Wow.. Not good. Not having that screw there will allow fresh air into your motor causing a lean condition. This will burn your motor up in no time. Also, you will not have a good way to set engine idle as well. Make sure you get the correct screw with spring for that right away. If you have to run the motor, make sure to cover or seal the hole until you can get the correct screw for it. You do not want to burn your motor up. Enjoy the ride.