwards. It may need further pretensioning in this way until the rope returns fully.
HR, June 2011
