Outdoor Power Equipment, Small Engine, Lawn Mower Repairs, Troubleshooting and Safety

The Kohler part number is stamped on top of the carburetor or on the mounting flange (#1, white). The idle speed screw limits how far toward closed the throttle can travel (#1, red). The main fuel mixture adjusting screw (or needle) extends from the top of the carb (#1, yellow) down to the main jet in the carb bowl. The idle fuel mixture adjusting screw (#1, blue) extends directly to the primary idle fuel discharge port in the carb bore.

Fuel enters the carb via the fuel inlet fitting (#2, blue). The choke lever is at the air intake end (#2, yellow) and the throttle lever is at the top rear of the carb (#2, red). The fuel bowl (#2, white) holds a supply of fuel at a fixed level.

The float (#3) inside the fuel bowl maintains a constant level of fuel in the bowl. The float should sit parallel to the carburetor body when inverted. If it does not, the float can be adjusted by bending the tab which rides on the inlet needle. When the carb is held upright the float should hang down 1-1/32 inch from the carb body to the lowest point of the float. If it does not, the float can be adjusted by bending the tab which limits its drop.

Slide the float hinge pin (#4, blue) out either side and the float can be removed. Fuel for both the main and idle circuits enters through holes in the center pedestal (#4, green).

A baffle (#5) prevents fuel from splashing up into the bowl vent passage.

The bowl vent (#6, green) brings atmospheric pressure from the air intake. The inlet needle is pushed upward by the float into the brass inlet seat (#6, yellow) thereby slowing fuel flow into the bowl. The adjustable main jet (#6, red) meters how much fuel is delivered to the main and idle fuel circuits. The bowl gasket (#6, blue), separate from the baffle, provides a seal against leakage.

The inlet needle (#7, white) has a conical rubber tip that should form a fuel-tight seal with the inlet seat when pushed upward by the float.

The main fuel adjusting needle is a tube with several holes in its side and a closed pointed tip. The tip of the main fuel adjusting screw fits into the main jet, acting as a metering valve. The main jet is actually the bottom portion of the emulsion tube. The fuel flows around the tip and up through the tube where it mixes with air from the main air bleed. The mixture exits the tube at the nozzle and enters the venturi. The hole near the tip of the needle (#8, red) picks up fuel for the idle, or low speed, circuit. The idle fuel flows inside the needle, mixes with air drawn into the idle air bleeds (#8, yellow). This mixture exits at the top holes of the of the tube (#8, white).

The main air bleed (#9, yellow and red) delivers air to the emulsion tube where it mixes with the main fuel supply. The bowl vent (#9, green) connects the bowl to outside air. The venturi size is cast into the carb (#9, blue).

A fuel and air mixture that has traveled up through the main needle continues to the off-idle ports through a passage in the carb body (#10, red).

The idle fuel mixture exits the main needle (#11, white), flows through a passage in the body (#11, blue) and arrives at the off-idle ports behind a welch plug (#11, yellow). Depending on throttle position some fuel may be discharged into the intake airstream here while the remainder flows to the primary idle fuel discharge port metered by the idle fuel mixture adjusting screw (#11, red).

The idle fuel discharge ports deliver fuel into the carb throat. The primary port (#12, yellow) is directly opposite the mixture screw and operates when the throttle is very nearly closed. The off-idle, or secondary, port (#12, blue) is opposite the welch plug and delivers more fuel as the throttle plate opens slightly, until the main fuel circuit takes over. The edges of the throttle plate are chamfered. Mark the plate if it is to be removed and use threadlocker during assembly. 'K' is stamped on the plate and faces outward as shown (#12, red).

The edges of the choke plate are chamfered. Mark the plate if it is to be removed and use threadlocker during assembly. 'K' is stamped on the plate and faces outward as shown (#13, yellow). A detent spring and ball are used to hold the choke open.