If your Kohler toilet is running, it's doing more than wasting water--it's also running up a sky-high utility bill. Most of the time, a toilet is running because some of its component parts have misaligned slightly. All you have to do to stop the continuous flow of water is jiggle those parts--the float or the seal--back into place. Even if you have to replace the float assembly in the toilet, it's a simple operation that doesn't require specialized tools; just make sure you know where the valve is to shut off the water flow to the toilet--usually on the wall just behind the toilet.
Lift the cover off the toilet tank and set it aside.
Jiggle the black float inside the tank. Sometimes, that's all that is needed to stop the water from running through the tank if the float was originally stuck.
Reach into the tank and make sure the plug that seals the hole in the bottom of the tank is firmly seated. If it seals properly, the water will stop running through the toilet and fill the tank, lifting the float and stopping the inflow of water.
Clean any debris away from around the exit seal of the tank--the same plug you just checked--and see if that helps the plug to seat properly.
Replace the float assembly, if necessary, by unplugging the hose from the top of the float assembly, unscrewing the assembly and removing it from the tank, then screwing a new assembly in place. Then plug the plastic hosing back in to the new assembly.
Install a new seal at the bottom of the tank if necessary; shut off the flow of water to the toilet, pry the old seal off its pegs, and snap the new one into place.