KX 65 screaming revs

Make sure throttle tube rotates easily. Then check for binding in the cable. Then what happens most that ive seen is the spring gets bound in the slide and it holds it up. Just make sure its together correctly and operates correctly when you put it together

Not sure about your bike specifically but sometimes its easy to put them in 180 degrees off if youre not paying attention.

Make sure the needle is going into the jet or it will hang up. Also remember that the slide can only go in one way or it will hang up as well.

Paw Paw

The orientation of the plate is a little confusing, make sure you didnt put the end of the cable through the little hole (B in your picture) first. It seems like it should go through there first before connecting to the slide but it doesn't

Lets see a picture of what you have done.

Check the throttle cable adjustment on the throttle itself. This happened to me a few weeks ago on our husky 85. Cable wasn’t properly adjusted from factory

Take the carburetor out of the manifolds and leave the cable connected. Can you see through the carb throat to the other side? You should not be able to, except for perhaps a little slice of daylight at most. The slide should come down and close off the airway almost completely.
Now turn the throttle. Can you see the slide moving up? When you let go of the throttle does the slide snap back down? These are all the things it should be doing.

There is a guide pin on the inside of the carb body which slots into the groove in your slide; be sure those two pieces mate well and aren't gunked up with anything.