The 46 is suppose to be tight at top dead center. It's the way an ABC engine is made. It's not a problem.

I'm not familiar with the 50 but it sounds like the thrust washer is engaged with a cone. Attach a fan unit or a prop and you'll be able to turn the engine over.

To remove the cylinder, slide the edge of a glow plug washer just into the exhaust port, from the inside of the cylinder. Turn the crank and the cylinder will be pushed out.

Before you remove the connecting rod, be sure to mark it so that you put it back the same way. Mark the piston as well.

For an unringed engine, you'll have to replace the cylinder and the piston.

Be careful.