Note

All gaskets, rubber gaskets, seals and plastic parts, including items 18, 22 and 41, should be removed and only metal parts cleaned in Gunk Hydroseal cleaning solution.

All channels and orifices in the carburetor and pump-body castings should be cleaned with compressed air. DO NOT use wires or drills to clean small holes. These might cause burrs or change the size of the holes.

Inspect all parts for wear or damage paying particular attention to the following:

Examine pump body casting for breaks and cracks.

The inlet control lever must rotate freely on the fulcrum pin and forked end must engage slot in inlet needle (see Fig. 3F-8A). The spring (34) should not be stretched or distorted.

Inspect the inlet needle (¿2) cone point for wear and scratches. Inspect the lever (29) contact end for burrs and wear.

ASSEMBLING CARBURETOR (See Fig. 3F-8)

Make certain that all parts are kept clean during reassembly. Do not use cloths to wipe or dry parts. Lint or threads can easily block small orifices. Welch plugs should be seated with a flat-end punch of a slightly smaller diameter than the welch plug. The seated plug should be flat, not concave, to assure a tight fit around the circumference.

The metering spring (34) should be seated into the counterbore in the body casting, and located on the protrusion on the inlet control lever (29). The lever should be adjusted flush with the floor of the metering chamber by bending diaphragm end of lever as necessary.

Two torque values are important: (1) the inlet seat assembly (32) should be tightened to 40-45 inch pounds; and (2) the accelerating-pump channel plug (19) should be tightened to 23-28 inch pounds.

TROUBLE SHOOTING GUIDE (See Fig. 3F-8)

The following symptoms and possible causes with corrective service can be used as a guide in servicing the carburetor.

A. Idle System

1. Idle operation too lean.

(a) Dirt in idle fuel channels - blow out with compressed air.

(b) Intermediate adjustment (35) closed or adjusted too lean - readjust.

(c) Welch plug (6) or channel plugs (5) missing or not tightly sealed - re-seat or replace plugs.

(d) Nozzle check valve (41) not sealing - blow out with compressed air, or replace. (See "Check List" No. 5.)

2. Idle operation too rich.

(a) Carburetor flooding - see Item E.

(b) Idle adjustment screw (24) point damaged - replace the adjustment.

(c) Idle adjustment hole damaged, forced oversize, or casting cracked in the idle port area - replace carburetor.

B. Intermediate System

1. Lean operation at steady speeds between 15 and 65 m.p.h.

(a) Intermediate adjustment (35) adjusted too lean -readjust.

(b) Dirt in intermediate fuel ports or supply channels - remove welch plug (6) and channel plugs (5) and blow out with compressed air.

(c) Welch plug (6) or channel plugs (5) not tightly sealed - re-seat or replace plugs.

(d) Nozzle check valve (41) not sealing - blow out with compressed air, or replace. (See "Check List" No. 5.)

(e) Intermediate adjustment packing (36) missing or damaged - replace.

(f) Economizer check ball (22) stuck closed - remove welch plug (8) and check ball (22) and blow out channel with compressed air. (See "Check List" No. 10.)

2. Rich operation at steady speeds between 15 and 65 m.p.h.

(a) Intermediate adjustment (35) adjusted too rich -readjust.

. (b) Fixed main jet (39) too large, not tightly in place or missing - seat firmly, or replace jet.

(c) Carburetor flooding - see Item E.

(d) Nozzle check-valve welch plug (6) not tightly sealed - re-seat or replace.

(e) Choke valve partially closed - see that choke friction spring (10) and choke friction ball (9) are correctly assembled.

C. Nozzle System

1. Lean operation at speeds above 60 m.p.h.

(a) Dirt in nozzle system - remove main fuel jet plug screw (40) and blow channels out with compressed air.

(b) Main fuel jet (39) too small or damaged - replace.

(c) Main fuel jet plug screw (40) not tightly sealed -tighten to stop air leak.

(d) Nozzle check valve (41) damaged - replace. (See "Check List" No. 5.)

(e) Nozzle check valve (41) not seated correctly in casting - re-seat flush with nozzle-well surface.

2. Rich operation at speeds above 60 m.p.h.

(a) Main jet (39) too large, not tightly in place or missing - seat firmly or replace.

(b) Carburetor flooding - see Item E below.

(c) Economizer check ball (22) not seating - remove welch plug (8) and check ball (22) and blow channel out with compressed air. (See "Check List" No. 10.)

D. Accelerating Pump System 1. Lean acceleration.

(a) Incorrect carburetion adjustment - readjust idle (24) and intermediate adjustments (35).

(b) Dirt in acceleration fuel channels - blow out all channels in diaphragm cover (18) and the accelerating pump discharge channel in the body casting. (See "Check List" No. 1.)

(c) Accelerator pump assembly (1) damaged or worn - replace assembly. (See "Check List" No. 1.)

(d) Diaphragm cover plug screw (19) loose or missing - tighten or replace.

(e) Diaphragm (17) flap check valves damaged or worn - replace diaphragm.

(f) Economizer check ball (22) stuck closed - remove welch plug (8) and check ball (22) and blow channel clean with compressed air. (See "Check List" No. 10.)

E. Carburetor Flooding

1. Dirt in inlet needle and seat assembly (32) - remove and clean, or replace. (See "Check List" No. 3.)

2. Inlet seat gasket (33) missing or damaged - replace.

3. Inlet control lever (29) not correctly adjusted -readjust lever flush with metering chamber wall. (See "Check List" No. 9.)

4. Diaphragm (17) incorrectly installed - replace or correct installation.

5. Inlet control lever pin (30) loose or not correctly installed - tighten retaining screw (31) and correct installation.

6. Inlet control lever (29) tight on lever pin (30) -replace damaged part, or clean dirt from these parts.

7. Inlet needle or seat (32) damaged or worn - replace the assembly.

F. General Operation

1. Lean operation in all speed ranges.

(a) Filter screens (23) plugged or dirty - clean or replace.

(b) Inlet control lever (29) incorrectly adjusted -readjust lever flush with wall of metering chamber. (See "Check List" No. 9.)

(c) Diaphragm cover plate (18) loose - tighten six screws (20).

(d) Air leak in metering system - all channel plugs, plug screws, and lead plugs to be tightly sealed.

(e) Inlet tension spring (34) stretched or damaged -replace.

2. Rich operation in all speed ranges.

(a) Carburetor flooding - see Item E.

(b) Choke valve not staying fully open - see that choke friction spring (10) and friction ball (9) are assembled correctly.

(c) Inlet control lever (29) incorrectly adjusted -readjust lever flush with wall of metering chamber. (See "Check List" No. 9.)

model m carburetor

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