For a few weeks our toilet would sometimes sing or squeal in a high-pitched tone. My wife urged me to call a plumber, but I valiantly searched YouTube for a video on how to fix it myself. I found lots of videos with the same problem, including the same brand of toilet (Kohler). I looked at the first two, but they described how to replace the mechanism inside, which looked like more than I wanted to undertake, since I’m all thumbs with that sort of thing. But I kept reading descriptions. They all seemed to require the same thing and talked about where to get the kits, etc. In position six or so I came across this one:

It claimed that you can fix it yourself in five minutes with nothing more than a plastic cup. I followed it, and sure enough, it worked and in less than three minutes it was fixed. This is the official Kohler video. The point is, don’t trust all those how-to videos on YouTube. You have to search carefully and determine which, if any is reliable.