Kohler CH18 Service Manual
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Kohler CH18 Service Manual

Kohler CH18 Service Manual

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CH18-CH25, CH620-CH730, CH740, CH750
Service Manual
IMPORTANT:
Read all safety precautions and instructions carefully before operating equipment. Refer to operating
instruction of equipment that this engine powers.
Ensure engine is stopped and level before performing any maintenance or service.
2
Safety
3
Maintenance
5
Specifi cations
15
Tools and Aids
18
Troubleshooting
23
Air Cleaner/Intake
24
Fuel System
40
Governor System
58
Lubrication System
60
Electrical System
79
Starter System
88
Clutch
90
Disassembly/Inspection and Service
107
Reassembly
24 690 06 Rev. P
KohlerEngines.com
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Summary of Contents for Kohler CH18

  • Page 1 CH18-CH25, CH620-CH730, CH740, CH750 Service Manual IMPORTANT: Read all safety precautions and instructions carefully before operating equipment. Refer to operating instruction of equipment that this engine powers. Ensure engine is stopped and level before performing any maintenance or service. Safety Maintenance Specifi...

  • Page 2: Safety Precautions

    Safety SAFETY PRECAUTIONS WARNING: A hazard that could result in death, serious injury, or substantial property damage. CAUTION: A hazard that could result in minor personal injury or property damage. NOTE: is used to notify people of important installation, operation, or maintenance information. CAUTION WARNING WARNING...

  • Page 3: Maintenance Instructions

    PRO oil and PRO fi lter. ® REPAIRS/SERVICE PARTS Kohler genuine service parts can be purchased from Kohler authorized dealers. To fi nd a local Kohler authorized dealer visit KohlerEngines.com or call 1-800-544-2444 (U.S. and Canada). 24 690 06 Rev. P...

  • Page 4: Oil Recommendations

    KOHLER PRO Extended Life Oil Filter. Alternative full-synthetic oil). Remove spark plug(s) and pour engine oils and oil fi lters may be used with KOHLER about 1 oz. of engine oil into cylinder(s). Replace engines but require 100-Hour oil and 200-Hour oil fi lter spark plug(s) and crank engine slowly to distribute change intervals for proper maintenance.

  • Page 5: Specifications

    Specifi cations Engine Dimensions with Low-Profi le Air Cleaner Dimensions in millimeters. Inch equivalents shown in [ ]. 24 690 06 Rev. P KohlerEngines.com...
  • Page 6 Specifi cations Engine Dimensions with Heavy-Duty Air Cleaner Dimensions in millimeters. Inch equivalents shown in [ ]. 135.00 424.61 130.00 285.90 304.48 [5.315] [16.717] [5.118] [11.256] [11.987] 50.85 AIR FILTER RAIN 272.17 AIR FILTER COVER 93.33 [2.002] CAP REMOVAL ASSEMBLY REMOVAL [3.674] [10.715] 414.17...

  • Page 7: Engine Identification Numbers

    Lubricate threads with engine oil prior to assembly. Any and all horsepower (hp) references by Kohler are Certifi ed Power Ratings and per SAE J1940 & J1995 hp standards. Details on Certifi ed Power Ratings can be found at KohlerEngines.com.
  • Page 8 Specifi cations CH18/CH20/ CH22/CH23/ CH22/ CH620 CH25/ CH620/CH621/ CH640 CH730/ TORQUE SPECIFICATIONS CH640/CH641 CH670/CH680 CH740 CH750 Closure Plate Fastener 24.4 N·m (216 in. lb.) Connecting Rod Cap Fastener (torque in increments) 8 mm straight shank 22.7 N·m (200 in. lb.) 8 mm step-down 14.7 N·m (130 in.

  • Page 9: Clearance Specifications

    Specifi cations CH18/CH20/ CH22/CH23/ CH22/ CH620 CH25/ CH620/CH621/ CH640 CH730/ TORQUE SPECIFICATIONS CH640/CH641 CH670/CH680 CH740 CH750 Solenoid (Starter) Mounting Hardware Nippondenso Starter 6.0-9.0 N·m (53-79 in. lb.) Delco-Remy Starter 4.0-6.0 N·m (35-53 in. lb.) Nut, Positive (+) Brush Lead Nippondenso Starter 8.0-12.0 N·m (71-106 in.
  • Page 10 Specifi cations CH18/CH20/ CH22/CH23/ CH22/ CH620 CH25/ CH620/CH621/ CH640 CH730/ CLEARANCE SPECIFICATIONS CH640/CH641 CH670/CH680 CH740 CH750 Connecting Rod Connecting Rod-to-Crankpin Running Clearance 0.030/0.055 mm (0.0012/0.0022 in.) Max. Wear Limit 0.070 mm (0.0028 in.) Connecting Rod-to-Crankpin Side Clearance 0.26/0.63 mm (0.0102/0.0248 in.) Connecting Rod-to-Piston Pin Running Clearance 0.015/0.028 mm (0.0006/0.0011 in.)
  • Page 11 Specifi cations CH18/CH20/ CH22/CH23/ CH22/ CH620 CH25/ CH620/CH621/ CH640 CH730/ CLEARANCE SPECIFICATIONS CH640/CH641 CH670/CH680 CH740 CH750 Cylinder Bore Bore I.D. 77.000/ 80.000/ 82.988/83.013 mm 77.025 mm 80.025 mm (3.2672/3.2682 in.) (3.0315/ (3.1496/ 3.0325 in.) 3.1506 in.) Max. Wear Limit 77.063 mm 80.065 mm...
  • Page 12 Specifi cations CH18/CH20/ CH22/CH23/ CH22/ CH620 CH25/ CH620/CH621/ CH640 CH730/ CLEARANCE SPECIFICATIONS CH640/CH641 CH670/CH680 CH740 CH750 Piston, Piston Rings, and Piston Pin (Style A continued) Middle Compression Ring-to-Groove Side Clearance 0.040/ 0.030/ 0.015/0.037 mm 0.080 mm 0.076 mm (0.0006/0.0015 in.) (0.0016/...
  • Page 13 Specifi cations CH18/CH20/ CH22/CH23/ CH22/ CH620 CH25/ CH620/CH621/ CH640 CH730/ CLEARANCE SPECIFICATIONS CH640/CH641 CH670/CH680 CH740 CH750 Piston, Piston Rings, and Piston Pin (Style B continued) Middle Compression Ring End Gap New Bore 1.400/ 1.519/1.797 mm 1.679 mm (0.0598/0.0708 in.) (0.0551/ 0.0661 in.)

