1987 Honda TRX 125 Service Manual PDF

The 1987 Honda TRX 125 is a reliable all-terrain vehicle featuring a 124cc four-stroke engine, automatic clutch, shaft drive, and electric start. This comprehensive service manual covers maintenance procedures, troubleshooting, specifications, and repair instructions for the complete ATV system including engine, transmission, suspension, brakes, and electrical components.

1. General Information 2. Specifications 3. Periodic Maintenance 4. Engine Service 5. Fuel System 6. Electrical System 7. Transmission & Drive 8. Suspension & Steering 9. Brake System 10. Troubleshooting

General Information

This manual provides detailed service information for the 1987 Honda TRX 125 ATV. Includes safety precautions, tool requirements, and general maintenance procedures.

Component	Description
Model	TRX125
Year	1987
Type	All-Terrain Vehicle
Engine Type	4-stroke, air-cooled, single cylinder
Displacement	124cc
Starting System	Electric & Kick Start
Drive System	Shaft Drive
Transmission	Automatic clutch, 5-speed

Specifications

Engine: 124cc 4-stroke OHC, air-cooled
Bore x Stroke: 56.5mm x 49.5mm
Compression Ratio: 9.3:1
Carburetor: 22mm piston valve
Ignition System: CDI
Transmission: 5-speed with automatic clutch
Final Drive: Shaft
Suspension Front: Independent double wishbone
Suspension Rear: Swingarm
Brakes Front/Rear: Drum
Tires Front/Rear: 21x7-10 / 22x11-8
Fuel Capacity: 2.4 gallons
Dry Weight: 297 lbs

Periodic Maintenance

Regular maintenance schedule to ensure optimal performance and longevity.

Engine Oil: Change every 6 months or 600 miles
Oil Filter: Replace every other oil change
Air Filter: Clean every 300 miles, replace as needed
Spark Plug: Clean and gap every 600 miles, replace annually
Valve Clearance: Check every 1200 miles
Drive Shaft: Lubricate every 1200 miles
Brake Fluid: Check monthly, replace annually
Tire Pressure: Check before each ride

WARNING! Always perform maintenance in well-ventilated area. Use proper safety equipment.

Engine Service

Complete engine disassembly, inspection, and reassembly procedures.

Cylinder Head Removal: Remove camshaft, valves, inspect for wear
Cylinder & Piston: Measure cylinder bore, inspect piston rings
Crankshaft & Connecting Rod: Check bearing clearance, end play
Camshaft & Timing: Set valve timing, check chain tension
Oil Pump: Inspect for proper operation and pressure
Cooling System: Clean cooling fins, check for obstructions

CAUTION! Torque all fasteners to specified values. Use new gaskets during reassembly.

Fuel System

Carburetor service and fuel delivery system maintenance.

Carburetor Removal: Drain fuel, disconnect linkages
Carburetor Disassembly: Clean all jets, passages, and float bowl
Float Level Adjustment: Set to 18.5mm
Pilot Screw Setting: Initial setting 2-1/8 turns out
Fuel Tank: Inspect for rust, clean as needed
Fuel Filter: Replace annually or when clogged

WARNING! Work in well-ventilated area away from ignition sources.

Electrical System

Complete electrical system testing and repair procedures.

Component	Specification
Battery	12V 5Ah
Charging System	AC generator
Ignition Timing	15° BTDC at 1700 RPM
Spark Plug	NGK DR8ES-L
Spark Plug Gap	0.6-0.7mm (0.024-0.028 in)
Fuse	10A

Testing Procedures: Continuity tests, voltage measurements, component replacement.

Transmission & Drive

Transmission service and final drive maintenance.

Transmission Oil: Change every 12 months or 1200 miles
Clutch Adjustment: Check free play, adjust cable
Shift Mechanism: Inspect shift drum, forks, and gears
Drive Shaft: Lubricate universal joints and splines
Final Gear Oil: Change annually
Wheel Bearings: Inspect for wear, replace as needed

NOTE: Use Honda GN4 10W-40 oil or equivalent for transmission.

Suspension & Steering

Front and rear suspension service and steering system maintenance.

Front Suspension: Double wishbone with shock absorbers
Rear Suspension: Swingarm with single shock
Steering Stem: Adjust bearing preload
Wheel Alignment: Check toe-in, adjust as needed
Shock Absorbers: Inspect for leaks, check damping
A-arms & Bushings: Inspect for wear and damage

CAUTION! Always support ATV securely when working on suspension.

Brake System

Front and rear brake service and adjustment procedures.

Brake Adjustment: Adjust lever free play
Brake Shoes: Inspect for wear, replace if worn
Brake Drums: Measure diameter, check for scoring
Brake Cables: Lubricate regularly, check for fraying
Parking Brake: Adjust for proper operation
Brake Fluid: DOT 3 or DOT 4

WARNING! Test brakes thoroughly before riding. Replace worn components immediately.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel, spark, or compression issue	Check fuel flow, spark plug, compression
Poor performance	Clogged air filter, carburetor issues	Clean air filter, service carburetor
Electrical failure	Battery, fuse, or wiring problem	Test battery, check fuses, inspect wiring
Transmission slipping	Worn clutch, low oil level	Adjust clutch, check oil level
Brakes not working	Worn shoes, adjustment needed	Inspect shoes, adjust brakes
Overheating	Low oil, clogged fins, lean mixture	Check oil level, clean fins, adjust carburetor

Technical Support: Contact Honda dealer for complex issues or genuine parts.