removed engine from bike today,brought this bike as non runner put some fuel in her and she ran,so i took off head piston is like new ? no carbon in eaxhaust ports strange,top of piston says .060 (1.52mm)wich i think means 3rd over bore correct me if wrong please,as i no nothing of bike, bore is good little corossion on top 15mm was looking to rebore and replace piston anyway,can i go 4th over bore and can you get piston this size,and what size piston would i need ? would it be a 85mm piston is there such a thing 
measured bore with vernier and it measures 83.34mm and the piston measures 82.70mm but that doesnt make sense as led to believe standard bore is 83.00mm

measured bore with vernier and it measures 83.34mm and the piston measures 82.70mm but that doesnt make sense as led to believe standard bore is 83.00mm