How to disconnect flapper on kohler k3386DA - Kohler K-3386-0 Rialto one-piece round-front toilet with seat and left-hand

Standard size is 2 inch

flapper sticking or worn remove and replace the following links show how to replace a flapper
Replace Toilet Flapper Yahoo Video Search Results Replace Toilet Flapper Yahoo Video Search Results

replace the flapper with a new one. There are universal flappers at your local home store that will work for you.

Water level in tank might be set too high, allowing water to drain out the overflow. lower the water level in the tank. (I am assuming the flapper is ok. Flapper may have a protective disc, which should be removed after installation.)

Sounds like the flapper is leaking water out of the tank. The flapper is the rubber valve that comes up and down every time you pull the flush lever. It is located in the tank at the bottom in the center. Very cheap part to replace.. Just turn the water off to the stool, take the top of the tank off, hold the flush lever down until all the water is out of the tank, reach in to the tank, disconnect the flush chain from the flapper, and disconnect the flapper arms holding to the stem. You can buy a flapper at any hardware store even at wal mart. Hope this helps.

Try cleaning the surface of the drain hole where the flapper fits. There might be crud causing it to not seal. Sometimes the flapper itself is not large enough (or too large) to properly fit the hole. If no good you might try weighting the flapper. Not easy to do. You'll have to pull the flapper, dry it completely find the right adhesive place the weight just right. And hope that works. Good Luck...

http://www.lockeplumbing.com/detail.asp?c=Toilet%20Parts&s=Kohler&s2=Float%20/%20Fill%20Valve&sku=KOH-1068030&r1=WHE-USS25C&r2=&r3=

See if your filler valve looks like the one in the picture from the link above.

Found your part: http://www.kohlerserviceparts.kohler.com/AccessoriesInformation.aspx?ServicePartID=f5a368efd5b74bcfae7fa0d0bb69bd39

These models need to have a flush valve flapper that has a styrofoam float on the lift chaninof the flapper. Go to hardware store or home improvement store and get a 'Korky brand toilet tank flapper with float 'ball". Cut the rubber ring piece away from the flapper and you don't need it (see cut here marks on flapper). Install flapper and adjust the float fairly close to the flapper.
When the water level drops in the tank and reaches the level of the float on the opne flapper, the flapper quickly closes causing the toilet to have a "surge" of siphon action which forces the water in the bowl to be drawn out.

New problem or old? Did you buy and replace flapper? Is the one you bought made for your model? Many of the Kohler brand flappers have floates attached to the chain about the flapper to help keep it open longer.