I wouldn't attempt adjustment until float/fuel level in the bowl is checked. There's a specific way to do this before the carbs are removed. (see manual) Hard, or impossible to do if the float is stuck.
Sometimes, careful but sharp whacks on the sides of the carb can free the float. Like a screwdriver handle and many quick raps to vibrate the carb.
Black smoke means excess fuel.
It will see excess pressure if the cylinder is filled with gas, but it has to have a blown gasket or cracked cylinder to push fuel into the coolant.
If it's getting coolant into the cylinder, you should see evidence of that on a spark plug. Looking steam cleaned or tiny water droplets on the plug.