  • Page 14: General Torque Values

    Specifi cations GENERAL TORQUE VALUES English Fastener Torque Recommendations for Standard Applications Bolts, Screws, Nuts and Fasteners Assembled Into Cast Iron or Steel Grade 2 or 5 Fasteners Into Aluminum Size Grade 2 Grade 5 Grade 8 Tightening Torque: N·m (in. lb.) ± 20% 8-32 2.3 (20) 2.8 (25)

  • Page 15: Tools And Aids

    Shrader Valve Adapter Hose DTI-037 Wire Probe Set (2 pieces regular wire with clip; 1 piece fused wire) DTI-031 Hose Removal Tool, Dual Size/End (also sold as individual Kohler tool) DTI-033 K-Line Adapter Jumper Lead Wiring Harness Kohler 25 176 23-S...
  • Page 16 For reaming worn valve guides to accept replacement oversize valves. Can be used in low-speed drill press or with handle below for hand reaming. Reamer Handle Design Technology Inc. For hand reaming using Kohler 25 455 12-S reamer. DTI-K830 AIDS Description Source/Part No.
  • Page 17 Tools and Aids FLYWHEEL HOLDING TOOL ROCKER ARM/CRANKSHAFT TOOL A fl ywheel holding tool can be made out of an old junk A spanner wrench to lift rocker arms or turn crankshaft fl ywheel ring gear and used in place of a strap wrench. may be made out of an old junk connecting rod.

  • Page 18: Troubleshooting Guide

    Troubleshooting TROUBLESHOOTING GUIDE When troubles occur, be sure to check simple causes which, at fi rst, may seem too obvious to be considered. For example, a starting problem could be caused by an empty fuel tank. Some general common causes of engine troubles are listed below and vary by engine specifi cation. Use these to locate causing factors.
  • Page 19 Troubleshooting EXTERNAL ENGINE INSPECTION Engine Loses Power NOTE: It is good practice to drain oil at a location away ● Dirty air cleaner element. from workbench. Be sure to allow ample time for ● Engine overheated. complete drainage. ● Excessive engine load. ●...

  • Page 20: Crankcase Vacuum Test

    Troubleshooting CRANKCASE VACUUM TEST WARNING WARNING Carbon Monoxide can cause severe nausea, Rotating Parts can cause severe injury. fainting or death. Stay away while engine is in operation. Avoid inhaling exhaust fumes. Never run engine indoors or in enclosed spaces. Keep hands, feet, hair, and clothing away from all Engine exhaust gases contain poisonous carbon moving parts to prevent injury.

  • Page 21: Compression Test

    Troubleshooting COMPRESSION TEST A compression test is best performed on a warm engine. Clean any dirt or debris away from base of spark plug(s) before removing them. Be sure battery is fully charged, choke is off , and throttle is wide open during test. Compression should be at least 160 psi and should not vary more than 15% between cylinders.
  • Page 22 Troubleshooting Test Pressure Chart for Dual Gauge Tool Left Gauge Regulated Pressure Selection Right Gauge Reading in PSI 80 PSI Recommended for engines over 200 cc or those exhibiting high leakage at 35 PSI setting. 35 PSI Recommended for single cylinder 31.5 24.5 17.5...

  • Page 23: Air Cleaner/Intake

    Air Cleaner/Intake AIR CLEANER NOTE: Operating engine with loose or damaged air cleaner components could cause premature These systems are CARB/EPA certifi ed and components wear and failure. Replace all bent or damaged should not be altered or modifi ed in any way. components.

