3to 11hp 4-cycle l-head engines - Small Engine Suppliers

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GENERAL INFORMATION CHAPTER 6 ELECTRICAL SYSTEMS The electrical system consists of three main elements: a battery, a starting circuit, and a charging circuit. The battery is part of both the starting and charging circuit. The battery should be checked before going into any extensive starter or charging system checks. If a battery has a shorted cell, overcharging can result, and the regulator or rectifier may appear to be at fault. If a cell has an open or high resistance connection, the electric starter operation will be affected. The power source used to provide the energy to turn an electric starter motor on Tecumseh engines is either 120 volt A.C. current or 12 volt D.C. An A.C. starter circuit utilizes a 120 volt power source instead of a battery. The 12 volt battery models require a charging system to maintain proper battery charge. The starting circuit includes the battery, battery cables, starter or ignition switch, safety switches, and an electric starter motor. The charging system consists of alternator charge coils, rectifiers or diodes, regulator, ignition switch, flywheel magnets, and a battery. All engines that have a charging system will use a combination of some or all of these features. OPERATION STARTING CIRCUIT AND ELECTRIC STARTERS After all of the safety interlock switches have been activated, the starter switch will complete the circuit. A strong magnetic force is produced by the electrical current running through the armature windings. The armature magnetism repels the magnetism produced by the permanent field magnets of the electric starter. The repelling magnetic forces cause the armature to rotate, moving the drive pinion laterally on the splined armature shaft, meshing the starter pinion gear with the flywheel ring gear. When the drive pinion contacts the stop at the end of the armature shaft, the pinion rotates along with the armature shaft to crank the engine. The armature and pinion remain positively engaged until the engine fires and the flywheel rotates faster than the armature. The greater momentum of the flywheel throws the starter pinion gear out of mesh and forces the starter pinion back to the disengaged position. After the switch is released, the starting circuit is opened and the armature coasts to a stop. A small anti-drift spring holds the pinion in the disengaged position (diag. 1). HOUSING SPRING RETAINER BRUSH CARD RETAINER BRUSHES BRUSH SPRINGS LOCK NUT BOLT SPRING GEAR DUST COVER END CAP WASHER NUTS ARMATURE THRUST WASHER END CAP ENGAGING NUT 1 CHARGING CIRCUIT When a conductor (alternating coils) cuts the magnetic field generated by the magnets in the flywheel, a current will be induced in the alternator coil. The permanent magnets in the flywheel have a magnetic field in which the lines of magnetic force run from the North Pole to the South Pole. As the flywheel rotates and the position of the magnets change, the direction of the magnetic field changes or alternates. The alternating coils are wound in different directions to allow current to flow as an A.C. waveform (diag. 2). ROTATION OF FLYWHEEL 2 42
CONVERTING ALTERNATING CURRENT TO DIRECT CURRENT ANODE CATHODE In order to charge a battery, it is necessary to convert alternating current (A.C.) to direct current (D.C.). This is accomplished by using a diode or rectifier (diag. 3). A single diode makes use of only one half of the A.C. signal and is known as HALF WAVE RECTIFICATION (diag. 4). This is acceptable in certain applications. In certain situations it is necessary to make use of the entire A.C. signal. To accomplish this, multiple diodes in a bridge configuration are used to produce FULL WAVE RECTIFICATION (diag. 5). DIRECTION OR FLOW OF CURRENT BAND OR OTHER MARKING INDICATES CATHODE END 3 Current flows through a diode when the anode is more positive than the cathode. The cathode end of the diode should point toward the battery when diode is used between a charging system and a battery. HALF WAVE RECTIFIER SINGLE DIODE The single diode allows only the positive half of the A.C. signal through. It does not allow the negative portion through. + VOLTAGE HALF WAVE RECTIFIER (SINGLE DIODE) + VOLTAGE - VOLTAGE A.C. INPUT - VOLTAGE D.C. OUTPUT 4 FULL WAVE RECTIFIER (BRIDGE RECTIFIER) + VOLTAGE FULL WAVE RECTIFIER (BRIDGE RECTIFIER) The full wave rectifier makes use of the entire A.C. signal, converting it to D.C. - VOLTAGE A.C. INPUT COMPONENTS BATTERY A.C. INPUT + VOLTAGE (D.C.) The batteries used in conjunction with Tecumseh engines are 12 volt lead acid or “maintenance free” style. The chemical energy produced by the dissimilar metals of the battery plates provides a electrical potential that is used to power the electric starter or unit accessories. Consult the original equipment manufacturer’s service manual for battery size, capacities, and testing procedure. + VOLTAGE - VOLTAGE D.C. OUTPUT 5 WIRING The wires used in Tecumseh electrical systems are copper stranded with an insulated coating around the copper strands. CONDITION: All wiring must be fully insulated between connection points, securely fastened and free of foreign material (such as rust and corrosion) at the connection points. This is especially important in the use of batteries where much of the potential may be lost due to loose connections or corrosion. Remember to check the insulation on the wire. All it takes is a pin hole to "ground out" on the engine or frame. This is of special concern when moisture or water is present. This may cause the engine to run erratically or be impossible to start. 43
Page 1 and 2: TECUMSEH T E C H N I C I A N ' S H
Page 3 and 4: GOVERNOR GEAR AND SHAFT SERVICE....
