Tecumseh series 1 carb viewed from above (#1). The idle adjustment needle (green), idle speed screw (blue), and primer tube (red) are visible, as well as the governor - throttle link and the choke lever.
Carb bowl and bowl nut viewed from the bottom (#2). The step in the bottom of the bowl should be positioned parallel to the float hinge rod shown in the next photo, with the deeper area away from the hinge. The small dimple in the deeper side of the bowl is there to help prevent the float from sticking to the bottom of the bowl.
The float and hinge rod viewed from the bottom (#3). After removing the bowl gasket, the hinge rod can be slid out to either side and the float and inlet needle lifted out.
With the carb inverted, the free end of the float should rest 11/64 inch from the body of the carb (#4). To adjust, bend the tang on which the needle sits (#7).
The bowl nut and main jet needle are assembled in the order shown (#5. The initial setting of the needle is 1 1/2 turns out from lightly seated.
Close-up view of the bowl nut (#6). The larger hole on the side of the nut is the main fuel pickup. The smaller hole is the idle fuel transfer port. The hole within the center of the nut is the main jet. These passages in the bowl nut are the most common source of trouble in the carb. They must be free of debris, gum or varnish.
The inlet needle is attached to the float with a spring clip (#7). When assembled, the straight end of the clip should point toward the air intake side (choke side) of the carb. Check the float for leaks by shaking it. If you hear liquid sloshing around inside it, replace it. The float may also become crushed by water in the bowl freezing in cold weather.
This carb uses a replaceable rubber seat for the inlet needle (float needle) (#8). The seat is inserted with the grooved side facing inward. Any debris or wear on the needle or seat will cause a poor seal resulting in a high fuel level in the bowl. This may lead to a rich running condition, flooding, or after a time the crankcase can fill with fuel. If your oil level seems high and/or is thin and smells like gas, you probably have a bad float, needle or seat.
A ball plug (#9) indicates where the idle fuel pickup hole was drilled through into the inside diameter of the center leg.
#10 shows the idle fuel pickup hole within the center leg.
A cutaway view of a typical idle fuel pickup hole within the center leg (#11). Fuel for the low-speed circuit comes through the bowl nut idle fuel transfer hole (#6), through this hole, and on to the progression holes in #13. When this hole is clogged the engine might not run at low speed and may surge at high speed. Shooting carb cleaner into the hole from which the low-speed jet was removed should result in a stream squirting out this hole.
The brass main nozzle in the center of the center leg is pressed into place on this carb and is not removable (#12).
The throttle plate is installed with the scribe mark facing outward and in the 12 o'clock position for 2-7 HP engines, 3 o'clock position for 8-17 HP engines (#13). The low-speed progression holes are shown toward the right.
#14 shows how the throttle return spring is hooked into place.
#15 shows the Welch plug (blue) covering the idle mixing well, idle mixture screw (yellow), external vent (red) and the primer tube fitting (green).
Idle mixture screw, spring, washer, seal (#16). The idle screw preset is 1 turn out from seated.
Choke plate installed with the flat edge and open section down, hole toward fuel inlet (#17).