Finally getting to the float valves - good - although I can't figure why both would be stuck??
Blackdog....have you opened the drains and let a quart flow out of each carb. If you can get that much to flow quickly, your fuel flow is ok. If not fix the blockage between the float valves and the petcock as already been stated.
I wouldn't blow compressed air in the fuel inlet to the carbs unless the float valves were removed or unless you could keep the pressure very low. Make sure the drains are opened.
