1986 Kawasaki KX 125 Manual

The 1986 Kawasaki KX 125 is a high-performance motocross bike featuring a liquid-cooled 2-stroke 125cc engine, 6-speed transmission, Uni-Trak rear suspension system, front disc brake, and aluminum swingarm. This manual covers essential information for maintenance, operation, specifications, and troubleshooting of this classic motocross machine.

1. Features at a Glance 2. Installation & Assembly 3. First-Time Setup 4. Specifications 5. Controls and Operation 6. Maintenance Procedures 7. Engine Service 8. Suspension & Chassis 9. Care & Cleaning 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Liquid-cooled 2-stroke engine, Uni-Trak rear suspension, front disc brake, aluminum swingarm, 6-speed transmission.

Feature	Description
Engine Type	Liquid-cooled 2-stroke single cylinder
Displacement	124cc
Transmission	6-speed constant mesh
Front Suspension	Telescopic fork
Rear Suspension	Uni-Trak system
Front Brake	Hydraulic disc
Rear Brake	Drum brake
Fuel Capacity	2.1 gallons (8 liters)
Dry Weight	198 lbs (90 kg)
Frame Type	Steel semi-double cradle

Installation & Assembly

Unpack and inspect all components. Ensure proper assembly before operation.

Handlebar installation: Mount handlebars to triple clamp, tighten bolts to specified torque.
Front wheel installation: Install wheel between fork legs, align axle, tighten to specification.
Controls setup: Install throttle, clutch, and brake levers with proper free play.
Fuel system: Add proper 2-stroke oil mixture to fuel tank.

WARNING! Motorcycle is heavy; use proper lifting techniques. Ensure all fasteners are properly torqued.

First-Time Setup

Complete initial setup before first ride.

Fuel mixture: Prepare 32:1 fuel/oil ratio for break-in period.
Suspension adjustment: Set sag and clickers for rider weight and conditions.
Control adjustments: Set lever positions and free play to rider preference.
Pre-ride inspection: Check tire pressure, chain tension, fluid levels.

CAUTION! Always wear proper safety gear. Break in engine properly before hard riding.

Specifications

Engine: 124cc liquid-cooled 2-stroke single
Bore x Stroke: 54.0 x 54.0 mm
Compression Ratio: 8.4:1
Carburetor: Keihin PWK 34mm
Ignition: CDI electronic
Transmission: 6-speed, wet multi-plate clutch
Front Tire: 80/100-21
Rear Tire: 100/90-19
Ground Clearance: 13.0 inches (330mm)
Seat Height: 36.2 inches (920mm)

Controls and Operation

Familiarize yourself with all controls before riding.

Left Side: Clutch lever, choke knob, horn button, turn signal switch, high/low beam switch.

Right Side: Front brake lever, throttle, engine stop switch, start button.

Operation: Start with choke on cold engine. Allow proper warm-up time. Use proper shifting technique - clutch for downshifts, throttle blip for smooth engagement. Always use both brakes for maximum stopping power.

Maintenance Procedures

Regular maintenance ensures optimal performance and longevity.

Air filter service: Clean every 2-3 rides, oil with proper filter oil.
Chain maintenance: Clean and lubricate regularly, adjust tension to 1.2-1.6 inches.
Brake service: Check pad wear, bleed hydraulic system annually.
Suspension service: Change fork oil every 40 hours, shock oil every 80 hours.

Tip: Keep detailed maintenance records for reference.

Engine Service

Proper engine maintenance is critical for 2-stroke performance.

Top end rebuild: Inspect piston and cylinder every 40-60 hours.
Carburetor jetting: Adjust for altitude and temperature changes.
Cooling system: Check coolant level, replace every 2 years.
Power valve: Clean and inspect during top end service.
Ignition timing: Set to factory specification (1.8mm BTDC).
Exhaust system: Regularly clean expansion chamber and silencer.
Crank seals: Replace if evidence of air leaks or transmission oil loss.
Clutch: Adjust free play, replace plates if slipping occurs.

WARNING! Always use proper tools and follow torque specifications. Engine work requires mechanical experience.

Suspension & Chassis

Proper suspension setup enhances handling and comfort.

Front Fork: Adjust compression and rebound damping. Set oil height to 135mm from top. Rear Shock: Set sag to 95-100mm. Adjust high/low speed compression and rebound. Frame: Regularly check for cracks at stress points. Steering Head: Check bearing adjustment annually.

Care & Cleaning

Proper cleaning prevents corrosion and maintains appearance.

Use mild soap and water for routine cleaning. Avoid high-pressure spray near bearings and seals. Lubricate all pivot points after washing. Use aluminum polish on frame and components. Protect plastic with UV-resistant protectant.

CAUTION! Do not spray water directly at electrical components or air filter. Allow engine to cool before washing.

Regulatory Information

This motorcycle is designed for closed-course competition use only. Not legal for street use in most jurisdictions. Always comply with local off-road riding regulations. Wear approved safety equipment including helmet, goggles, boots, gloves, and protective clothing. Kawasaki and KX are registered trademarks of Kawasaki Heavy Industries, Ltd.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Hard starting	Fouled plug, stale fuel	Replace spark plug, drain old fuel, check compression.
Poor performance	Clogged air filter, jetting	Clean air filter, check jetting, inspect power valve.
Transmission issues	Worn gears, shift mechanism	Inspect shift forks, check gear engagement.
Suspension bottoming	Low oil, worn springs	Change fork oil, check spring rate for rider weight.
Brake fade	Contaminated fluid, worn pads	Bleed brakes, replace pads, clean rotors.

Technical Support: Contact authorized Kawasaki dealer for complex issues.

Parts: Genuine Kawasaki parts recommended for optimal performance.