If you had the carb apart, check to be sure that the slide is in the right orientation, because it can be put in backwards, and then it won't drop all the way down to the seat, and cause high idle speed.
Also, check that the cable isn't hanging up from the bend at the top of the carb.
With the bike off, you should be able to hear a click, and see that the slide is all the way down when you let go of the throttle.
And yes, if that isn't the problem, you can try very small increments of retarding the ignition timing to bring the idle down.