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SMALL GASOLENE ENGINES

James A. Gray and Richard W. Barrow

Drawings by Robert F. MacFarlane

PREFACE

The intent of this manual is to provide the individual with enough information and guidance so that he can become actively involved with engines. The manual explains, and illustrates, the basic operational theory and service procedures for single-cylinder, air-cooled gasoline engines. The content is organized so that it can foe used as a guide in diagnosing as well as performing minor and major engine service.

The manual is a resource for individuals actively engaged in the maintenance and repair of the small engine and a reference manual for academic instruction and reference.

Numerous tips and checks are presented which should help bridge the gap between theory and actual practice. Handbooks containing specific instructions and specifications are available from the engine manufacturers. These are an invaluable aid to the person servicing the small gas engine.

This manual presents the '"why" and the "how to" in individual packages with illustrations to tell the story. In depth scientific theory is minimized in favor of a fundamental understanding of how it works.

The manual also is intended for the home mechanic who performs his own maintenance and service on the small-engine-powered. labor-saving equipment common today.

Appreciation is expressed to the wives of the authors. Phyllis A. Gray and Virginia L. Barrow, who provided invaluable assistance in the preparation and typing of the manuscript. Sincere gratitude is also expressed to Doug Petty who prepared original illustrations and to George Lambert who assisted with the organization of the written materials.

James A, Gray Richard W. Barrow

Introduction to Single-Cylinder. Air-Cooled Engines

1 The Basic Engine

2 Principles of Combustion

3 Engine Identification

4 Four-Stroke Cycle Theory and Intake Stroke

5 Compression Stroke

6 Power Stroke

7 Exhaust Stroke

8 Two-Stroke Cycle Theory

Basic Engine Testing

9 Compression Testing

10 Spark Testing

11 Basic Carburetor Adjustments

Periodic Maintenance, Engine Tune-Up Procedures, and Storage

12 Lubrication

13 Cooling System

14 Spark Plug Service

15 The Ignition Circuit

16 Electrical Terms

I? Electrical Fundamentals

IS Ignition Primary Circuit

19 Producing Secondary Voltage

20 Flywheel Removal

21 Inspect Flywheel and Key

22 Breaker Points

23 Replace Breaker Points

24 Adjust Armature Air Gap

25 Ignition Timing

26 Parts of the Electronic Ignition

21 Electronic Ignition

28 Carburetion

29 Air-Fuel Mixture

30 The High and Intermediate Speed Circuit

31 The Idle Circuit

32 Carburetor Fuel Supply

33 Built-in Fuel Pump

34 Engine Speed Controls

35 Fuel System Service

36 Carburetor Service

37 Air Cleaner Service

38 Small Gas Engine Storage

39 Measuring Devices

40 The Micrometer

41 Disassemble and Reassemble Instructions and Precautions

Four-Stroke Cycle Engine Service and Overhaul

42 Basic Component

43 Head Gasket Replace merit

44 Engine Overhall; pleniminary Steps

45 Ring Ridge k ;l and Basic Disassembly

46 External Cra r aft Checks and Valve Removal

47 Opening the Crankcase and Piston Removal

4S Cylinder Measurements and Checks

49 Piston Checks

50 Piston Pin and Connecting Rod Checks

51 Crankshaft Checks

52 Main Bearing and Camshaft Checks

53 Valve Lifter and Valve Guide Checks

54 Valve Seat Service

55 Valve Service

56 Reassembly Procedure

57 Installing Piston Rings

58 Installing the Piston Assembly

59 Camshaft and Crankcase Cover Installation

60 Valve Adjustment and Installation

61 Head Replacement and Final Reassembly

Two-Stroke Cycle Engine Service and Overhaul

62 Basic Components

63 Minor Engine Seivice

64 Reed Valve inspection and Service

65 Engine Overhaul (Two-Stroke Cycle Engine)]

66 Cylinder, Piston, and Crankshaft Removal]

67 Checking Wear of Engine Components]

68 Piston Pin and Connecting Rod Checks]

69 Piston Checks]

70 Piston Ring Checks and Installation

71 Seal Replacement and Crankshaft Installation

72 Cylinder and Crankcase Reassembly

73 Final Steps of Reassembly

Battery and Starter Testing

74 The Storage Battery

75 Battery Tests

76 Battery Capacity Tests

77 Test Results

78 Rewind Starters

79 Rewind Starters

80 Electric Starter-Bendix Drive

81 Electric Starter Tests

82 The Starter-Generator

83 Starter-Generator Tests

Generator and Alternator Testing

84 Magnets

85 Electromagnets

86 Residual Magnetism

87 The Charging Circuit

88 Creating Current Flow

89 Diodes

90 Basic Alternator

91 Low Current Alternators

92 Flywheel Alternator System Testing

93 Flywheel Alternator Component Testing

94 Regulated Flywheel Alternator

95 A.C. Lighting Circuit

96 The Generator

97 The Generator Charging Circuit

98 Generator Circuit Variations

99 The Generator and Alternator Compared

100 Basic Generator Tests

Adapted from:

SMALL GAS ENGINES

James A. Gray and Richard W. Barrow

School of Technology Indiana State Univetsitv

Prentice-Hall, Inc., Englewood Cliffs, New Jersey