With the spring removed from that barrel type carb, it will not work correclty anymore. The way they are built, the spring is needed. You will need a new carb.

If you use some good locktite or JB weld on the threads of the prop hub, it will not come loose. When the engine fires and runs, it is the correct direction to keep it tight. Just starting can loosen it, but if you do like I said with the locktite or JB weld, it will stay on. Also you can drill a couple holes in the side of the hub and run set screws.