E. ADJUST SECONDARY THROTTLE STOP SCREW - Back the secondary throttle stop screw out until the secondary throttle plates are closed in the bore. Turn the screw in until it touches the stop on the lever, then give it one half turn more.

Figure 33. Secondary Throttle Stop Screw Location

F. ADJUSTING THE IDLE - Seat the idle adjusting needle lightly and back off one full turn.

Figure 35. Adjusting Idle Air Screw

Figure 34. Adjusting Idle Fuel Mixture

Figure 36. Carburetor Adjustments

I. ADJUST AIR VENT ROD AND VALVE

G. ADJUST IDLE AIR SCREW - The model 4160 with mechanical secondarys has an idle air adjusting screw located in the main body. Turn this screw in until it seats lightly and back it off one full turn. After installation on the engine a reset ting may be made.

(1) Adjust air vent rod and valve by checking the clearance from valve to seat with a drill with throttles closed. This clearance should be taken between the valve and the seat and must be .050 to .070.

H. ADJUST IDLE SPEED SCREW - On all models except 4160 with mechanical secondarys, the idle speed screw must be tightened until the primary throttle plates are cracked slightly.

(2) Early production low inlet fuel bowl models have a different vent rod. The clearance of the air vent valve on these models is corrected by bending the end of the pump operating lever.