Is the spark plug wet or dry?
You may have a clogged jet, which would make the plug dry, or a stuck float in the fuel bowl, which would flood and you'd smell fuel.
The diaphragm in the top of the carb may be torn also.
If there's fuel going to the carb, it's not getting in the engine if the jets are blocked by residue or debris.
it still sounds like a vacuum problem especially if some hoses aren't correctly attached, or the petcock may be faulty.
We're still talking carb problems, but you'll have to check the connecting wires to the coil and plug, they must be firmly attached at every union.