  • Page 24: Fuel Pump

    fi tting on crankcase or valve cover. Low permeation fuel line must be installed on carbureted Kohler Co. engines to maintain EPA and CARB 4. Attach new fuel pump using screws. Torque screws regulatory compliance.
  • Page 25 Fuel System CARBURETORS Gasoline is extremely fl ammable and its vapors can WARNING explode if ignited. Store gasoline only in approved Explosive Fuel can cause fi res and severe containers, in well ventilated, unoccupied buildings, away burns. from sparks or fl ames. Spilled fuel could ignite if it comes in contact with hot parts or sparks from ignition.
  • Page 26 Float Assembly Carburetor Lower Main Jet Body (Throttle) CH18-740 engines in this series are equipped with either a Keihin or Nikki one-barrel fi xed main jet carburetor. Idle Fuel Adjusting Solenoid Seat Most applications use a fuel shut-off solenoid and also Needle contain an accelerator pump.
  • Page 27 Fuel System Troubleshooting Checklist When engine starts hard, runs roughly or stalls at low idle speed, check following areas before adjusting or disassembling carburetor. 1. Make sure fuel tank is fi lled with clean, fresh gasoline. 2. Make sure fuel tank cap vent is not blocked and that it is operating properly. 3.
  • Page 28 Fuel System Keihin Carburetor Fuel Shut-Off Solenoid Carburetor Circuits Most carburetors are equipped with a fuel shut-off Float solenoid. Solenoid is attached to fuel bowl. Solenoid has Fuel level in bowl is maintained by fl oat and fuel inlet a spring-loaded pin that retracts when 12 volts is applied needle.
  • Page 29 Fuel System 2. Release governor lever and check that throttle lever Keihin Carburetor Servicing is in idle position. Turn governed idle adjustment screw to obtain equipment manufacturer’s WARNING recommended idle speed (1500-1800 RPM). Some engines have a bendable tab that is used to set this speed.
  • Page 30 Fuel System 5. Carefully remove main jet(s) from carburetor. For 15. Slide choke shaft and spring into carburetor. Pivot two-barrel carburetors, note and mark jets by (preload) shaft 3/4 turn counterclockwise with inner location for proper reassembly. Main jet(s) may be leg of spring against formed stop within choke lever size/side specifi...
  • Page 31 Fuel System 26. For two-barrel carburetor, correct fl oat height For one-barrel carburetor, correct fl oat height setting is 17 mm (0.669 in.) ± 1.5 mm (0.059 in.), setting is 22 mm (0.86 in.), measured from fl oat measured from fl oat bottom to body of carburetor. bottom to body of carburetor.
  • Page 32 Fuel System 6. If carburetor has a fuel shut-off solenoid, unplug Nikki Carburetor Servicing solenoid lead from solenoid. Use a thin wall wrench to loosen solenoid. Remove solenoid and discard solenoid gasket. WARNING If carburetor doesn't have a fuel shut-off solenoid, remove plug and discard gasket.
  • Page 33 To obtain high altitude carburetor kit 20. Correct fl oat height setting is 3 mm (0.118 in.), information or to fi nd a Kohler authorized dealer, visit measured from body of carburetor to top of fl oat.
  • Page 34 Calculations and unique software routines developed specifi cally for this Kohler engine operate a carburetor choke lever through an assembly (bracket, linkage) to control a rotary stepper motor. Power and ground are supplied to master CDI &...
  • Page 35 Fuel System eChoke Components ™ Stepper Motor Keihin Carburetor Rotary Stepper Motor Rivet Bracket Stepper Motor Stepper Motor Lever Bushing Screw Linkage Set Screw Speed Control Spring Idle Adjustment Cable Ball Screw Ball Joint Cup Governor Linkage Screw Lever Adapter Stepper Motor Lever Screw Nikki Carburetor...
  • Page 36 Fuel System attempt to run through a normal start/crank/run/off eChoke System Standard Checks sequence and monitor blink codes to determine if ™ controller operation is correct. Both normal operation and error code indication is listed in blink code table that follows (on next page). Note that code changes for each level of operation.
  • Page 37 Fuel System Blink Codes NOTE: Use of any other type of lamp, other than LED, could damage components. Table shows both normal operation and failure mode blinks codes. Normal operation blink codes will be displayed when no failure modes are detected during operation. These codes will only appear if there is no captured failure blink code.
  • Page 38 Fuel System Troubleshooting eChoke Related Causes ™ Condition Possible Cause Conclusion Engine starts hard, runs rough, or Choke not closing/moving Stepper motor/bracket/link assembly stalls at idle speed. a. Broken or missing link. must allow for full travel, make sure link is located properly and connected.
  • Page 39 Fuel System Replace Rotary Stepper Motor 4. Position new rotary stepper motor on bracket with leads down, insert rivet (as shown) and use rivet tool to pull rivet until tight. Install second rivet to secure motor to bracket. 5. Position rotary stepper motor/bracket/rivet assembly on carburetor and reinstall lever on motor.

