This is the holy grail of the service manual. For the Liberty’s LEADER or i-get engine family, you get:
Using the correct fluids is vital. The Piaggio Liberty 125 Workshop Manual specifies the following for standard 125-200cc Euro 3 models: Piaggio Liberty 125 - 200 Euro 3 (EN) | PDF - Scribd Piaggio Liberty Service Manual
piaggio-liberty-service-manual-guide
Replace the spark plug (specifically models using Champion RGN2C or similar). This is the holy grail of the service manual
Always ensure you have the correct manual for your specific model year and engine size. When in doubt, consult a certified mechanic for safety-critical repairs like brakes and steering head bearings. Piaggio Liberty Service Manual