The throttle is loose by default for more safety during transport. Have a look at this video:
https://drive.google.com/file/d/11E-aSoRIKEVt6-k3VMQqDZY_ufrkU0DF/view?usp=sharing
If you do not have the screw, let us know. We can send you a new one. Alternatively, you can pick one up at any hardware store. It is a 5mm screw like this.