  • Page 40: Governor System

    Governor System GOVERNOR These engines are equipped with an electronic governor or a mechanical governor. ELECTRONIC GOVERNOR Digital Linear Actuator (DLA) Energizing bi-directional digital linear actuator coils in Electronic Governor System proper sequence, causes threaded shaft to move out Engines with electronic governor are equipped with of, or back into rotor, in precise linear increments.
  • Page 41 Governor System Adjustment Troubleshooting DLA Details Engine Starts But Will Not Continue to Run 1. Check linkage connection between DLA and throttle plate. 2. Verify throttle plate is opened during start procedure. Engine is unlikely to start if throttle plate is not opened.
  • Page 42 Governor System Ohms Tests GCU/Harness Diagnostics and Troubleshooting 1. Remove GCU and unplug wiring harness. NOTE: It is important to use proper sized probes to These two tests are for measuring resistance of DLA perform these tests. Probes that are incorrect circuit that sends a signal to GCU.
  • Page 43 Governor System Speed Control Input GCU Designs Red Wire with Yellow Tracer. This connection is either a single wire red with yellow tracer or a 6 pin connector body with a red wire with yellow tracer. First Design GCU Second Design GCU Green LED Light Yellow LED Light F Fourth (Latest) Design...
  • Page 44 Governor System Several diff erent GCU designs have been used. First design (24 584 40-S and earlier) had a black potting compound, did not have LED lights, and did not store diagnostic trouble codes. See page 42 for troubleshooting detail and a basic electrical diagram for this GCU design. See pages 50-52 for a troubleshooting fl...
  • Page 45 Governor System FIRST DESIGN GCU Troubleshooting Electronic Governor Failure Condition Possible Causes Equipment Observations Inspection/Testing Target/Selected Loss of GCU power When connection is lost, no DLA Test GCU power (red/B+) Speed not (B+ or Ground). movement will be seen. When wire for supply voltage and Maintained (Potentially...
  • Page 46 Governor System SECOND DESIGN GCU Troubleshooting Electronic Governor Failure Condition Possible Causes Equipment Observations Inspection/Testing Target/Selected Loss of GCU power When connection is lost, no DLA Test for GCU power by Speed not (B+ or Ground). movement will be seen. When turning key to ON position Maintained (Potentially...
  • Page 47 Governor System SECOND DESIGN GCU Blink Codes LED Diagnostics Response Failure Condition Possible Causes Response Time Yellow LED Green LED Overspeed (Over External noise on ignition input Ground to kill, Flashing 4500 RPM for 0.5 close carb throttle seconds Frozen carb throttle plate seconds sustained) plate DLA failure...
  • Page 48 Governor System SECOND DESIGN GCU Basic Electrical Diagram of Electronic Governor System Kill Tab (Speed Signal) Speed Signal Power Green LED Light Yellow LED Light Device Ground Ignition Module DLA Driver Controls Application Supplied Speed Control Input Operation Input Voltage: 0-1 Volts at Idle/9+ Volts at High Speed.
  • Page 49 Governor System THIRD AND FOURTH DESIGN GCU Troubleshooting Electronic Governor Failure Condition Possible Causes Equipment Observations Inspection/Testing Target/Selected Loss of GCU power When connection is lost, no DLA Test for GCU power by Speed not (B+ or Ground). movement will be seen. When turning key to ON position Maintained (Potentially...
  • Page 50 Governor System THIRD AND FOURTH DESIGN GCU Blink Codes for Software Running Codes - Activated when engine is running. LED Diagnostics Response Failure Condition Possible Causes Response Time Yellow LED Green LED Running Normally None BLINKS BLINKS RPM Too High Mechanical bindage None BLINKS...
  • Page 51 Governor System THIRD DESIGN GCU Basic Electrical Diagram of Electronic Governor System Kill Tab (Speed Signal) Speed Signal Power Green LED Light Yellow LED Light Device Ground Ignition Module DLA Driver Controls Application Supplied Speed Control Input Operation Input Voltage: 0-1 Volts at Idle/9+ Volts at High Speed.
  • Page 52 Governor System FOURTH (LATEST) DESIGN GCU Basic Electrical Diagram of Electronic Governor System Kill Tab (Speed Signal) Power Speed Signal Green LED Light Yellow LED Light Ignition Module Device Ground DLA Driver Controls Application Supplied Speed Control Input Operation Input Voltage: 0-1 Volts at Idle/9+ Volts at High Speed.
  • Page 53 Governor System Electronic Governor Troubleshooting Flow Chart Turn off key switch. Do Not Touch Digital Linear Actuator (DLA) NOTE: DLA is not a solenoid. It is a precision electronic motor. Do not exert force to center clevis shaft! Visually inspect DLA and Linkage. See illustrations on pages 37 and 38. Confi...
  • Page 54 Engine speed increases Operation Input Voltage: (if it was at low speed). 0-1 Volts at Idle/9+ Volts at High Speed. Kohler electronic governor system tests OK. Test Fail Pass control system of equipment. Refer to Equipment Manufacturer’s diagnostic procedures for control system.
  • Page 55 Governor System Electronic Governor Troubleshooting Flow Chart (Continued) Inspect wiring harness for broken wire or bad connections. (Repair/Replace as required). Test supply ground circuit to GCU using a continuity OHM/tester. Refer to page 39. Test supply voltage to GCU using volt meter. Refer to page 39 (battery voltage +/- 1 volt) Note: Prevent Damage to Connector.

  • Page 56: Mechanical Governor

    Governor System MECHANICAL GOVERNOR A centrifugal fl yweight mechanical governor is designed to hold engine speed constant under changing load conditions. Governor gear/fl yweight mechanism is mounted inside crankcase on closure plate, and is driven off gear on camshaft. Governor Components H Inside Engine Throttle Lever Throttle Linkage...
  • Page 57 Governor System Sensitivity Adjustment Governor sensitivity is adjusted by repositioning governor spring in holes of governor lever. If speed surging occurs with a change in engine load, governor is set too sensitive. If a big drop in speed occurs when normal load is applied, governor should be set for greater sensitivity and adjust as follows: 1.

  • Page 58: Lubrication System

    Lubrication System This engine uses a full pressure lubrication system which 3. If oil is low on indicator, add oil up to top of indicator delivers oil under pressure to crankshaft, camshaft, mark. connecting rod bearing surfaces, and hydraulic valve 4.
  • Page 59 Lubrication System OIL SENTRY (if equipped) ™ This switch is designed to prevent engine from starting in a low oil or no oil condition. Oil Sentry may not shut ™ down a running engine before damage occurs. In some applications this switch may activate a warning signal. Read your equipment manuals for more information.

