Highline toilet float valve comes up only so far and stops, but water keeps running.

if no float valve lever then its on the water valve itself usually a doughnut shaped that wraps around the valve /flushometer

Yes it could be valve just cause you changed the flapper doesnt mean that you stop water from filling in tank the valve that shuts water of can still be running the water will go down the bowl fill tube that is were the black tube goes that connects to the top of white pipe the simple whey to find out is just push down on black float and water will stop add in tank let off black ball and water should stop or just lift up on float arm and water should stop bend float arm if necessary.

You need to change the valve. It probably is stopped up with calcuim, etc.

You cannot adjust the pressure on the toilet. But you can adjust the stop setting screw at the top of the float arm. If the water is coming in too fast you can adjust the valve where the toilet water line connects to the wall water supply. Closing the valve a little will slow down the flow of water and it will take a little longer to refill the toilet water tank.

If the water keeps running, where is it going?
If it is going into the overflow tube, lower the water level setting.
Gary

The Kohler Cimarron is one of the most popular and reliable toilets out there. (My Favorite). However, depending on the hardness of the water and if you use cleaner tabs in the tank, these factors can lead to a malfunction.
The first thing you should do is hold the flapper (rubber seal inside the tank that releases the water down to the bowl) down with your hands for a few seconds after a flush and see if the toilet stops running. Sometimes the flapper doesn't seal properly therefore the fill valve keeps working non stop. Stopping the fill while holding the flapper down will confirm that your flapper needs to be changed.
If this doesn't work then try this....
The other common problem with a running toilet is with the fill valve itself. There is an attached float on the fill valve that goes up and down depending on the water level. Once the water level rises, it rises the float, and the float tells the fill valve to stop filling the tank. While the toilet is running (hissing), try raising the float all the way up with your hand and see if it stops. If it stops but not consistently with every attempt, then you will need to change the fill valve. I believe the Fluidmaster 400A is the replacement model.

Did you try to lubricate with something waterproof to stop the squeak? How about grease? Petroleum jelly, something. Or how about a weight on the high side to balance it out as it goes up. A lead sinker or a penny. Hope this helps.

The screw can be used but only for minor adjustments. The missing tube should be replaced. If this doesn't solve the problem purchase a repair kit. The repair kit comes with everything you need for about $20 and can be installed yourself (saving $$$ if you called a plumber)

You need to either bend the arm that connects tot he float down (if it is the type with the ball float) or adjust the height of the fill valve assembly. THis accomplished by slightly twisting the valve assembly carefully and sliding down a half of an inch or so and then twisting back to lock it in place.

This should fix you up right.

I have a Kohler toilet and Ingenium fill valve 85297-AA. My toilet kept running, the fill valve black cylinder wouldn't pop up and when I added blue food coloring to the tank, the blue color seeped through to the toilet bowl. First I replaced the flapper and that allowed the fill valve piece on the cylinder to pop up correctly and blue dye no longer seeped through to the bowl. I still heard a hissing sound when the toilet tank had filled and no water was going into the overflow tube. I called the tech support number on the Kohler website 1-800-4KOHLER (1-800-456-4537) . Here's what solved the problem: Turn off the water to the toilet.Take off the white cap of the fill valve by pushing it down and turning it counterclockwise as you would open up a childproof pill container. Then unhook the metal hook. Hold a cup upside down (I used a strong plastic cup) over the part of the fill valve that is left in the tank and turn on the water. (You need the cup because otherwise the water will squirt up to the ceiling.) The water will flush out the fill valve. Replace the cap and the hook and flush.