18hp Craftsman Lawn Tractor Starting problems

I am have an issue with my tractor. It won't turn over. The only way I can actually start the tractor is to take the spark plug out, and then it will start after shooting out some fuel. Once started it runs fine. We have removed and cleaned the carborator, replaced the spark plug, replaced the starter plug and it has a new air filter. Can anyone advise what needs to be replaced? Thank you.

You may have cleaned the carb, but the needle valve is still leaking fuel into the cylinder. Be advised that cranking an engine over and spraying out the fuel can cause static electricity lighting the fuel.