here's how you tear into your Beancan from the top without driving out bottom pin, which is usually really tight.
remove top plate and bearing support. then remove large clip underneath.
remove side cap and disconnect advance springs.
remove two circlips, then remove three side screws. when everything is free. remove entire rotor/halls module as one assembly.
remove plastic plug that fastens wiring
if you don't disconnect springs first. springs will let go but might get stretched.
don't even think about removing thin rotor without a puller. the el cheapo battery terminal puller works perfect. take extra care not to loose tiny locator pin.
this is what you see after rotor is removed
early style has two screws, later has two rivets. someone has been here before me
drill out rivets and attach new Halls module taking care to splice/solder/shrink wrap wires to same length.
reassembly is NOT the same as removal. remove last circlip, separate center shaft from halls plate. service advance weight sparingly with a light high quality oil. then insert center shaft, then attach both springs while you have easy access to springs. otherwise it's almost impossible to reattach springs from tiny side cover hole.
next insert hall module plate, carefully aligning up with three screw holes. this pic is shown with old sensor.
replace rotor and carefully drive locator pin with a pin punch.
replace both circlips
install top large circlip and outer cap ... use a tiny dab of grease when installing top bearing plate.