  • Page 60: Electrical System

    Electrical System SPARK PLUGS Inspection Inspect each spark plug as it is removed from cylinder CAUTION head. Deposits on tip are an indication of general Electrical Shock can cause injury. condition of piston rings, valves, and carburetor. Do not touch wires while engine is running. Normal and fouled plugs are shown in following photos: Normal Spark Plug Component and Details...
  • Page 61 Electrical System Carbon Fouled BATTERY A 12-volt battery with 400 cold cranking amps (cca) is generally recommended for starting in all conditions. A smaller capacity battery is often suffi cient if an application is started only in warmer temperatures. Refer to following table for minimum capacities based on anticipated ambient temperatures.
  • Page 62 Electrical System ELECTRONIC IGNITION SYSTEMS CDI/MDI Ignition Module Identifi cation Ignition System Components CDI Ignition Module MDI Ignition Module These systems use a capacitive discharge (CD) coil. Kill Switch/ With CDI fi xed timing, ignition timing and spark remains Off Position of Air Gap constant regardless of engine speed.
  • Page 63 Electrical System Wiring Diagram-15/20/25 Amp Regulated Battery Charging System with CDI/MDI 24 690 06 Rev. P KohlerEngines.com...
  • Page 64 Electrical System Spark Plug(s) Oil Pressure Switch Oil Sentry (Green) White Kill ™ Flywheel Stator Rectifi er-Regulator Ignition Module CDI/MDI Ignition Assembly Connector Solenoid Shift Starter Rectifi er-Regulator Oil Sentry Kill (Green) Violet B+ Assembly ™ Starter Solenoid Tang Starter Solenoid Stud Fuse Blue Alternate Ignition Kill...
  • Page 65 Electrical System Test Ignition Systems NOTE: If engine starts or runs during testing, you may need to ground kill lead to shut it down. Because you have interrupted kill circuit, it may not stop using switch. Isolate and verify trouble is within engine. 1.
  • Page 66 Electrical System Wiring Diagram-15/20/25 Amp Regulated Battery Charging System with Variable Ignition Timing SMART- SPARK ™ KohlerEngines.com 24 690 06 Rev. P...
  • Page 67 Electrical System Oil Pressure Switch Oil Sentry (Green) Spark Plug(s) Kill ™ Flywheel Stator 22, 25 HP Smart- Trigger Ignition Module Assembly Spark Ignition ™ Yellow on Analog Module Speed Brown Yellow SAMs Pink on Digital Advance 22, 25 HP SAMs Rectifi...
  • Page 68 Electrical System Condition Possible Cause Conclusion Both cylinders have good spark but Spark Plug(s) Install new spark plug(s) and retest engine runs poorly or existing plug engine performance. condition is questionable. If problem persists, check for timing advance. 1 cylinder has good spark and other Ignition Test ignition modules and cylinder has no or intermittent spark.
  • Page 69 Electrical System Test Smart-Spark Ignition Modules and Smart-Spark Ignition Module Resistance Table ™ ™ Connections 24 584 03 24 584 15-S NOTE: Resistance values apply only to modules that have been on a running engine. New service 24 584 11 24 584 36-S modules may have higher resistance until they (1 11/16 in.
  • Page 70 Electrical System 6. Reattach lead wires to ignition module(s), noting if resistance is felt, indicating a snug fi t between male and female terminals. If any connections do not feel snug, disconnect lead, lightly pinch female terminal with a pliers, and recheck fi...
  • Page 71 Electrical System To replace battery, remove outer set of screws on 1. Check SAM part number stamped on end of faceplate and carefully lift panel from body. Unplug housing. connector and pull battery (with mounting tape) off back a. If it is an ASAM (24 584 09 or 24 584 10), of tester.
  • Page 72 Electrical System Wiring Diagram-15/20/25 Amp Regulated Battery Charging System with DSAI Ignition and Key Switch KohlerEngines.com 24 690 06 Rev. P...
  • Page 73 Electrical System Black (Ground) Intake Green (Oil Sentry Oil Pressure Switch Manifold Mounting Black ™ Pulse Signal Lead) Screw White Spark Plug(s) Black (Ground) Flywheel Stator Red (B+) White (DSAI Kill) Module Screw Assembly White (AC Charging Rectifi er-Regulator DSAI Module Rectifi...
  • Page 74 Electrical System Condition Possible Cause Conclusion Both cylinders have good spark but Spark Plug(s) Install new spark plug(s) and retest engine runs poorly or existing plug engine performance. condition is questionable. If problem persists, check for?? 1 cylinder has good spark and other Ignition Test ignition modules and cylinder has no or intermittent spark.

