Left side view of Tecumseh carb 640084B (#1).
#2 shows the low idle mixing well welch plug (red), atmospheric vent (yellow), primer tube fitting (white), idle restrictor screw (blue) and idle speed screw (black).
The float bowl should be installed with the step parallel to the float hinge and the deeper part toward the float's free end (compare #3 and #9). The dimple in the deep end of the bowl is there to help prevent the float from sticking to the bottom of the bowl.
The small hole in the center of the bowl nut is the main fuel jet (#4).
The larger hole in the side of the bowl nut is the main fuel pickup (#5, black) and the smaller one is the idle fuel transfer port (#5, red).
Fuel from the idle fuel transfer port in the previous photo goes on to the idle fuel pickup (#6). A wire shows the location of the hole. It is directly opposite a ball plug on the outside of the center leg.
The next item in the idle fuel circuit is the idle restrictor screw (#7). A wire shows where the jet orifice intersects a hole in the side of the screw.
#8 shows the idle fuel and air bleed orifices inside the carb throat near the throttle closed position. They are directly opposite the welch plug in #2, red.
After removal of the bowl the float, hinge rod and bowl gasket are visible. (#9). The main nozzle can be seen within the center leg.
With the carb inverted, the free end of the float should rest 11/64 inch from the body of the carb (#10). To adjust, bend the tang on which the needle sits.
The inlet needle is attached to the float with a clip (#11). The long free end of the clip should point toward the choke, or air intake, end of the carburetor.
Shake the float and listen for a sloshing sound, which would indicate a leak and necessitate replacement of the float. If the float does not sit parallel to the carb body, it can be adjusted by bending the tang on which the needle sits (#12).
The main nozzle/emulsion tube can be removed by pressing it out from inside the carb throat (#13).
It has two o-rings. Be sure to fish out the second one if it didn't come out with the tube (#14).
There is a vent hole just before the venturi (#15). A wire shows that the hole connects to the area inside the center leg between the two o-rings of the main nozzle (#16).
The throttle plate is installed with the scribe mark facing outward and in the 12 o'clock position (#17).
A view of the choke lever and linkage from above (#18).