900S rear brake caliper piston issue - HELP!

[92 Blue 900S]

I dismantled the rear brake caliper and the piston essentially fell out when I removed the pads. I am trying to put it back together but do not know which way to orient the guts that go within the piston. It seem that this device should press down into the piston and lock into place but it will not. When I do instert it and put everything back together, the piston will not completely retract into the housing to allow room for the pads to fit over the brakes.

[900t]

you may need to remove the 14mm plug on the back and turn the little slotted shaft with a 4mm allen key to allow it to retract

[92 Blue 900S]

Thanks - I have completely removed the piston from the caliper and can see what turning the mechanism in the back of the caliper does - I should probably post pictures for all to see. it turns a leadscrew that engages threaded nut inside piston and moves the piston position in an out. the "nut" actually allows the piston move slightly along the axis of the leadscrew. http://www.flickr.com/photos/51894841@N00/3940002822/