What is this Gasket in the toilet tank and how to replace

[Jjbrock7]

I found my toilet running so I looked inside the tank and found this incredibly loose gasket caught in the flapper holding it open. It looks like it has come off the gasket between the tank and bowl maybe due to over tightening. I can't seem to find anything online that directly relates to this so I am a bit at a loss

I have attached some pictures any help is appreciated. Does it need to be replaced, how is it replaced and is it simple enough to do or should I call a plumber.

 

[Twowaxhack]

That’s part of the gasket that seals the flushvalve ( black plastic ) to the tank.

It may never leak, but it might.

Thanks Kohler

 

[TomFOhio]

Who ever tightened that in sure did over do it. It looks like you could peal that extra gasket away. The good part is still
under the flush valve. Any sign of water between that tank and the bowl you will then have to replace it. You take the bolts
loose and the tank will lift off then you can replace the flush valve. Depends on your skill level whether you do it or a plumber.

 

[Twowaxhack]

Kohler is famous for over tightening everything.

I had to use a 1/2” socket and small breaker bar just to remove a Roman tub faucet ceramic cartridge.

 

[Jjbrock7]

Well glad I somewhat diagnosed it. Not currently showing any signs of leak, but may look to replace in the near future.

 

[sarg]

If it's not leaking .... just snip off the shown excess so it does not interfere with the flapper closing.