  • Page 75: Battery Charging System

    Electrical System BATTERY CHARGING SYSTEM NOTE: Observe following guidelines to avoid damage to electrical system and components: ● Make sure battery polarity is correct. A negative (–) ground system is used. ● Disconnect rectifi er-regulator plug and/or wiring harness plug before doing any electric welding on equipment powered by engine.
  • Page 76 Electrical System 15/20/25 Amp Battery Charging Systems NOTE: Always zero digital volt-ohm meter (DVOM) on each scale before testing to ensure accurate readings. Voltage test should be made with engine running at specifi c test condition noted. Battery should be checked for state of charge (non-operating voltage 12.5 VDC or lower, battery should be charged or replaced).
  • Page 77 Electrical System Wiring Diagram-3 Amp Unregulated Battery Charging System/70 Watt Lighting Optional Oil Optional Oil Ground-To-Kill Sentry Switch Sentry Switch 12 V. Battery Light Lead (White) ™ ™ (Shutdown) (Indicator Light) Optional Ground Optional Fuse Key Switch Ammeter Blue Solenoid Lights Starter Yellow...
  • Page 78 Electrical System 3 Amp/70 Watt Lighting Stator NOTE: Always zero ohmmeter on each scale before testing to ensure accurate readings. Voltage tests should be made with engine running at 3600 RPM with no load. Battery must be good and fully charged. To test charging system for no charge to battery: To test charging system for no lights: 1.

  • Page 79: Starter System

    Starter System NOTE: Do not crank engine continuously for more than 10 seconds. Allow a 60 second cool down period between starting attempts. Failure to follow these guidelines can burn out starter motor. NOTE: If engine develops suffi cient speed to disengage starter but does not keep running (a false start), engine rotation must be allowed to come to a complete stop before attempting to restart engine.
  • Page 80 4. Clean splines on drive shaft thoroughly with solvent. Dry splines thoroughly. 5. Apply a small amount of Kohler electric starter drive lubricant, to splines. Use of other lubricants may cause drive pinion to stick or bind.
  • Page 81 A brush holder tool can easily be made 5. Install thru bolts and tighten securely. from thin sheet metal. 6. Lubricate drive shaft with Kohler starter drive 1. Remove brush springs from pockets in brush holder. lubricant. Install drive components following 2.
  • Page 82 Starter System SOLENOID SHIFT ELECTRIC STARTERS Nippondenso Starters Solenoid Shift Starter Components Starter Disassembly NOTE: When removing lever and armature be careful not to lose thrust washer. 1. Disconnect lead wire from solenoid. 2. Remove nuts securing solenoid, and remove solenoid from starter assembly.
  • Page 83 Brush Replacement 4 brushes and springs are serviced as a set. Use a new Kohler brush and spring kit if replacement is necessary. 1. Perform steps 1-5 in Starter Disassembly. 2. Remove screws securing brush holder assembly to end cap (plate).
  • Page 84 Starter System 10. Starter reassembly when replacing brushes/brush Starter Reassembly holder assembly: NOTE: Always use a new retainer. Do not reuse old a. Hold starter assembly vertically on end housing, retainers that have been removed. and carefully position assembled brush holder NOTE: Correctly installed, center pivot section of drive assembly, with supplied protective tube, against lever will be fl...
  • Page 85 Starter System Solenoid Tests NOTE: DO NOT leave 12 volt test leads connected to solenoid for any time over what is necessary for performing each of individual tests. Internal damage to solenoid may occur. Disconnect all leads from solenoid including positive brush lead attached to lower stud terminal. Remove mounting hardware and separate solenoid from starter for testing.

  • Page 86: Retractable Starters

    Starter System RETRACTABLE STARTERS Remove Starter 1. Remove screws securing starter to blower housing. WARNING 2. Remove starter assembly. Uncoiling Spring can cause severe injury. Rope Replacement Wear safety goggles or face protection when servicing retractable starter. NOTE: Do not allow pulley/spring to unwind. Enlist aid of a helper if necessary.
  • Page 87 Starter System Pawls (dogs) Replacement 1. Install a clamp to hold pulley in starter housing and prevent if from rotating. 2. Remove center screw, washer, and pawl retainer. 3. Note position of pawls and pawl springs before removing. Remove pawls, pawls springs, brake spring and brake washer from pulley.
  • Page 88 Clutch WET DISC TYPE CLUTCH (if equipped) Wet Disc Type Clutch Components Shifting Lever Gasket Seal Shaft (Yoke) Nameplate Clutch Housing Adjusting Ring Driven Member Bearing Release Release Sleeve Pressure Plate Pilot Bearing Assembly Adjusting Lock Clutch Assembly Power Shaft Retaining Rings Yoke Roll Pin...
  • Page 89 Clutch Service 1. Release clutch and remove nameplate. Using a On this clutch type, an oil splash type lubrication system large screwdriver, turn adjusting ring clockwise, one is used. Proper oil level must be maintained to provide notch at a time, until fi rm pressure is required to effi...

  • Page 90: Disassembly/Inspection And Service

    Disassembly/Inspection and Service WARNING Before working on engine or equipment, disable engine as Accidental Starts can cause severe injury or follows: 1) Disconnect spark plug lead(s). 2) Disconnect death. negative (–) battery cable from battery. Disconnect and ground spark plug lead(s) before servicing.
  • Page 91 Disassembly/Inspection and Service Clean all parts thoroughly as engine is disassembled. Heavy-Duty Air Cleaner Only clean parts can be accurately inspected 1. Disconnect breather hose from fi tting in adapter or and gauged for wear or damage. There are many elbow.
  • Page 92 Disassembly/Inspection and Service Remove Control Panel (if equipped) Remove Throttle and Choke Controls (if equipped) 1. Disconnect Oil Sentry indicator light wires. Control Bracket Components (Mechanical ™ Governor) 2. Disconnect choke control cable from control bracket. 3. Disconnect throttle control cable or shaft. 4.
  • Page 93 Disassembly/Inspection and Service Remove Carburetor Remove Oil Sentry (if equipped) ™ 1. Disconnect lead from Oil Sentry switch. ™ WARNING 2. Remove Oil Sentry switch from breather cover. ™ Explosive Fuel can cause fi res and severe burns. Remove Electric Starter Motor Do not fi...
  • Page 94 Disassembly/Inspection and Service Remove Inner Baffl es and Breather Cover Remove Intake Manifold Inner (valley) baffl es are attached at one corner using 1. Remove screws securing intake manifold to cylinder same fasteners as breather cover. heads. Note which screws hold wiring clamps. 1.
  • Page 95 Disassembly/Inspection and Service Remove Valve Covers Disassemble Cylinder Heads Three valve cover designs have been used. Earliest NOTE: These engines use valve stem seals on intake type used a gasket and RTV sealant between cover and valves. Use a new seal whenever valve is sealing surface of cylinder head.

