79 HONDA CM400T: K&L Air Cut-Off Valve Set Alternative to the costly O.E.M. assembly. To prevent "afterburn" generated by a lean fuel mixture when closing the throttle, the cutoff valve temporarily closes the slow-jet air passage, creating an instantly richer mixture. Included in these high quality kits are all parts necessary for a complete rebuild (diaphram, spring and O-ring). Sold as a kit.