1971 Johnson 4HP Outboard Motors Service Manual, Page 21Get this manual
REASSEMBLY OF CARBURETOR AND LEAF VALVES MOTOR Attach leaf plate to power head using new gaskets both sides of plateSee Figure 3-4 Using new gasket, place carburetor in position manifold studs and fasten in place with nutsReconnect fuelline to carburetordInstaH choke knob
Start engineNOTE AHow engine to reach normal operating temperature running in tank with test propeHer at one-half throttleRun engine at fuH throttleUsing tachometer, adjust high-speed needle until best high-speed setting is obtainedLOW -SPEED NEEDLE NOTE High-speed needle must correctly adjusted described above before low-speed needle adjustment is begunWith motor at operating temperature, run at slow speed (700-750 rpm) with test propeHer in tank or boatAdjust low-speed knob until highest rpm reading and smoothest performance are obtainedAllow 15 seconds for motor to respond to adjustmentAdjustment of high-speed needle MUST repeated after final low-speed needle adjustmentfoHower Install adjustment knobDO disturb position of needlePosition high speed knob that the pointer is facing straight and push back to original position needle valvePosition low speed knob that the pointer is facing down and push back to original position needle valveWith and needle valve correctly adjustedmotor should idle at 600 rpmTHROTTLE TENSION ADJUSTMENT Throttle tension is correct when motor speed remains constant and throttle lever retains its positionadjust throttle tension, tighten the throttle tension screw requiredSee Figure 3-16