  • Page 96: Exhaust Valve

    Disassembly/Inspection and Service Inspection and Service Valve Details EXHAUST VALVE INTAKE VALVE EXHAUST INSERT INTAKE INSERT Dimension Intake Exhaust Seat Angle 89° 89° Insert O.D. 36.987/37.013 mm (1.4562/1.4572 in.) 32.987/33.013 mm (1.2987/1.2997 in.) Guide Depth 4 mm (0.1575 in.) 6.5 mm (0.2559 in.) Guide I.D.
  • Page 97 0.25 mm oversize stems must then be used. damage. If lifters need to be replaced, apply a liberal If guides are within limits but valve stems are worn coating of Kohler lubricant to base of each new lifter beyond limits, install new valves. before it is installed.
  • Page 98 Use a hook-end tool next to post and pull Inspect ring gear for cracks or damage. Kohler does not outward to separate small metal retainers. Then provide ring gear as a serviceable part. Replace fl ywheel unsnap fan from remaining mounting posts.
  • Page 99 Disassembly/Inspection and Service Crankcase Components Oil Seal Closure Plate (Style A) Gerotor Gear (Style A) Dipstick Tube Oil Pick-Up Tube Oil Pump Assembly Governor Gear Shaft Governor Gear (Style A) (Style A) Camshaft Piston Pin Piston Ring Set Piston Pin Retainer Connecting Rod End Piston (Style B) Connecting Rod...
  • Page 100 Disassembly/Inspection and Service Inspection Governor Gear Assembly Inspect governor gear teeth. Replace gear if it is worn, chipped, or if any teeth are missing. Inspect governor Governor Shaft Component and Details weights. They should move freely in governor gear. Disassembly NOTE: Governor gear is held onto shaft by small molded tabs in gear.
  • Page 101 Disassembly/Inspection and Service Oil Pump Assembly (Style A) Oil Pump Assembly (Style B) Oil pump is mounted inside closure plate. If service is Oil pump is mounted inside closure plate. If service is required, continue with Disassembly, Inspection, and required, continue with Disassembly, Inspection, and Reassembly.
  • Page 102 Disassembly/Inspection and Service Ring failure is usually indicated by excessive oil Remove Connecting Rods with Pistons and Rings consumption and blue exhaust smoke. When rings fail, NOTE: If a carbon ridge is present at top of either oil is allowed to enter combustion chamber where it is cylinder bore, use a ridge reamer tool to remove burned along with fuel.
  • Page 103 Disassembly/Inspection and Service Piston Style B Install New Piston Rings 1. Cylinder bore must be de-glazed before service ring Piston Ring Orientation sets are used. 2. If cylinder bore does not need re-boring and if old piston is within wear limits and free of score or scuff marks, old piston may be reused.
  • Page 104 Disassembly/Inspection and Service Carefully pull crankshaft from crankcase. Note thrust Connecting Rods washers and shims if used. Off set, stepped-cap connecting rods are used in all Inspect gear teeth of crankshaft. If teeth are badly worn, these engines. chipped, or some are missing, replacement of crankshaft Inspection and Service will be necessary.
  • Page 105 Apply a light coat of P80 Emulsion Lubricant (refer to Tools and Aids) to outside diameter of oil seal. NOTE: Kohler pistons are custom-machined to exacting Install new seal to depth shown using a seal installer. tolerances. When oversizing a cylinder, it should be machined exactly 0.25 mm (0.010 in.) or 0.50...
  • Page 106 Style B Model Dimension A Dimension B CH18/CH20/ CH22/ 6 mm (0.2362 in.) CH620/CH621/ CH640/CH641 CH22/CH23/ CH670/CH680 6 mm (0.2362 in.) 13 mm (0.5118 in.) CH620 674cc 13 mm (0.5118 in.)
  • Page 107 Reassembly Crankcase Components Oil Seal Closure Plate (Style A) Gerotor Gear (Style A) Dipstick Tube Oil Pick-Up Tube Oil Pump Assembly Governor Gear Shaft Governor Gear (Style A) (Style A) Camshaft Piston Pin Piston Ring Set Piston Pin Retainer Connecting Rod End Piston (Style B) Connecting Rod Crankshaft...
  • Page 108 Reassembly NOTE: Cylinders are numbered on crankcase. Make Install Governor Cross Shaft sure to install piston, connecting rod and end 1. Lubricate governor cross shaft bearing surfaces in cap into its appropriate cylinder bore as crankcase with engine oil. previously marked at disassembly. Do not mix end caps and connecting rods.
  • Page 109 Reassembly Determining Camshaft End Play Thrust Bearing, Washer and Shim 1. Install shim removed during disassembly onto Thrust Bearing, Washer, and Shim Sequence camshaft. 2. Position camshaft end play checking tool on camshaft. 3. Apply pressure on camshaft end play checking tool (pushing camshaft toward crankshaft).
