if its a similar design to the 50 it'll be on the underside of the motor somewhere near where the centre stand bolts to the block The starter motor has to engage with the teeth on the variator to start the bike so its got to be around there
All the 2 strokes have them on the bottom but the 4 stroke piaggios have them on the top if memory serves me..Maybe due to the sump being on the bottom or something? But yeah its the only metal cylinder shaped thing on the engine it shouldnt take more than a minute or two to find tbh
just look around the whole engine their so easy to spot then either change the bushes in it or swap simple