Abstract: A tool for mounting a spring retainer plate on a valve stem with a locking member includes a tool shaft having a socket on one end thereof for cooperation with a spring retainer plate to push same over a valve stem. A yieldable pin extends outwardly of the shaft at its one end centrally of the socket for engaging an end of a valve stem. An abutment surface generally radially outwardly of the pin engages a locking member to move same axially over the end of a valve stem in following relationship to the spring retainer plate for cooperably locking onto the valve stem to hold the plate against displacement from the stem.