Originally Posted by KRIS...
I had the clicking from new with my 120SR and I thinks its the screw head that attaches through the bottom of the main shaft.
It seems to have gone now as the screw head has shaved through the plastic.
Can you post a picture of it? Mine has a screw on top of the main gear through the gear collar and main shaft just below the lower shaft bearing, but there is about 1/32 clearance between the screw head and any plastic other than the sleeve of the main gear that it is holding in place.