Operation

The float system is shown in Figure 3-74. Fuel from gas tank passes through fuel valve (21) into float chamber (29). The fuel entering causes float to rise until it shuts off fuel valve, stopping flow at a level pre-determined by float level setting.

Bend float Tab

Bend float Tab

Figure 3-72

21. Fuel valve 23. Float

29. Float chamber

Figure 3-74. Carburetor Float System

The slow system is shown in Figure 3-75. It functions at idle, low and intermediate speeds when throttle valve is closed or only partially open. At idle, fuel enters main jet (26) and, after being metered there, enters slow jet (25) where it is metered again. The fuel from jet (25) enters bleed tube portion of slow jet where it mixes with air from slow air passage. The fuel mixture is regulated by adjusting screw (12). When throttle valve is closed, fuel mixture flows into venturi almost entirely through idle port. As throttle valve gradually opens, fuel mix discharge is transferred to bypass. Note that slow jet bleed tube is actually a part of slow jet (25).

The main system also is shown in Figure 3-75. The main system functions at intermediate and high speeds as the throttle valve opens further. The fuel is metered by main jel (26) and enters main jet bleed tube portion of main nozzle where it mixes with air entering through main jet aii passage. This fuel air mixture then exits from main nozzle (24) into venturi.

The accelerating pump system is shown in Figure 3-76. It works with sudden throttle openings (rapid accelerations) to quickly inject fuel into carburetor to provide extra fuel for accelerating,

Rapid throttle action pushes pump rod (7) down, flexing diaphragm (31). This flexing action compresses fuel underneath diaphragm, forcing it up past check valve and out pump nozzle into venturi. The check valve prevents back-flow while pump nozzle meters flow. Spring action then returns diaphragm to its original position. As diaphragm returns, a new supply of fuel flows in under diaphragm so system will be ready to repeat cycle with next rapid throttle action.

The choke system, composed of choke valve and associated parts, is shown in Figure 3-75. The choke is manually set by pulling choke button out. By adjusting choke button, choke valve can be positioned either completely closed (fully choked for cold engine), partially open, or fully open (off for warm engine).

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