Outdoor Power Equipment, Small Engine, Lawn Mower Repairs, Troubleshooting and Safety
Disassembly, Cleaning and Repair of Tecumseh Series 1 Emission Carb 640084B Used on 5.0 HP 4-cycle Snow King Engine
- Quick notes:
- This carb has fixed (non-adjustable) low idle and main jets.
- The main jet is part of the bowl retaining nut.
- The main nozzle/emulsion tube is replaceable.
- The main nozzle and float are non-metallic.
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- #1. Left side view
Left side view of Tecumseh carb 640084B (#1).
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- #2. Welch plug (red), restrictor screw (blue)
#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).
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- #3. Float bowl
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.
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- #4. Main jet is part of bowl nut
The small hole in the center of the bowl nut is the main fuel jet (#4).
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- #5. Main fuel pickup and idle transfer port
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).
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- #6. Wire shows idle fuel pickup
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.
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- #7. Idle restrictor screw
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.
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- #8. Idle orifices
#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.
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- #9. Float and bowl gasket
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.
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- #10. Float sits parallel to body
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.
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- #11. Clip attaches needle to float
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.
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- #12. Bend tang to adjust float
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).
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- #13. Main nozzle / emulsion tube is serviceable
The main nozzle/emulsion tube can be removed by pressing it out from inside the carb throat (#13).
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- #14. Nozzle with o-rings
It has two o-rings. Be sure to fish out the second one if it didn't come out with the tube (#14).
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- #15. Wire shows air vent
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).
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- #16. Vent enters between o-rings
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- #17. Throttle plate, scribe mark
The throttle plate is installed with the scribe mark facing outward and in the 12 o'clock position (#17).
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- #18. Choke linkage viewed from above
A view of the choke lever and linkage from above (#18).