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

The Tecumseh series 9 carburetor can be identified by the stepped primer bulb (#4), the simple idle system (#2), and a serviceable main nozzle (#14). It has no adjustments for main or idle fuel mixture. The main jet (#7) is part of the bowl nut.

The low idle mixing well (#2, black) and the idle jet hole (#2, blue) are not machined.

The primer bulb retainer can be removed by prying up each tooth successively with a hooked tool (#2, green). However, the only reason to do so is to replace a damaged bulb.

With the primer bulb removed (#3), the two upper passages can be seen to connect to the carb's air intake (#13, yellow). The passage within the center of the primer chamber leads to the cavity above the welch plug in the fuel bowl. Under normal conditions the passages all meet behind the primer bulb, thereby venting the fuel bowl. However, when the primer bulb is partly depressed, the step of the bulb seals against the casting, and further depression of the bulb forces air into the fuel bowl, which in turn forces fuel up the nozzle.

The primer bulb and retainer (#4).

The fuel bowl is installed with the step parallel to the float hinge and the deeper part at the free end of the float (#5). A ball plug seals the hole where the main jet was drilled through the bowl nut (#7).

The bowl nut has four holes that must be clear (#6). The two larger holes below the threads are the main fuel pickup. The smaller one above the threads is the idle fuel transfer (or delivery) port. Fuel goes from this port to the idle fuel pickup hole shown in #12.

The hole in the center of the bowl nut is the main jet (#7).

With the carb inverted, the free end of the float should rest float should rest 11/64 inch from the body of the carb (#8). To adjust the float bend the tang where the float meets the inlet needle.

The inlet needle or float needle is attached to the float with a clip (#9). The clip should be installed with the long end pointing toward the air intake or choke end of the carb.

The inlet needle seat is installed with the grooved side inward (#10). The side facing outward has a chamfered hole which mates with the needle.

The center leg of the carb has a ball plug which seals the place where the idle fuel pickup was drilled into the interior of the center leg (#11).

The idle fuel pickup is located directly opposite the ball plug on the center leg (#12). When this hole is clogged the engine may surge at high or low speed, or stall at low speed.

Looking into the intake end of the carb, you can see the bowl vent (yellow), top of the nozzle (white), and the nozzle vent or air bleed (black) (#13). The nozzle air bleed leads to the area between the nozzle o-rings.

The nozzle can be pressed out from the inside of the carb throat with the flat blade of a screwdriver (#14). It has two o-rings. One will likely remain in the center leg and need to be fished out.

The idle fuel discharge port is located just beyond the throttle plate at the 7 o'clock position (#15).

The throtle plate has a coined edge for a better seal and is installed with the scribe mark facing outward and in the 12 o'clock position (#16).

The throttle return spring moves the throttle to the closed position (#17).