i live in michigan also. laws are that it is a moped and you are supposed to get it registered. i have not done that yet but it is only $15.00 for a 3 year sticker. remember they do not put the size of the motor on the engines and their is no way to tell what size they are unless you pull the piston out. you have a 48 cc if you say more then 50cc it will be considered a motorcyle.
glad to have you with us. i personally do not think the police will bother you long as you are not out making trouble.