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Discusses safety information and precautions for service and repair.
General safety practices for service tasks, including protective wear and equipment.
Covers service and repair procedures for Honda GX270H/390H1 engines.
Highlights the importance of safety messages and symbols (DANGER, WARNING, CAUTION).
Guidelines for using Honda Genuine parts, tools, and lubricants.
Explains symbols used in the manual for specific service procedures.
Lists key engine specifications like displacement, bore, stroke, and power.
Graphical representation of engine performance data (torque and power).
Technical drawings showing engine dimensions and component layouts.
Specifies standard and service limit values for engine parts and their measurements.
Lists recommended torque values for various engine bolts and nuts.
Details lubrication points and recommended sealants or oils for engine assembly.
Lists specialized tools required for servicing the engine and its components.
Illustrates the correct routing of electrical harnesses and fuel/breather tubes.
Outlines the recommended service intervals for regular maintenance items.
Procedure for checking and changing the engine oil level.
Procedure for checking and changing the reduction case oil level.
Steps for inspecting, cleaning, or replacing the air cleaner element.
Guide for inspecting and adjusting the spark plug gap.
Procedure for removing and installing a new spark plug.
Procedure for checking and adjusting valve clearances.
Preliminary checks and advice before starting troubleshooting.
Diagnostic flow chart for hard starting engine problems.
Troubleshooting guide for engine speed problems.
Troubleshooting steps for when the engine fails to stop.
Procedure for removing and installing the engine's fan cover.
Procedure for removing and installing the fuel tank.
Steps for removing and installing the air cleaner assembly.
Procedure for removing and installing the carburetor.
Detailed steps for disassembling and assembling the carburetor.
Instructions for cleaning the carburetor body and its passages.
Steps for inspecting the carburetor, including float level.
Procedure for removing and installing the governor arm and control base assembly.
Guide for adjusting the engine's maximum speed setting.
Steps for removing/installing governor parts for manual operation.
Governor system service for types other than manual operation.
Procedure for adjusting maximum speed on manual control type engines.
Electrical diagram of the charging system components.
Diagnostic flow chart for charging system problems.
Procedure for removing and installing the cooling fan and flywheel.
Steps for removing and installing the charge/lamp coil.
Procedure for inspecting the charge/lamp coil's electrical properties.
Electrical diagram of the ignition system.
Diagnostic guide for ignition system problems.
Procedure for removing and installing the ignition coil.
Steps for checking and adjusting the ignition coil air gap.
Procedure for testing for spark at the spark plug.
Procedure for inspecting the ignition coil's primary and secondary resistance.
Electrical diagram of the starting system.
Diagnostic guide for starting system problems.
Procedure for removing and installing the recoil starter.
Detailed steps for disassembling and assembling the recoil starter.
Procedures for inspecting recoil starter operation and pulley.
Steps for removing and installing the starter motor.
Detailed procedure for disassembling and assembling the starter motor.
Procedures for inspecting starter motor performance and brush length.
Identifies the location of electrical components on the engine.
Procedure for removing and installing the control box.
Detailed steps for disassembling and assembling the control box.
Procedure for inspecting the oil level switch for continuity.
Procedure for inspecting the engine stop switch's continuity.
Procedure for inspecting the combination switch's continuity.
Procedure for inspecting the silicon rectifier's continuity.
Procedure for inspecting the circuit protector's continuity.
Procedure for removing and installing the muffler assembly.
Steps for removing and installing the muffler with solid protector.
Procedure for removing and installing the muffler with inner/outer protectors.
Procedure for removing and installing the cylinder head assembly.
Detailed steps for disassembling and assembling the cylinder head.
Procedures for inspecting cylinder head and valve components.
Steps for reconditioning valve seats.
Detailed procedure for removing and installing the cylinder head, including torque specs.
Procedure for measuring cylinder compression using a gauge.
How to check for cylinder head warpage using measurement tools.
Procedure for measuring and reconditioning valve seat width.
Procedure for measuring valve stem outer diameter and checking for wear.
How to calculate and check valve guide-to-stem clearance.
Procedure for measuring valve spring free length and checking against limits.
Procedure for cleaning, marking, and reconditioning valve seats.
Procedure for removing and installing the crankcase cover.
Steps for removing and installing crankshaft, balancer, and piston assemblies.
Steps for disassembling and assembling the reduction unit.
Steps for disassembling and assembling the governor mechanism.
Detailed procedure for disassembling and assembling the piston.
Inspection procedures for various engine internal components.
Inspection procedures for reduction unit components.
Procedure for replacing bearings and oil seals on the crankcase cover side.
Steps for replacing crankshaft bearings on the flywheel side.
Procedure for replacing GX270H crankshaft oil seal on the cylinder barrel side.
Procedure for replacing bearings and oil seals on GX390H1 cylinder barrel side.
Procedure for replacing GX270H PTO shaft oil seals on 1/2 reduction clutch type.
Procedure for replacing GX390H1 shaft bearings/oil seals on 1/6 reduction gear type.
Procedure for replacing GX270H shaft bearings on crankcase cover side.
Procedure for replacing GX390H1 shaft bearings on crankcase cover side.
Detailed steps for removing and installing crankshaft, balancer, and piston.
Detailed procedure for disassembling and assembling the piston, rings, and pin.
Inspection procedures for various engine internal components.
Inspection procedures for reduction unit components.
Procedure for measuring piston skirt outside diameter.
How to calculate and check piston-to-cylinder clearance.
Procedure for measuring piston ring side clearance.
How to measure connecting rod big end clearance.
Procedure for measuring connecting rod small end inside diameter.
Procedure for measuring connecting rod big end inside diameter.
Procedure for measuring crankpin outside diameter.
Procedure for measuring connecting rod big end oil clearance using plastigauge.
How to measure crankshaft runout using a dial indicator.
Procedure for measuring camshaft cam height.
Procedure for measuring camshaft outside diameter.
Guide on understanding wiring diagrams, connectors, and symbols.
Contains actual wiring diagrams for the system.
Detailed guide on reading wiring diagrams, including symbol meanings and terminal identification.
Wiring diagram for models without a charge coil.
Wiring diagram for models with 1 A/3 A charge coils.
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