cristian seminario

hi guys i'm new here i'm looking to upgrade my dragstar to 180cc but i don't know if i have to change the cylinders heads or just keep the stock ones i'm asking this because in every upgrade kit i seen online there isn't new cylinders heads and i can't find anything about this online has someone ever done this upgrade before? this is my dragstar please don't hate i know there is nothing more ironic than a japanese bike whit american flag livery