All inspections and tests should be performed, in the sequence shown below, before further disassembly or repairs are made.


1. The accelerator pump should be inspected for proper operation first. Remove air cleaner, prime carburetor by inserting a toothpick through small hole in bottom of plastic pump cover and gently working diaphragm several times. Operate the throttle lever both rapidly and slowly several times, with the fuel valve turned on. The pump should deliver a strong and constant jet of fuel with each stroke. Failure to do so indicates diaphragm valves or pump plunger as being defective.

2. In cleaning of high, intermediate and low speed channels, the following procedure, most likely, will dislodge any loose dirt lodged in the passages.

Remove high speed screw plug located on rear side of carburetor, opposite intermediate adjustment needle. Lightly seat intermediate needle and apply air hose pressure (90 pounds maximum) to screw plug hole. Open intermediate and idle needles three or four turns and again apply 90 pounds maximum air pressure. Reset both adjustment screws (see Adjusting Carburetor). Evaluate carburetor's performance by road testing.

3. Check inlet needle and seat for leakage, as follows:

See that all plastic cover screws are tight. Remove fuel and vent lines, install bulb tester, Part No. 94750-68, to carburetor fuel inlet fitting, plug vent fitting with finger and pressurize tester noting any leakage. A moistened needle and seat should hold 1 to 1 -1 /2 lbs approximately, and release at approximately 3 to 5 lbs. A dry needle and seat will not hold as well as a moist one. See Figure 3-59.

Figure 3-59. Checking Inlet Needle and Seat for Leakage


4. Inspect intermediate adjustment needle and spring to see if spring coils are binding before needle seats. If needle does not seat grind a small amount of material from each end of spring. You can check to see if needle is seating by applying blue dye to needle taper and screwing down lightly into seat and noting mark on needle taper.

5. Check main nozzle ball check valve for leakage, as follows:

Seal one side of venturi with finger and apply alternate pressure and vacuum by mouth using grommet end of tool, Part No. 96960-68, sealed in venturi as shown in Figure 3-60.

Vacuum should release ball, and pressure should seat ball in nozzle assembly.

If leakage is evident, carburetor must be disassembled and main nozzle check valve assembly replaced.

Figure 3-60. Checking Main Nozzle Ball Check Valve for Leakage

To replace main nozzle, puncture welch plug with pointed tool, avoiding center, as shown in Figure 3-61. Remove nozzle welch plug and use stepped end of punch. Part No. 96962-68, on nozzle, tapping it through into venturi using plastic hammer. See Figure 3-62. Use larger end of tool to install the new check valve in the same manner. See Figure 3-63.

6. Inspect idle needle and seat in carburetor bore for any distortion or a cracked casting.

7. Inspect choke relief disc (upper half of choke) for distortion or stress cracks at the area rotating on choke shaft.

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