Take out the spark plug and see if you can turn the flywheel by hand. If gas runs out of the spark plug hole, then the carb is leaking and is creating a hydrolock situation. Do not crank the engine to expel the gas from the cylinder. Use compressed air, or just let it evaporate. Spraying gas creates static electricity that can ignite the gas fumes.
If you can't turn engine, then either the engine is siezed or something in the drive train is keeping the engine from turning.
