So you've got power going round some of the wiring, are the handlebar switch gear internals OK? are they connected up? maybe you've missed a connection somewhere, are all the pins inside the multi-connector blocks clean & tight? the neutral indicator lamp wire is in the same multiple connector block as for the lights, that's not to say the others are in perfect condition.Just a case of looking more carefully. Wiring pics on google "aprilia rx50 wiring diagram" if that helps.
Chris P.Duck
March 2011