  • Page 110 Reassembly Remove closure plate. If end play requires adjustment, Install Closure Plate Assembly remove original spacer and install appropriate size shim spacer in its place. Then follow procedure under Install Sealant Pattern and Torque Sequence Closure Plate Assembly. Install Closure Plate Oil Seal Oil Seal Depth RTV sealant is used as a gasket between closure plate and crankcase.
  • Page 111 Reassembly Flywheel/Ignition Components Debris Screen Flywheel Screw Washer Flywheel Magnet Stator Ignition Module Backing Plate Woodruff Key Spring Washer Spacer Metal Debris Screen Ring Support Metal Debris Screen Washer Assembly NOTE: Make sure fl ywheel key is installed properly in Install Stator and Backing Plates keyway.
  • Page 112 Reassembly Install Plastic Debris Screen Install Supports for Metal Debris Screen 1. If a metal debris screen is used, with threaded CAUTION individual supports, install a spacer washer on external threads. Apply Loctite (removable) ® ® Failure to utilize or reassemble debris screen onto threads.
  • Page 113 Reassembly b. Thread opposite end of stud with preapplied Assemble Cylinder Heads locking compound into crankcase until specifi ed Prior to installation, lubricate all components with engine height from crankcase surface is achieved. oil, paying particular attention to lip of valve stem seal, When threading in studs, use a steady tightening valve stems and valve guides.
  • Page 114 Reassembly Install Spark Plugs Install Intake Manifold 1. Check gap using wire feeler gauge. Adjust gap to Torque Sequence 0.76 mm (0.030 in.). 2. Install plug into cylinder head. 3. Torque plug to 27 N·m (20 ft. lb.). Install Ignition Modules 1.
  • Page 115 Reassembly External Engine Components Intake Manifold Gasket Carburetor Outer Baffl e Breather Tube Oil Sentry Breather Cover Breather Gasket ™ Inner Baffl e Breather Reed Filter Electric Starter Lifting Bracket Fixed Guard Blower Housing Debris Shield Wire Clip Oil fi lter Nipple Oil Cooler Valve Cover Fuel...
  • Page 116 Reassembly 3. Position outer baffl es and loosely start mounting Install Breather Cover and Inner Baffl es screws. M6 screws go into back of cylinders. Short Breather Cover Torque Sequence M5 screws go into lower holes closest to blower housing. Short screw on oil fi lter side is also used to mount wire harness clip.
  • Page 117 Reassembly One-Barrel Nikki Carburetor Models Install Fuel Pump 1. Install a new carburetor gasket. Make sure all holes align and are open. WARNING 2. If mechanical governor, install carburetor and control Explosive Fuel can cause fi res and severe assembly, throttle linkage and governor lever as an burns.
  • Page 118 Reassembly Control Bracket Components (Mechanical KEIHIN CARBURETOR Governor) Governor Lever and Spring Details Governor Lever Hole Position (6 mm) Governor Lever Governed Idle Hole Hole 1 Hole 2 Hole 3 Hole 4 Hole 5 Hole 6 6 mm Governor Lever and Hole Position/RPM Chart Choke Linkage Control Bracket Governor...
  • Page 119 Governor Lever Hole Position (8 mm) Governor Lever Hole 1 Hole 2 Hole 3 Hole 4 8 mm Governor Lever and Hole Position/RPM Chart for CH18 Engines Non-Accelerator Pump Intended Maximum RPM Accelerator Pump Carburetor Governor Shaft Carburetor Confi guration...
  • Page 120 Reassembly 8 mm Governor Lever and Hole Position/RPM Chart for CH750 Engines Governor Shaft Intended Maximum RPM With Governed Idle System Confi guration High Idle Spring Color Hole No. 3888 3600 Blue 3780 3500 Purple Standard 3672 3400 Orange 3564 3300 Green (Parent Material)
  • Page 121 Reassembly Governor Lever and Hole Position/RPM Chart for Install Oil Sentry (if equipped) ™ CH680 Engines (No Throttle Stop) 1. Apply pipe sealant with Tefl on (Loctite 592™ ® ® ® Gov. Lever Governor Spring or equivalent) to threads of Oil Sentry switch and High Idle RPM Hole No.
  • Page 122 Reassembly Torque Specifi cations-Covers Install Valve Covers Gasket/RTV 3.4 N·m (30 in. lb.) Torque Sequence Black O-ring w/shoulder screws 5.6 N·m (50 in. lb.) w/screws and spacers 9.9 N·m (88 in. lb.) Yellow or Brown O-ring w/integral spacers 9.0 N·m (80 in. lb.) Install Air Cleaner Assembly Low-Profi...
  • Page 123 Reassembly Install Muffl er Connect Spark Plug Leads 1. Install port liners (if equipped), slotted end fi rst, into Connect leads to spark plugs. exhaust ports until fi nger tight. (Exhaust components will press them to fi nal depth.) Install exhaust Prepare Engine for Operation gaskets and muffl...
  • Page 124 © 2022 by Kohler Co. All rights reserved. KohlerEngines.com 24 690 06 Rev. P...

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