Intake and exhaust valves for Active mopeds. The valves open and close the ports in the head: the intake valve lets the mixture in, the exhaust valve lets the gases out.
Replace them if they are burned, no longer seal, compression is lost, or there is knocking. When replacing them, the seats are lapped and the clearances adjusted. If you are not sure of the cause of the fault, diagnose the assembly first so as not to replace anything unnecessarily.
