1988 Honda CR125 Service Manual

The 1988 Honda CR125 is a high-performance 125cc two-stroke motocross motorcycle featuring liquid cooling, a 6-speed transmission, and advanced suspension components. This service manual covers maintenance procedures, specifications, troubleshooting, and repair instructions for engine, chassis, electrical systems, and routine service intervals. Below are key sections for safety, specifications, maintenance procedures, troubleshooting, and technical data.

1. Specifications 2. Maintenance Schedule 3. Engine Service 4. Chassis & Suspension 5. Electrical System 6. Fuel System 7. Transmission 8. Brake System 9. Troubleshooting 10. Technical Data 11. Safety Information

Specifications

Key technical specifications for the 1988 Honda CR125 motocross motorcycle.

Component	Specification
Engine Type	124.8cc liquid-cooled single-cylinder two-stroke
Bore x Stroke	54.0mm x 54.5mm
Compression Ratio	8.2:1
Carburetor	Keihin PE28
Transmission	6-speed constant mesh
Final Drive	520 chain
Suspension Front	43mm Showa conventional fork
Suspension Rear	Pro-Link single shock
Brakes Front	Single disc
Brakes Rear	Single disc
Dry Weight	91 kg (201 lbs)
Fuel Capacity	8.5 liters (2.2 gallons)

Maintenance Schedule

Recommended service intervals for optimal performance and longevity.

After break-in (3 hours): Change engine oil, check/adjust chain tension, inspect brakes
Every 10 hours: Clean air filter, check spark plug, inspect wheel bearings
Every 20 hours: Change transmission oil, inspect suspension linkage, check spoke tension
Every 40 hours: Replace piston and rings, inspect reed valve, clean power valve
Every 60 hours: Replace wheel bearings, inspect swingarm bearings, check steering head bearings

WARNING! Always use genuine Honda parts and recommended lubricants. Wear appropriate safety gear during maintenance.

Engine Service

Procedures for engine maintenance, repair, and performance optimization.

Top end rebuild: Remove cylinder head, replace piston and rings, inspect cylinder
Power valve service: Clean and lubricate HPP system components
Reed valve inspection: Check for cracks or warping, replace if necessary
Crankcase seals: Replace if engine shows air leak symptoms
Cooling system: Check radiator, hoses, and water pump for leaks

CAUTION! Engine components operate at high temperatures; allow proper cooling before service.

Chassis & Suspension

Front Fork: 43mm Showa, oil capacity 435ml per leg
Rear Shock: Pro-Link system, nitrogen pressure 142 psi
Frame: Aluminum perimeter design
Swingarm: Aluminum construction with needle bearings
Wheel Alignment: Check and adjust chain adjusters for proper alignment
Steering Head: Tapered roller bearings, torque to 35 Nm

Electrical System

Complete electrical system specifications and troubleshooting procedures.

Ignition: CDI electronic ignition, spark plug NGK BR9ES. Lighting: Competition-only lighting coil (optional). Battery: Not applicable - magneto powered.

Testing procedures: Check stator resistance (20-30 ohms), ignition coil primary (0.1-0.3 ohms), spark plug gap (0.6-0.7mm).

Fuel System

Carburetor settings and fuel mixture specifications.

Main jet: #180 (standard elevation)
Pilot jet: #55
Needle: 6BHY38-3, clip position 2nd from top
Float height: 18.5mm
Air screw: 1.5 turns out

Tip: Use 32:1 fuel/oil mixture with high-quality 2-stroke oil. Clean fuel filter regularly.

Transmission

6-speed transmission service and gear ratios.

Gear ratios: 1st 2.083, 2nd 1.722, 3rd 1.444, 4th 1.227, 5th 1.083, 6th 0.963
Oil capacity: 750ml Honda HP Transmission Oil or equivalent
Shift mechanism: Inspect shift drum and forks for wear
Clutch: Fiber plates (7), metal plates (6), spring free length 41.5mm
Primary reduction: 3.166

WARNING! Always drain transmission when warm for complete oil removal.

Brake System

Front and rear disc brake maintenance and specifications.

Component	Specification
Front Disc	240mm diameter
Rear Disc	220mm diameter
Brake Pads	Replace when worn to 1.0mm thickness
Brake Fluid	DOT 4
Master Cylinder	Front 11mm, Rear 12.7mm

Troubleshooting

Common issues and diagnostic procedures.

Symptom	Possible Cause	Corrective Action
Hard starting	Fouled plug, compression loss	Replace spark plug, check compression (120+ psi)
Poor top end power	Clogged exhaust, worn piston	Clean expansion chamber, inspect piston/cylinder
Transmission noise	Worn bearings, low oil	Check oil level, inspect transmission bearings
Overheating	Lean jetting, coolant leak	Check jetting, inspect cooling system
Clutch slippage	Worn plates, weak springs	Measure clutch components, replace as needed

Technical Data

Torque specifications and critical measurements.

Cylinder Head: 20 Nm
Spark Plug: 12 Nm
Front Axle: 65 Nm
Rear Axle: 110 Nm
Sprocket Nuts: 55 Nm
Oil Drain Plug: 25 Nm
Fork Cap: 25 Nm
Shock Mounts: 40 Nm

Safety Information

Important safety precautions for service and operation.

Always wear eye protection when working on motorcycle. Use proper jack stands when lifting. Keep work area clean and organized. Never operate engine in enclosed space. Follow all torque specifications precisely. Dispose of fluids according to local regulations.

Service Support: Contact authorized Honda dealer for technical assistance. Genuine parts available through Honda dealership network.