I came across a Honda manual on carburetors from a factory school I took a few (dozen) years ago. I think the information has held up pretty well over time and scanned it in so others could read it.The manual covers all the basics for all types of carbs used in motorcycles. It has an especially good explanation of constant velocity carbs with floating pistons.
You can find it here (Caution: it is a big file and is slow to load. Patience is a virtue.)
One of the biggest problems with carbs, especially here in New England where they sit all winter, is getting gummed up with gas that has sat for too long. The newer "green" gasoline formulations are only making this worse. In my opinion, the best carb cleaner is made by Yamaha and is cleverly labeled "Carburetor Cleaner". Your local dealer has probably never even heard of it much less stocked it but it's in his parts accessories book under part number ACC-CARBC-LE-QT. Price the last time I bought it was $7.95 / qt. You mix it 1:3 with gas and pour it into the fuel line after draining the float bowls and let it sit for 1 hour (or overnight if it's real ugly). Works like magic and doesn't hurt the rubber parts!