Page 5 and 6: CHAPTER 1 GENERAL INFORMATION ENGIN
Page 7 and 8: ENGINE OIL Use a clean, high qualit
Page 9 and 10: GENERAL INFORMATION CHAPTER 2 AIR C
Page 11 and 12: CHAPTER 3 CARBURETORS AND FUEL SYST
Page 13 and 14: IMPULSE FUEL PUMPS Impulse fuel pum
Page 15 and 16: CARBURETOR IDENTIFICATION Tecumseh
Page 17 and 18: ENGINE TROUBLESHOOTING Engine Will
Page 19 and 20: TESTING 1. After repeated efforts t
Page 21 and 22: DISASSEMBLY PROCEDURE NOTE: Engines
Page 23 and 24: Diaphragm Carburetors 1. Remove the
Page 25 and 26: ASSEMBLY Welch Plugs To install a n
Page 27 and 28: 4. Install the hinge pin from the o
Page 29 and 30: Throttle Lever Remove the throttle
Page 31 and 32: ENGINE OVERSPEEDING 1. If the engin
Page 33 and 34: SPEED CONTROLS AND LINKAGE Many dif
Page 35 and 36: HORIZONTAL SHAFT ENGINES IDLE SPEED
Page 37 and 38: VERTICAL SHAFT ENGINES HIGH SPEED A
Page 39 and 40: GENERAL INFORMATION CHAPTER 5 REWIN
Page 41 and 42: CAUTION: THIS REWIND SPRING IS NOT
Page 43 and 44: 2. Place the pulley assembly into t
Page 45: at the outer edge against the gear
Page 49 and 50: BASIC CHECKS Before going into exte
Page 51 and 52: TROUBLESHOOTING ELECTRICAL CHARGING
Page 53 and 54: 18 Watt A.C. Lighting Alternator Mo
Page 55 and 56: NOTE: ON OLDER POINT IGNITION SYSTE
Page 57 and 58: 5 Amp Alternator System Regulator-R
Page 59 and 60: 7 Amp Alternator System Regulator-
Page 61 and 62: SERVICE This section covers the ser
Page 63 and 64: CHAPTER 7 FLYWHEEL BRAKE SYSTEMS GE
Page 65 and 66: SERVICE If the brake system fails t
Page 67 and 68: CHAPTER 8 IGNITION GENERAL INFORMAT
Page 69 and 70: The condenser acts as an electrical
Page 71 and 72: TESTING PROCEDURE 1. Check for spar
Page 73 and 74: Begin the procedure by replacing th
Page 75 and 76: Other Solid State Systems The follo
Page 77 and 78: LUBRICATION SYSTEMS The lubrication
Page 79 and 80: ENGINE OPERATION PROBLEMS ENGINE KN
Page 81 and 82: TESTING ENGINE KNOCKS 1. Check the
Page 83 and 84: 5. Check the engine valve lash. Res
Page 85 and 86: CYLINDERS Visually check the cylind
Page 87 and 88: Use a ring expander to remove and r
Page 89 and 90: VALVES The valves should be checked
Page 91 and 92: Late production top mounted breathe
Page 93 and 94: COUNTERBALANCE SERVICE To correctly
Page 95 and 96: FOUR CYCLE TORQUE SPECIFICATIONS Th
Page 97 and 98:
ENGINE SPECIFICATIONS STANDARD POIN
Page 99 and 100:
ENGINE SPECIFICATIONS STANDARD POIN
Page 101 and 102:
SOLID STATE AND EXTERNAL IGNITION A
Page 103 and 104:
SOLID STATE AND EXTERNAL IGNITION A
Page 105 and 106:
SOLID STATE AND EXTERNAL IGNITION (
Page 107 and 108:
OIL SEAL DRIVER FLYWHEEL KNOCK-OFF
Page 109 and 110:
DECIMAL/FRACTION CONVERSIONS .016 =
Page 111 and 112:
SEARS CRAFTSMAN CROSS REFERENCE CHA
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3to 11hp 4-cycle l-head engines - Small Engine Suppliers

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