Category:
Motocross Youth/Junior Performance Motorcycle
Target Demographic:
Young riders, aspiring motocross competitors, and recreational off-road enthusiasts.
Competitors:
Honda CR80R, Kawasaki KX80, Suzuki RM80.
Performance Focus:
Lightweight chassis, potent 80cc 2-stroke engine, advanced suspension for its class.
Durability:
Yamaha's reputation for building robust and reliable competition machines.
Primary Coverage:
Comprehensive service, repair, and maintenance for the 1999 Yamaha YZ80.
Secondary Coverage Note:
Applicable to similar model years and variations of the YZ80, though specific details may differ.
Estimated Page Count:
Approximately 300-400 pages (typical for a full service manual of this era and type).
Type:
Service Repair Workshop Manual
Format:
Digital (likely PDF, searchable text recommended).
Engine:
Detailed breakdown of the 80cc 2-stroke engine, including top-end (cylinder, piston, rings, head), bottom-end (crankshaft, connecting rod, bearings), cooling system (air-cooled), lubrication (premix ratio), and ignition system (CDI).
Fuel System:
Carburetor (Mikuni VM series typically), fuel tank, fuel lines, fuel filter, and fuel pump (if applicable).
Transmission:
6-speed sequential gearbox, clutch system (wet multi-plate), gear shift linkage, and internal transmission components.
Suspension:
Front telescopic forks (Kayaba or similar), rear Monocross suspension system with adjustable shock absorber, fork seals, oil specifications, and linkage maintenance.
Brakes:
Front and rear hydraulic disc brake systems, brake caliper service, master cylinder overhaul, brake fluid type and bleeding procedures.
Electrical System:
Ignition system (CDI), lighting (if equipped), wiring diagrams, battery specifications (if applicable), fuses, and component testing.
Chassis And Bodywork:
Frame inspection and repair, body panels (fenders, tank shrouds, seat), footpegs, handlebars, and controls.
Wheels And Tires:
Spoke wheel maintenance, tire sizes, inflation pressures, and rim specifications.
Routine Maintenance:
Oil changes (premix ratio), air filter cleaning/replacement, spark plug inspection/replacement, chain adjustment and lubrication, brake system checks.
Engine Overhaul:
Top-end rebuild (piston, rings, cylinder hone), bottom-end inspection and bearing replacement, crankshaft runout checks.
Transmission Service:
Clutch adjustment and replacement, gearbox disassembly and reassembly, gear inspection.
Suspension Rebuild:
Front fork seal replacement, fork oil change, rear shock absorber service and adjustments.
Brake System Overhaul:
Caliper seal replacement, master cylinder rebuild, brake line bleeding, rotor inspection.
Troubleshooting:
Diagnostic procedures for common issues related to starting, running, performance, and electrical systems.
Carburetor Tuning:
Cleaning, adjustment, and jetting procedures for the Mikuni carburetor.
Depth:
Comprehensive, covering everything from basic rider maintenance to complete engine and chassis rebuilds.
Detail Level:
Detailed exploded views, torque specifications, measurement tolerances, and step-by-step instructions with accompanying diagrams.
Type:
Liquid-cooled (Note: YZ80 is typically air-cooled, manual likely reflects this. Manual should clarify cooling system.)
Configuration:
Single-cylinder, 2-stroke
Bore X Stroke:
47.5 mm x 44.4 mm
Compression Ratio:
8.4:1 (typical, manual will confirm exact spec)
Reed Valve System:
Yes (typical for performance 2-strokes)
Horsepower:
Approximately 15-18 HP (estimated, actual figures vary by specific tuning and model year)
Torque:
Not typically advertised for this class, but the manual will detail torque curves.
Carburetor Model:
Mikuni VM24SS (common for this model)
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Premix Ratio:
50:1 (Yamalube 2R or equivalent high-quality 2-stroke oil recommended)
Length:
Approximately 1845 mm (manual will provide exact figure)
Width:
Approximately 790 mm (manual will provide exact figure)
Height:
Approximately 1140 mm (manual will provide exact figure)
Wheelbase:
Approximately 1250 mm (manual will provide exact figure)
Dry Weight:
Approximately 71 kg (manual will provide exact figure)
Fuel Capacity:
Approximately 5.5 Liters (manual will confirm)
Oil Capacity Transmission:
Approximately 0.8 Liters (manual will confirm)
Spark Plug Inspection:
Every 10-15 hours of use or as needed. Manual will provide specific gap and condition checks.
Air Filter Cleaning:
After every ride or as needed, depending on riding conditions. Manual will detail cleaning and oiling procedure.
Chain Lubrication Adjustment:
After every ride or as needed. Manual will specify proper slack.
Transmission Oil Change:
Every 20-30 hours of use or annually. Manual will specify exact interval.
Fork Oil Change:
Recommended every 50-100 hours of use, or if performance degrades. Manual will specify oil type and level.
Engine Oil Premix:
Yamalube 2R or equivalent high-performance 2-stroke racing oil at 50:1 ratio.
Transmission Oil:
Yamalube Gear Oil SAE 80W or equivalent.
Brake Fluid:
DOT 4 hydraulic brake fluid.
Fork Oil:
Manual will specify viscosity grade (e.g., SAE 0W-20, SAE 5W) and level.
Common Wear Items:
Piston rings, clutch plates, swingarm bushings, wheel bearings, and fork seals are common wear items on this type of performance 2-stroke.
Carburetor Maintenance:
Carburetor jets can become clogged with time and improper fuel storage. Regular cleaning is essential.
2 Stroke Specific:
Proper premix ratio and quality oil are critical to prevent premature engine wear and seizing.
Yamaha Motorsports Legacy:
Yamaha has a long and storied history in professional motocross and off-road racing, building championship-winning machines across various displacement classes.
Yz80 Lineage:
The YZ80 has been a staple in Yamaha's junior motocross lineup for decades, consistently evolving with updated suspension, chassis, and engine technology to remain competitive.
Production Period:
The YZ80 model was in continuous production for many years, with the 1999 model representing a significant iteration within its lifecycle.
