the "high speed needle" is the one connected to the tank.. the other one in front is called the "air bleed" screw.. it acts kind of like a low speed needle..

that motor doesnt have a low needle.. it just has the high speed needle and the airbleed screw.. you need to start the motor and turn that needle untill you get the absolute max rpm then richen it.. counter clockwise maybe 3 or 4 clicks.... then hold the plane and have someone move the throttle to full open and when the motor comes up to speed.. point the nose up and down.. if it dies while pointing up... adjust the airbleed (on the front of the motor) by closing it (clockwise) just a tiny bit at a time.. repeat after every adjustment.. if it dies while pointing down.. adjust air bleed (open half of what you put in for pointing up) just takes patience and persistance... good luck