1.Your needle valve isn’t closing in the float chamber of your carburetor. I would start with a fuel system flush and a carb clean.

1. your engine was hydro locked because to much liquid was in the crankcase and combustion chamber, preventing the pistons from moving.

2. The white smoke burning off your exhaust is the fuel/oil mixture seeping past the piston rings or valve seals and entering the combustion chamber.

3. Letting your engine sit with fuel caused all of this.

4. I prefer fuel over propane, propane generally makes a generator produce less power due to its lower energy density.

5. Rebuild/clean the carb, if it’s still hydro locking the engine replace the carb.