Not trying to rain on your parade but what you have is a 2 cycle lawnmower motor. It is air cooled (no water pump) and hard to get parts for. However the tune-up can be done in any lawnmower shop. They were sold under many store-brand names ie. mongomery Ward, Sears, JC Penny's ect.
If it runs - great. If it don't - don't put any money in it. Scrap it. Sorry, but you asked.