Chris:

The pull starters on the little car engines are sensitive to the way you pull them.

One, don't yank it. Pull the handle up gently until you feel the engine load on it, then pull sharply.

Two, stop pulling before the cord is all the way out. If you pull the cord as far as it will go, and come hard against the stop, you will break it regularly.

Now, on your particular engine. If you are saying you cannot turn the engine at all by hand you have a problem in the engine. But if you are saying you cannot turn it all the way through one turn, this is normal for an ABC engine. If you can turn it through with the starter pull I doubt your engine is at fault.

I suspect that your problems will all be solved by changing the way you pull the cord.

Bill.