You should have two needle valves. The one closest to the engine should be LOW.
The large chrome screw is (I hope) the throttle stop screw. As long as you are controlling the throttle with a servo you don't need this , just back it out so it cant stop the throttle or just remove it. Make sure it is the throttle stop screw before you do anything.

If you have a carb #." rcign " will tell you anything you need to know about it.