1986 Suzuki RM125 Service Manual

The 1986 Suzuki RM125 is a high-performance motocross motorcycle featuring a liquid-cooled 124cc two-stroke engine, 6-speed transmission, front and rear disc brakes, and advanced suspension system for competitive racing. This service manual provides comprehensive technical information for maintenance, repair, and troubleshooting procedures. Below are key sections covering specifications, maintenance schedules, engine service, chassis repair, and troubleshooting.

1. General Information 2. Specifications 3. Maintenance Schedule 4. Engine Service 5. Fuel System 6. Electrical System 7. Chassis and Suspension 8. Brake System 9. Troubleshooting 10. Wiring Diagrams

General Information

This manual covers the 1986 Suzuki RM125 motocross model. Includes safety precautions, tool requirements, and general service procedures.

Section	Description
Identification	Frame and engine serial number locations
Safety First	Important safety precautions for service work
Special Tools	Required tools for proper maintenance
Torque Specifications	Critical fastener torque values
Lubrication Points	Grease and oil application locations

Specifications

Engine Type: 124cc, liquid-cooled, two-stroke single
Bore x Stroke: 56.0 x 50.0 mm
Compression Ratio: 8.5:1
Carburetor: Mikuni VM32SS
Transmission: 6-speed constant mesh
Final Drive: DID 520 chain
Suspension Front: Telescopic fork, 10.6 in travel
Suspension Rear: Swingarm with shock, 11.8 in travel
Brakes Front/Rear: Hydraulic disc
Fuel Capacity: 2.1 gallons
Dry Weight: 194 lbs

Maintenance Schedule

Regular maintenance intervals for optimal performance and longevity.

Before Each Ride: Check fuel, oil, tires, controls, chain tension
Every 15 Hours: Clean air filter, check spark plug
Every 30 Hours: Change transmission oil, check brake pads
Every 60 Hours: Replace spark plug, check wheel bearings
Every 120 Hours: Top end rebuild, suspension service

WARNING! Failure to follow maintenance schedule may result in component failure and safety hazards.

Engine Service

Complete engine disassembly, inspection, and reassembly procedures.

Cylinder Head: Removal, decarbonizing, installation
Cylinder and Piston: Inspection, measurement, ring replacement
Crankcase: Splitting cases, crankshaft service
Transmission: Gear inspection, shift mechanism service
Clutch: Plate replacement, basket inspection
Water Pump: Impeller and seal replacement

CAUTION! Use proper sealing compounds and torque specifications during reassembly.

Fuel System

Carburetor service and fuel delivery system maintenance.

Component	Service Procedure
Carburetor	Cleaning, jetting, float level adjustment
Fuel Tank	Removal, cleaning, petcock service
Air Filter	Cleaning, oiling, proper installation
Reed Valve	Inspection, replacement criteria

Tip: Always use fresh fuel mixture and clean air filter for optimal performance.

Electrical System

Complete electrical system testing and component service.

Ignition System: CDI unit testing, coil service
Charging System: Stator testing, regulator check
Lighting System: Bulb replacement, wiring repair
Kill Switch: Testing and replacement procedure
Spark Plug: Proper gap and heat range selection

Chassis and Suspension

Frame, suspension, and steering component service.

Front Fork: Oil change, seal replacement, spring service
Rear Shock: Nitrogen charge, seal head service
Steering Head: Bearing adjustment and replacement
Swingarm: Bearing service and pivot maintenance
Wheels and Hubs: Bearing replacement, spoke tensioning

WARNING! Always check suspension components for cracks or damage before riding.

Brake System

Hydraulic disc brake service and maintenance procedures.

Component	Service Procedure
Brake Pads	Inspection and replacement criteria
Brake Discs	Measurement and runout check
Brake Calipers	Piston service, seal replacement
Master Cylinders	Rebuild procedures, lever adjustment
Brake Lines	Inspection and replacement intervals

Troubleshooting

Common problems and their solutions for the 1986 RM125.

Symptom	Possible Cause	Corrective Action
Hard starting	Fouled plug, compression loss	Replace spark plug, check compression, clean carburetor
Poor performance	Clogged jets, air leak	Clean carburetor, check reed valve, inspect crank seals
Transmission noise	Worn gears, low oil	Inspect transmission, change oil, check bearing play
Overheating	Low coolant, water pump failure	Check coolant level, inspect water pump, clean radiator
Brake fade	Contaminated pads, air in system	Replace pads, bleed brakes, clean discs

Wiring Diagrams

Complete electrical schematics and connector locations.

Main Harness: Color-coded wiring diagram
CDI System: Ignition circuit testing points
Lighting Circuit: Headlight and taillight wiring
Connector Locations: Main plug and component locations
Ground Points: Critical grounding locations

Service Information: For technical support, contact authorized Suzuki dealer or visit Suzuki technical publications.