What I did may work for you?
I did pull the head on mine because the bolts were already loose, but while it was off, I would pour some gas/oil mix down the carbs (air filter assembly removed) while holding the throttle blades open so the mixture would go inside the motor, and then hit the starter button allowing the mix I had just poured in to fly all over the place (while the motor is turning over), which it did. I would put a towel over the open cylinders to try and catch as much as possible (trying to not make a big mess) I beleive I had a small amount of water in there. So by doing this it threw all the junk out that had been hydro-locking "my" motor. I can`t say what your issue might be, but don`t "jump" to far just yet. Also make sure your plug wires are as far away from this spray as possible, THE MIXTURE IS FLAMMABLE, AND COULD IGNITE from the spark plug wires, BE SAFE, BE CAREFUL. BE SURE of what you are doing! When you feel like all the junk is out, put the head back on, reinstall your plugs, see if it will fire.