Out of curiosity ... I google this problem .... here is a manual for your scooter ..
http://www.motorscooterguide.net/Man...ice_Manual.pdf
On page 185 is a schematic for the charging system. I'd be checking the switch and the regulator/rectifier. You may have a bad diode in the regulator back feeding from the battery to the lights. Looks like the manual has good trouble shooting and how to test information. Good luck finding the problem and let us know what you find.