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The idle goes up when you take the choke off because that changes the mixture from way, way too rich to just somewhat too rich. The more correct the mixture is, the faster the idle. Warm up the engine fully, take the air cleaners off so you can see what you're doing, then do this:
Turn the nuts under the carbs CCW until the jets are all the way up. You can lift the pistons in the carb domes with your fingers to be able to see this happening. The pistons should be stiff to raise, and should drop down quickly under their own weight when released. If they're not stiff, you're out of oil in the dampers.
Turn the nuts CW 1-1/2 full turns (6 "flats").
With the choke all the way off, turn the idle speed screws CCW so the throttles close completely -- you can see the point where the mechanism stops moving -- and then CW 1/2 turn beyond the point where they start the throttles opening. Ensure that the fast idle screws on the choke mechanisms are not touching the cams they ride on (these are outboard of the carbs, lower down, with the heads facing the engine block). Make sure there's some slack in the throttle linkage.
Start the engine. Turn the idle speed screws equally until you have a sensible idle speed. Put your head down in front of the carbs and listen for the hiss to be equally loud in both carbs (if this is hard to tell, listen through a piece of hose to each carb individually). Use the idle speed screws to get the hiss as even as possible while maintaining a good idle speed.
Now adjust the mixture nuts under the carbs equally one flat at a time until you get the fastest idle speed -- could go either CW or CCW. Adjust idle speed with the upper screws as needed, keeping the hiss equal. Once you get all you can out of that, try adjusting the mixture on one carb at a time for a yet faster idle -- they don't always come out exactly the same number of flats down.
Now "blip" the throttle slightly by hand, pulling on the upper linkage where the rod connects down to the lower linkage. The pistons in both carbs should lift off exactly together -- they may not lift an exactly even amount, but you want them to start moving exactly together. This is adjusted by loosening one of the cranks on the lower linkage (that goes between the carbs), moving the crank a small bit, and retightening. Be patient and picky -- once you have it right, it'll stay that way for years.
Finally, pull the choke out slightly so the idle goes up slightly. The throttles are now being controlled by the fast idle screws instead of the upper idle speed screws. Balance the fast idle screws for equal hiss. Push the choke back in and ensure the idle drops back to where you adjusted it earlier.
That's it -- you're done.
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