Video by Vespa Motorsport via YouTube
Source
Diagnosing Battery Charging issues on a Vespa LX150 or ET4
Parts that will fit 2001-2009 ET4 150 or LX150
486062 Voltage Regulator: https://www.scooterwest.com/regulator-et4-lx150-gt200-bv200-486062.html
82572R Replacement Stator with better upgraded Flywheel: https://www.scooterwest.com/flywheel-and-magneto-82572r.html
828135 Stator: https://www.scooterwest.com/stator-plate-et4-lx150-828135.html
436783 One time use Lock Nut for Flywheel: https://www.scooterwest.com/variator-nut-for-new-vespa-125-200-436783.html
TOOLFLY Flywheel Puller: https://www.scooterwest.com/tool-fly-wheel-puller-vespa-piaggio-toolfly.html