Carburetor Repair

(Difference between revisions)

Revision as of 06:30, 21 November 2009

Carburetors are complicated, precision analog air/fuel devices. Because it is so easy to make the carburetor worse, the last thing you want to do is dissasemble the carburetor. So first See Carburetor Adjustment. Only proceed to this dissasembly if the carburetor is known bad. For example: rusted, sitting in mud bucket, or all other engine factors are known good but it still runs poorly:

• Engine compression test
• Ignition Timing, Spark/ignition testing
• Vacuum system thorougly inspected

If the carburetor is missing parts or shows signs of being poorly assembled (stripped screws, etc) it may need a partial disassembly for inspection.

Disassembly

Use exploded view as a guide. The numerical sequence may generally be followed to disassemble unit far enough to permit cleaning and inspection.

• Remove staking from bowl cover for easy removal of power piston assy. (22).
• Secondary fuel valve plunger assy. (31) is pressed in carefully. Pry out.

CAUTION: Note sizes of jets and their location for proper assy. (record sizes as you remove them.)

Exploded view: Parts list & breakdown sheet

Numbers correspond to nomenclature below.
Diagram is of manual choke model circa 1973. Other models are slightly different.

1. COTTER PIN - PUMP LEVER ASSY.
2. E CLIP - PUMP LEVER ASSY.
3. LEVER ASSY. - PUMP
4. SPRING- PUMP LEVER
5. SCREW & LOCKWASHER (1) -SERVO DIAPHRAGM ASSY.
6. SCREW & LOCKWASHER (2) -SERVO DIAPHRAGM ASSY.
7. SERVO DIAPHRAGM ASSY.
8. SOLENOID ASSY.- ANTIDIESELING
9. PLUNGER - SOLENOID
10. SPRING - SOLENOID PLUNGER
11. GASKET -SOLENOID ASSY.
12. SPRING - THROTTLE RETURN
13. SCREW & LOCKWASHER (2) -BOWL COVER
14. BRACKET -THROTTLE CABLE
15. SCREW & LOCKWASHER (2) - BOWL COVER
16. BOWL COVER ASSY.
17. PIN - FLOAT
18. FLOAT & LEVER ASSY.
19. GASKET - BOWL COVER
20. PUMP ASSY.
21. BOOT - PUMP
22. POWER PISTON ASSY.
23. NEEDLE, SEAT & GASKET ASSY.
24. SCREEN - FUEL FILTER
25. JET - PRIMARY SLOW AIR BLEED._____
26. JET- SECONDARY SLOW AIR BLEED_____
27. SPRING - PUMP RETURN
28. BALL - PUMP INTAKE CHECK (SMALL)
29. NEEDLE - PUMP DISC. CHECK
30. BOOT - SECONDARY FUEL VALVE
    PLUNGER
31. PLUNGER ASSY. - SECONDARY
    FUEL VALVE
32. GASKET - PLUNGER ASSY.
33. SPRING - PLUNGER RETURN
34. PLUG - SECONDARY FUEL VALVE
35. GASKET - PLUG
36. SPRING - SECONDARY VALVE BALL
37. BALL - SECONDARY FUEL VALVE
38. POWER VALVE
39. GASKET - POWER VALVE
40. JET - PRIMARY SLOW
41. JET -SECONDARY SLOW
42. JET - PRIMARY MAIN AIR BLEED_
43. TUBE - PRIMARY EMULSION (LARGE)
44. JET - SECONDARY MAIN AIR BLEED
45. TUBE - SECONDARY EMULSION (SMALL)
46. PLUG – PRIMARY MAIN JET
47. GASKET - PLUG
48. JET - PRIMARY MAIN JET
49. PLUG - SECONDARY MAIN JET
50. GASKET - PLUG
51. JET - SECONDARY MAIN JET
52. SCREW & LOCKWASHER (2) - THROTTLE BODY
53. SCREW (HOLLOW) - THROTTLE BODY
54. BAFFLE WASHER - HOLLOW SCREW
55. LOCKWASHER - HOLLOW SCREW
56. BOWL ASSY.
57. GASKET - THROTTLE BODY
58. CAP - IDLE LIMITER (WHEN USED)
59. NEEDLE - IDLE ADJUSTING
60. SPRING - IDLE ADJ. NEEDLE
61. THROTTLE BODY ASSY.

Cleaning

Cleaning must be done with carburetor disassembled.

1. Soak parts long enough to soften and remove all foreign material. # Use a carburetor cleaning solvent.
2. Make certain the throttle body is free of all carbon deposits.
3. Wash off in suitable solvent.
4. Blow out all passages in castings with compressed air and check carefully to insure thorough cleaning of obscure areas.

CAUTION:

• be very careful not to leave fuel bowl assy. (56) in cleaning solvent to long because of the glass window rubber seal which is not replaceable.
• Do not soak assemblys with attached plastic parts for a long period of time.
• Do not soak any parts containing rubber or diaphragm and solenoid assemblys.

Reassembly

Reassemble in reverse order of disassembly. Note special instructions and follow numerical outline in making adjustments necessary for carburetor being serviced.

Special Instructions

• Idle adjusting needle (59) - turn needle in until lightly seated then back out 2 turns. (do not install idle limiter caps at this time.)
• Baffle washer (54)- when installing, baffle blocks primary side of passage.
• Secondary fuel valve plunger assy. (31) - when installing aline opening in sleeve with passage in fuel bowl.
• Pump return spring (27) - install with cross wire to the bottom of pump cylinder.
• Power piston (22) - after installing lightly restake casting around washer.
• Pump plunger (20) - before installing flex leather outward slightly. Soak cup in gasoline, kerosene or oil for a few minutes prior to placing in carburetor.
• Pump lever (3) - hook pump rod in inner hole of lever.