You can also Motorcycle Carburetor gently pry it with a screw driver (gently). If it doesn't want to budge don't force it.
Instead finish reading this article and pay attention to the boiling tips further down.
Now your carbs should be pretty well emptied out. If the throttle on the bike moved fluidly and smooth there is little reason to do much to the carb bodies themselves.
However, if the trottle was real sticky or frozen there are a few things you can do to free it up.
Sometimes just drenching all the throttle components on the carbs and letting it soak is enough, other times it is not.
I generally try to break racks of carbs apart. It isn't often necessary and can be confusing to put everything back together in the right places.
Also, the little rubber connector hoses and o-rings have a tendency to crack or leak if you mess with them.
If you can't work the throttle back and forth until its smooth have a look at the boiling tips further down.
Go too long between changes and your oil won't protect the metal parts from wear as Carburetor Seat effectively as it should.