1987 YZ80 Manual

The 1987 Yamaha YZ80 is a high-performance 80cc two-stroke motocross bike designed for youth and beginner riders. Featuring a liquid-cooled engine, 6-speed transmission, front and rear suspension systems, and lightweight frame construction. Below are key sections for safety, features, maintenance, operation, specifications, and troubleshooting.

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

Features at a Glance

Key components: Liquid-cooled 80cc two-stroke engine, 6-speed transmission, front telescopic forks, rear monoshock suspension, aluminum swingarm, drum brakes front and rear.

Feature	Description
Engine Type	Liquid-cooled 2-stroke single cylinder
Displacement	79cc
Transmission	6-speed constant mesh
Front Suspension	Telescopic forks
Rear Suspension	Monoshock swingarm
Front Brake	Drum brake
Rear Brake	Drum brake
Fuel Capacity	1.3 gallons
Seat Height	30.3 inches
Dry Weight	134 lbs

Installation & Assembly

Unpack and inspect contents. Assemble on stable surface.

Install handlebars: Position and tighten clamp bolts to specification.
Mount front wheel: Install wheel between forks, secure axle nuts.
Install controls: Attach throttle, clutch, and brake levers.
Add fluids: Fill with recommended 2-stroke oil and fuel mixture.

WARNING! Motorcycle is heavy; lift with care to avoid injury. Ensure all fasteners are properly torqued.

First-Time Setup

Complete pre-ride inspection before starting engine.

Check tire pressure: Front 12 psi, Rear 12 psi.
Adjust controls: Position levers for comfortable reach.
Set suspension: Adjust preload for rider weight.
Fuel mixture: Prepare 32:1 gas/oil ratio.

CAUTION! Always wear proper safety gear including helmet, gloves, and boots.

Specifications

Engine: 79cc liquid-cooled 2-stroke
Bore x Stroke: 47.0 x 45.6mm
Compression Ratio: 8.3:1
Carburetor: Mikuni VM24SS
Ignition: CDI
Transmission: 6-speed wet clutch
Final Drive: Chain
Frame: Steel backbone
Wheelbase: 49.0 inches
Ground Clearance: 11.8 inches

Controls and Operation

Familiarize yourself with all controls before riding.

Left Handlebar: Clutch lever, horn button, turn signal switch (if equipped), high/low beam switch.

Right Handlebar: Throttle, front brake lever, engine stop switch, start button.

Foot Controls: Gear shift lever (left), rear brake pedal (right).

Starting Procedure: Turn fuel on, choke if cold, kick start firmly. Allow proper warm-up before riding.

Maintenance Procedures

Regular maintenance ensures optimal performance and longevity.

Air filter: Clean every 10 hours of operation
Spark plug: Check/replace every 20 hours
Chain adjustment: Maintain 1-1.5 inches of free play
Brake adjustment: Check lever/pedal free play
Suspension: Check for leaks and proper operation

Tip: Keep maintenance log to track service intervals.

Engine Break-in

Proper break-in is critical for engine longevity.

First hour: Vary throttle position, avoid sustained high RPM
Second hour: Gradually increase load and RPM
Third hour: Normal riding with occasional full throttle
After break-in: Change transmission oil, check all fasteners

WARNING! Do not exceed 3/4 throttle during first hour of operation.

Safety Features

Engine stop switch: Immediate engine shutdown. Kickstand safety switch: Prevents starting in gear. Proper lighting: Headlight, taillight for visibility.

Care & Cleaning

Clean after each ride. Use mild soap and water; avoid high-pressure spray near seals and bearings.

CAUTION! Do not spray water directly at air filter, chain, or electrical components.

Regulatory Information

Designed for closed-course competition use only. Not legal for street use in most jurisdictions. Yamaha Motor Corporation. For support, contact authorized Yamaha dealer or visit Yamaha-motor.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel, spark, compression	Check fuel flow, spark plug, compression; clean carburetor.
Poor performance	Clogged air filter, jetting	Clean air filter; check carburetor jetting; inspect exhaust.
Hard shifting	Clutch adjustment, oil	Adjust clutch cable; change transmission oil.
Brakes weak	Worn pads, adjustment	Inspect brake pads; adjust cable tension.
Overheating	Coolant, jetting	Check coolant level; verify proper carburetor jetting.

Reset: None required - mechanical systems only.

Service: Contact authorized Yamaha dealer for technical support.