Engines don’t have serial numbers (except rotax) and the carb is usually made by someone else anyway. If you could post a picture… it’s probably a Tillotson HL kit you’re after. Look on the mounting flange of the carb for numbers.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience