Kohler has gone to a yellow flush cannister gasket because the red ones failed prematurely. I change out that center post part as well when I repair a Kohler toilet of that kind. Home Depot carries a complete line of OEM Kohler toilet parts which is a good idea to stock as well as those for the American Standard cannister type toilet which I believe is the Champion.
Kohler toilets are notorious for the red gaskets failing, I have changed out many of the red seals with the yellow gaskets . Nice to see you back at it.
01:20 Ha, ha. I don't know why there are so many broken doorbells. Maybe you should go into the doorbell repair business. But, maybe nobody wants to spend money on a doorbell.
I always tell people to use the in the bowl style bowl cleaner that clips under the rim of the toilet if they insist on automatic toilet bowl cleaners. That way it doesn't contaminate the tank.