Cleaning and Inspection
Dirt, gum, water or carbon contamination in the car-burettor or the exterior moving parts of the carburettor are often responsible for unsatisfactory performance. For this reason, efficient carburation depends upon careful cleaning and inspection.
The cleaning and Inspection of only those parts not included in the carburettor overhaul repair kit are covered here. All gaskets and parts included in the repair kit should be installed when the carburettor is assembled and the old gaskets and parts should be discarded.
Wash all the carburettor parts (except the accelerating pump diaphragm, the power valve or power valve dia-phragm, and the anti-stall dashpot assembly) In clean commercial carburettor cleaning solvent. If a commercial solvent is not available, lacquer thinner or denatured alcohol may be used.
Rinse the parts in kerosene to remove all traces of the cleaning solvent, then dry them with compressed air. Wipe all parts that cannot be Immersed In solvent with a clean, soft, dry cloth. Be sure all dirt, gum, carbon, and other foreign matter are removed from all parts.
Force compressed air through all passages of the car-burettor. Do not use a wire brush to clean any parts or a drill or wire to clean out any openings or passages in the carburettor. A drill or wire may enlarge the hole or passage, changing the calibration of the carburettor.
Check the choke shaft for grooves, wear, and excessive looseness or binding. Inspect the choke plate for nicked edges and for ease of operation and free it if necessary. Check the throttle shafts in their bores for excessive looseness or binding and check the throttle plates for burrs which prevent proper closure.
Inspect the main body, air horn, nozzle bars and booster venturi assemblies, choke housing and thermostatic spring housing, power valve cover, accelerating pump cover, secondary operating diaphragm cover and the main body for cracks.
Check the float for leaks by holding them under water that has been heated to just below the boiling point. Bubbles will appear if there is a leak. If a float leaks, replace It. Replace the float if the arm needle contact surface is grooved. If the float is serviceable, polish the needle contact surface of the arm. Replace the float shafts if they, are worn.
Replace all screws and nuts that have stripped threads.
Replace all distorted or broken springs.
Inspect all gasket mating surfaces for nicks and burrs.
Repair or replace any parts that have a damaged gasket surface.
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Inspect the idle tubes in each nozzle bar assembly. If they are plugged, bent, or broken, replace the booster venturi and nozzle bar assembly.
Inspect the rubber boot of the anti-stall dashpot for proper installation in the groove of the stem bushing. Check the stem movement for smooth operation. Do not lubricate the stem. Replace the assembly if it is defective.
Reassembly
Make sure all holes in the new gaskets have been properly punched and that no foreign material, has adhered to the gaskets. Make sure the accelerating pump diaphragm is not torn or cut.
The carburettor assembly is shown in Fig. 32.
Main body
1. If the throttle plates were removed, install the over-travel anti-friction bushing over the boss on the over-travel lever. Place the over-travel spring, with the shortest tang end first, over the bushing and boss on the over-travel lever. Place the short tang of the spring under the lug on the accelerator over-travel lever.
2. Slide the over-travel lever and spring assembly on the throttle shaft and bushing. Hook the longest tang of the spring under the closed throttle lug of the throttle lever (Fig. 30). Install the over-travel lever retainer. Slide the throttle shaft assembly into the main body.
3. Referring to the lines scribed on the throttle plates, install the throttle plates in their proper location with the screws snug, but not tight. Close the throttle plates. Invert the main body, and hold it up to the light. Little or no light should show between the throttle plates and the throttle bores. Tap the plates lightly with a screwdriver handle to seat them. Hold the throttle plates closed and tighten and stake the retaining screws. When staking the screws, support the shaft and plate on a block of wood or a metal bar to prevent bending of the shaft.
4. If necessary, install the engine idle screw retainer and the screw on the fast idle adjusting lever. Install the distributor vacuum passage fitting.
5. Install the anti-stall dashpot, if so equipped.
6. Place the fast idle lever assembly on the throttle shaft and install the retaining washer and nut (Fig. 19).
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