Auto, you remember that tube that came out the top of the carb when you took it apart? The one that is connected to the throttle cable? The gold colored metal tube that lifts up and down when you twist the throttle?
Well, that diddnt go back in right. Either you are missing a spring, or it is in sideways. If you are missing a spring, then yourthrottle grip will have no tension, in other words, it will just be loose.
That tube must be pointing in the right direction when it goes back intot he carb. There is a little notch running up the side of it. That must match up with the little bump that sticks out in the hole it goes in. If it dosnt match up, the slide will only go halfway in, and get stuck. You will still be able to screw the top of the carb on, but it wont work.
This should be easy to fix. You dont even have to take the carb off. Just unscrew the top part of the carb. the part where the throttle cable goes in. You should be able to pull out the slide tube. It has a needle at the end. Now notice that on that tube there is a notch running the entire length of it.
Now look down into the hold it goes into, or feel in there with a clean finger. you will see or feel a little bump that sticks out. That is suposed to line up with the notch on the slide tube. It fits inside the notch, and the tube is kept straight with that bump.
Also note that the needle at the end has to fit into its hole in the bottom of the carb. Usually slides right in, but sometimes it needs to be wiggled.
Now make sure that slide tube goes all teh way down, and screw that cap back on.
Now if you take off the air filter, and look into the carb, you should be able to see that slide, and it should be blocking the passageway. If you twist the throttle, it should raise that slide up.
NOTE: The only thing that your idle screww does is raise and lower that slide tube about 1mm. Thats how you adjust the idle. The higher it sits, then the more air gets through and the faster it runs. the lower it is(idle screw screwed out), the lower the slide sits, and the slower it runs as less air gets through.
LEt me know if you need any more help.