Vacuum Step-Up Piston

Fig. 9 Checking step-up piston. 1983-84 carburetors:

Fig. 10 Vacuum step-up piston adjustment:

1. On 1983-84 models, if step-up piston assembly is removed or mechanical rod lifter adjustment is disturbed, step-up piston should be readjusted as follows:
a. Remove step-up piston cover plate and gasket.
b. Remove rod lever lock screw, then the step-up piston assembly.
c. Adjust gap in step-up piston by turning allen head calibration screw on top of piston, Fig. 9. Gap should be .035 inch. Record number of turns and direction to obtain specified gap. This gap must be reset to it's original position after final vacuum step-up piston adjustment has been complete.
d. Install step-up piston assembly and rod lifter lock screw.
2. On all models, back off curb idle screw until throttle valves are completely closed. Count number of turns so that screw can be returned to its original setting.
3. Fully depress piston and while applying moderate pressure on rod lifter, tighten rod lifter screw, Fig. 10.
4. Release piston and rod lifter and reset curb idle screw.
5. On 1983-84 models, reset allen head calibration screw on top of step-up piston as recorded in step 1.