How to fit a tune a 21mm carb

Hello there everyone this is my first time using a forum..I need help I have a piaggio zip 50cc 2t with a pm tuning 70cc bore kit,pollini veriator,lio Vince tt handmade exhaust, mollosi belt. I would like to put a 21mm carb on but don’t no were to start with tuning any help I’m not sure what jet is in current carb as I brought bike with most the set up on it excluding exhaust and belt please please help me???? Thank you

 

Start with A big main jet, check spark plug colour to see how it's running. adjust mixture screw to what it needs while ticking over.