The Tecumseh Series 11 carb shown here has fixed (non-adjustable) idle and main fuel circuits. The fixed main jet is drilled into the bowl retaining nut (#6) and the external access hole is sealed with a ball plug (#5). A fixed restrictor jet meters the fuel for the idle circuit (#19). The series 11 has a serviceable main nozzle (#17). It also has a black restrictor cap (#1, in white box) whereas all others will be gray. An additional jet is found on the center leg (#18, black) as well as a second welch plug above the fuel line which covers a metering jet (#18, white).
A rubber gasket goes between the air filter base (collar) and the carburetor (#2).
The carburetor/governor linkages are as shown in #3. Once the carb is separated from the engine and fuel line, the links can be unhooked from the governor lever by moving the carb away from the engine and to the right.
The governor adjustment lever can be bent to change the high r.p.m. setting (#4). Bending it away from the carb increases engine speed.
The fuel bowl (float bowl) (#5) should be positioned so that the step is parallel to the float hinge, with the deeper part away from the hinge (#8). Remove the bowl retaining nut to take off the fuel bowl.
The bowl retaining nut (#6) has a number of holes that must be clear. The center hole (red) is the main jet. The side hole (blue) is the idle fuel transfer port.
#7 shows one of the bowl nut's main fuel pickup holes and the idle fuel transfer hole.
The float is held in place by, and pivots on, a hinge rod or pin (#8).
The bowl gasket (#9) prevents fuel from leaking and also must provide a good seal for the primer to work properly.
With the carb inverted, the free end of the float should rest float should rest 11/64 inch from the body of the carb (#10) and the needle moves up and down freely with the float.
The float is removed from the body by sliding out the hinge rod (#11). When you lift the float from the body, the float needle (inlet needle) will come with it and may slide off. Be careful not to lose it.
With the carb inverted, the free end of the float should rest float should rest 11/64 inch from the body of the carb. To adjust, bend the tang on which the needle sits. (#12).
The float needle is held to the float by a spring clip (#13). The long end of the clip should face toward the choke, or air intake, side of the carburetor.
The inlet seat has a groove on one side (#14, left) and on the other side the center hole is chamfered (#14, right).
The inlet seat is installed with the grooved side facing inward (#15). The float needle mates with the outward facing chamfered hole of the seat.
The tip of the main nozzle can be seen in the center of the venturi (#16). To remove the nozzle press the tip down with the flat blade of a screwdriver.
The hole at the 10 o'clock position (#16) is the vent for the primer and bowl. This carb uses a tygon tube to extend the vent farther out into the air cleaner.
The removable main nozzle has two o-rings (#17). Be sure not to leave one behind in the center leg, and clean out any bits of rubber that may have been left behind.
In #18 the yellow square shows the location of a ball plug which seals the hole where a passage was drilled into the inside of the center leg. In #19 a wire indicates where that passage is inside the center leg.
Also, in #18, the black square shows the location of a passage for fuel flow during warm-up.
Again, in #18, the white square shows the location of a plastic metering jet (which is normally covered by a welch plug) for fuel flow during warm-up. This passage will rarely need to be cleaned, but if necessary, use a 0.012" wire. Harsh cleaning solutions may damage or distort this jet.
A wire indicates the location of the idle fuel pickup passage (#19). Carb cleaner squirted into the hole from which the idle restrictor jet was removed should shoot out this hole. When this passage is restricted the engine may surge at high or low speed, or stall at low speed.
After removing the black plastic cap (#1), the idle restrictor jet or pilot jet (#20) is unscrewed from the carb. A small hole in the end of the jet intersects with the larger hole in the side of the jet, as shown by a 0.012" wire. When this jet is clogged the engine may surge at high or low speed, or stall at low speed.
#21 shows the carb body with primer bulb, idle well welch plug and idle restrictor jet removed. The top four holes in the idle mixing well pass straight into the carb throat and the lower one intersects with the restrictor jet.
Four holes drilled through from the idle well can be seen near throttle closed position (#22, circle). Carb cleaner squirted into the hole from which the idle restrictor jet was removed should shoot out these holes (these seldom get clogged).
The throttle plate (shutter) (#22, rectangle) has a scribe mark which should face outward and be in the 12 o'clock position for 2 thru 7 HP engines, or in the 3 o'clock position for 8 thru 17 HP engines.
The throttle return spring (#23) keeps the throttle normally closed.