After a lot of mileage, usually 20,000km and up, your big bore kit may lose a bit of compression and power. If its a Polini big bore kit from Scootling (P166.0105), replacing it with this new 46mm bore piston kit may do the trick to get your performance back.
Includes piston, pin, clips, rings. You should change gaskets at the same time, search MP2090387 on this online shop
This is to suit the Polini big bore kit for Yamaha/Minarelli with 12mm pin and CPI, CMG, Benelli and others with this style engine.
Sample image only