See Figure 1
This carburetor is used on the 4-121 engine.
ADJUSTMENTS - Float Level
- With the carburetor air horn inverted, and the float tang resting lightly on the inlet needle, insert the specified gauge between the air horn and the float.
- Bend the float tang is an adjustment is needed.
Fast Idle Cam
- Place the fast idle screw on the second step of the fast idle cam and against the shoulder of the high step.
- Place the specified drill or gauge on the down side of the choke plate.
- To adjust, bend the choke lever tang.
Choke Plate Pulldown (Vacuum Break)1977-79 MODELS
- Remove the three hex headed screws and ring which retain the choke cover.
- Push the diaphragm shaft against the stop. Push the coil lever clockwise.
- Insert the specified size gauge on the down side of the primary choke plate.
- Take the slack out of the linkage and turn the adjusting screw with a 5 / 32 in. Allen wrench.
- Attach a hand vacuum pump to the vacuum break diaphragm; apply vacuum and seat the diaphragm.
- Push the fast idle cam lever down to close the choke plate.
- Take any slack out of the linkage in the open choke position.
- Insert the specified gauge between the lower edge of the choke plate and the air horn wall.
- If the clearance is incorrect, turn the vacuum break adjusting screw, located in the break housing, to adjust.
Secondary Vacuum Break1977-78 MODELS
- Remove the three screws and the choke coil assembly.
- Place the cam follower on the highest step of the fast idle cam.
- Seat the diaphragm by applying an outside source of vacuum.
- Push the inside choke coil lever counterclockwise for 1977; clockwise for 1978, to close the choke valve.
- Place a gauge of the size specified in the chart between the lower edge of the choke valve and the air horn wall.
- Bend the vacuum break rod to adjust.
- Replace and adjust the choke.
- Position the throttle lever at the wide open position.
- Insert a gauge of the size specified in the chart between the lower edge of the choke valve and the air horn wall.
- Bend the unloader tang for adjustment.
Secondary Throttle Stop Screw
- Back off the screw until it doesn't touch the throttle lever.
- Turn the screw in until it touches the secondary throttle lever. Turn it in 1 / 4 turn more.
Fast Idle Speed
- The engine must be normal operating temperature with the air cleaner off.
- With the engine running, position the fast idle screw on the second step against the shoulder of the high step. Plug the EGR Port on the carburetor.
- Adjust the speed by turning the fast idle screw.