I recently purchased a HS720 AS snow thrower and while the instructions for getting the product up and running I was unable to locate the engine serial number based upon the directions listed in the owners manual. Without this number I was unable to register the product with the manufacturer. I did get the snow thrower started on the first attempt which is why a purchased another Honda product. This one appears to be as reliable as the previous model I had that lasted 25 years until it was stolen. The purchase was made at one of our local Home Depots.