These carburetors are basically similar in design. The 4160 is an end-inlet carburetor, while the 4150 carburetor has been both an end and center inlet design.
The early model 4150 uses a bimetallic choke mounted on the carburetor. It is correctly set when the cover scribe mark aligns with the specified notch mark. The later model 4150 and 4160 employ a remotely located choke. To adjust, disconnect the choke rod at the choke lever and secure the choke lever shut. Bend the rod so that when the rod is depressed to the contact stop, the top is even with the bottom of the hole in the choke lever.Float Level
Position the vehicle on a flat, level surface and start the engine. Remove the sight plugs and check to see that the fuel level reaches the bottom threads of the sight plug port. A plus or minus tolerance of 1 / 32 " is acceptable. To change the level, loosen the fuel inlet needle locking screw and adjust the nut. Turning it clockwise lowers the fuel level and counterclockwise raises it. Turn the nut 1 / 6 of a turn for each 1 / 16 " desired change. Open the primary throttle slightly to assure a stabilized adjusting condition on the secondaries. There is no required float drop adjustment.Fast Idle
Open the throttle and place the choke plate fast idle lever against the top step of the fast idle cam. Bend the fast idle lever to obtain the specified throttle plate opening.Choke Unloader
Adjustment should be make with the engine not running. Fully open and secure the throttle plate. Force the choke valve toward a closed position, so that contact is made with the unloader tang. Bend the choke rod to gain the specified clearance between the main body and the lower edge of the choke valve.Accelerator Pump
With the engine off, block the throttle open and push the pump lever down, Clearance between the pump lever arm and the spring adjusting nut should be 0.015" minimum. Turn the screw or nut to adjust this clearance.Secondary Throttle Valve
Close the throttle plates, and then turn the adjustment screw until it contacts the throttle lever. Advance the screw 1 / 2 turn more.Air Vent Valve
Close the throttle valves and open the choke valve so that the throttle arm is free of the idle screw. Bend the air vent valve rod to obtain the specified clearance between the choke valve and seat. Advance the idle speed screw until it touches the throttle lever, and then advance it 1 1 / 2 turns.Vacuum Break
Secure the choke valve closed and the vacuum break against the stop. Bend the vacuum break link to gain the specified clearance between the main body and the lower edge of the choke valve.