Take the plug out crank the engine a few seconds then try with a fresh plug & no added fuel
If it goes bang then we are good to go
If not
With a fresh spark plug, try that again with 1/2 TEASPOON , no more of fuel down the plug hole
Too much fuel just floods the engine so the plug gets wet and inside the cylinder the spark will just run down the sides so no bang , in fact a 1/4 teaspoon would be more than enough .
If nothing else we have confirmed the exhaust valve is working so we are making progress