If I sell my supercharger kit, or buy a used one, does the new owner have a warranty?

The new owner has warranty only on the Rotrex unit so long as it is no older than three years from the original date of assembly/manufacture via Rotrex. The rest of the components only offer a 1-year warranty to the original owner with verified proof of purchase. There are no components covered under a used kit other than the head as long as it is within three years from the original date of manufacture