1981 Johnson/Evinrude 4HP Outboards Service Manual, Page 20Get this manual
DESCRIPTION FUEL FLOW The fuel system consists of fuel tank mounted on the powerhead, fuel filter, and carburetorFuel flows, gravity-fed, from the tank to the carburetorCARBURETOR The carburetor is single-barrel, float feed typeThe high speed jet is fixed, and the low speed jet is adjustableThe carburetor has manual chokeThrottle linkage is synchronized with the magneto by cam on the magneto armature plate
dropped to predetermined point on the compression strokeSee Figure 3-1CHOKE The carburetor is fitted with manual choke to reduce the ratio of air to fuel for cold startsA choke valve in the air inlet of the barrel is mounted on the choke shaftWhen the choke knob is pushed in, the choke valve is held open, allowing air to pass freely through the inletWhen the choke knob is pulled out, the choke valve is closed, restricting the flow of air to the carburetor