Once you open the valve cover, check the clearance. There should be a TINY bit of play between the rocker arm and the valve.

Once you have checked that, rotate the prop and make sure that the valves are moving properly (Not stuck or sticking)

Then, unplug the tank altogether. Prime the carb and try it. You should get at least a few pops if not a short run. Then you at least know that you're getting combustion.

Now hook up the tank and go from there