Bowl does not fill to correct level - Kohler K-3489 Cimarron Comfort Height Elongated Toilet With Left-Hand Trip

The fill valve is easily adjusted to set the correct water level inside the tank. The following video will show how this is done.
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You move the float that rises up when the bowl fills down. You will need to play with the adjustment to see what level you want.

There should be a small black rubber tubing piece that connects to the fill valve and the other end goes in the overflow tube to refill the bowl after each flush. Make sure this tubing is installed correctly and that should solve the problem. Hope this helps.
Bob

My first guess would be the float bowl for the carburetor. The fuel level needs to be maintained at a specific height in the bowl. There's a float inside that activates a valve which allows fuel to fill the bowl - once the correct level is reached, the valve closes. On my old Virago there were simply two tangs inside as I recall that needed to be bent manually to make the adjustment. To check the level you would attach a piece of clear tubing to the drain port on the bottom of the bowl.....when the drain was opened the fuel would fill the tube to the same level as is in the bowl. You would need to find the correct spec for that level and adjust if necessary.

Make sure the fill tube in the tank from the fill valve is in the overflow tibe inside tank. The tube allows bowl to fill with water to correct level.

Check to be sure small tube is flowing inside the ovefow tube. This is the water that flushes the rim holes, and refills the bowl. If you don't have flow clean or replace the float valve.

The bowl is filled up with the little hose inside the tank, it locks inside of the overflow drain. And runs water in there as it flushes to swirl the water and fill the bowl. Water seeks it's own level, and the level in the bowl is at the top of the trap. It has to hold water, unless it isn't filling or it is leaking. Check out the filler and hope the bowl doesn't have a crack in it. Hope this helps.

First off,If the air vent was clogged the toilet would back up and overflow and when it did flush, it would make a gurgling sound.
secondly the water level in the bowl is not important as long as it covers the opening,The water is only there to keep out sewer gases so they don't enter your home and the shape of the trap will always maintain the proper amount of water needed to prevent this.
The previous water level may have been due to a partial clog that has since been removed.

If very little water is used on initial flush, The bowl is functioning as a tank for second thorough flush. The high water level cannot stay high in the bowl while in motion or you would have a mess ion start and stops.