Replaced the flush valve assembly in a Kohler Wellworth toilet. The existing valve was sticking and causing the toilet to run constantly. Turned off the water supply, drained the tank, and removed the old valve using a flush valve socket wrench. Installed a new Fluidmaster 504 valve along with a fresh tank-to-bowl gasket. After reassembly and restoring the water supply, the toilet now flushes properly with no running issues.