1971 Johnson 4HP Outboard Motors Service Manual, Page 16Get this manual
LEAF VALVES The leaf valves time the injection of the fuel mixture into the crankcase opening only when the pressure in the crankcase has dropped to predetermined point the compression strokeSee Figure 3-1 The carburetor is fitted with manual choke to reduce the ratio of air to fuel for cold startschoke valve in the air inlet of the barrel is mounted the choke shaftWhen the choke knob is pushed in, the valve is held open, allowing air to pass freely through the inletWhen the choke knob is pulled out, the valve 1s closed, restricting the flow of air to the carburetor
REMOVAL OF CARBU RETOR AND LEAF VALVE ASSEMBLY
Remove motor coveroff high and low speed knobsRemove cotter and hinge pin to remove choke knobSee Figure 3-2
Figure 3-3Carburetor Attaching Nuts
Figure 3-4Removing Manifold and Leaf Plate Assembly