No, fuel shouldn't leak out! You have it waaaay to open if it's to the point where fuel is leaking out. Best thing is to do some research and find out where the starting point should be, this varies on different engines, can be anywhere from 1.5 turns out to 3.5 or more turns out. As Sdavied suggested, if you can't find out, 1.5 to 2 turns out would be a good starting point. So turn that screw all the way back in until it stops but don't force it. Then loosen it roughly 2 turns and start from there, if you're not familiar with nitro engines, it may be a good idea to get some help, on a heli, tuning mistakes can lead to big $ damage. Basically start the motor and if you're getting a lean or high winding type of sound, loosen the screwin 1/8 turns until you get where you want, if it's kind of a gurgling sound with possibly fuel spitting out of the exhause, youre too rich so close the screw 1/8 turn at a time. You basically want it on the rich side with lots of smoke, I would run it at as rich as possible with no gurgling and reliable running, this will give you longer engine life, cooler running engine and less chance of flame outs.