1978 Johnson 4HP outboards Service Manual, Page 27Get this manual
REASSEMBLY OF CARBURETOR AND LEAF VALVES TO MOTOR aAttach leaf plate to powerhead using new gaskets on both sides of plateSee Figure 3-4bUsing new gasket, place carburetor in position on manifold studs and fasten in place with nutscReconnect fuel line to carburetordInstall choke knob 73003
1Grind one jaw here
Figure 3-16
eBack out the cam follower adjustment screw until the throttle valve is closed completelyThen advance the screw until the throttle shaft just begins to rotateLOW SPEED NEEDLE ADJUSTMENT aWith motor at operating temperature, run at slow speed (700-750 rpm) with test propeller in tank or on boatAdjust low speed knob until highest rpm reading and smoothest performance are obtainedAllow 15 seconds for motor to respond to adjustmentbPosition low speed knob so that the pointer is facing down and push back to original position on needle valveWith cam and needle valve correctly adjusted, motor should idle at 600 rpmTHROTTLE TENSION ADJUSTMENT Throttle tension is correct when motor speed remains constant and throttle lever retains its positionTo adjust throttle tension, tighten the throttle tension screw as requiredSee Figure 3-