Segment:
Motocross Competition Bike (85cc class)
Target Audience:
Young motocross racers, mechanics, and enthusiasts
Key Competitors:
KTM 85 SX, Honda CR85R, Suzuki RM85, Kawasaki KX85
Vehicle Focus:
High-performance, racing-oriented, lightweight, powerful two-stroke engine
Manual Value Proposition:
Provides essential factory information for maintaining peak performance and reliability of the YZ85
Engine:
Complete engine teardown and rebuild, top-end, bottom-end, carburetor, cooling system
Transmission:
Gearbox inspection, maintenance, and repair, clutch system
Chassis:
Frame, subframe, swingarm, steering system
Suspension:
Front forks (KYB/Speed-Sensitive System), rear shock absorber (Monocross), seals, oil, adjustments
Brakes:
Front and rear hydraulic disc brakes, caliper, master cylinder, lines, bleeding procedures
Electrical:
Ignition system, lighting, CDI unit, wiring diagrams, troubleshooting electrical faults
Fuel System:
Fuel tank, petcock, fuel lines, carburetor (likely Mikuni VM28) specifications and adjustments
Exhaust System:
Expansion chamber, muffler maintenance and inspection
Maintenance:
Routine checks, lubrication, filter cleaning/replacement, chain adjustment, spark plug service
Troubleshooting:
Diagnostic flowcharts for common problems (starting issues, poor performance, etc.)
Repair:
Detailed step-by-step instructions for component removal, disassembly, repair, and reassembly
Torque Specifications:
Crucial torque values for all fasteners and critical components
Special Tools:
Identification and usage of specialized tools required for certain procedures
Rebuilds:
Complete engine teardown and rebuild, gearbox rebuild, suspension rebuild
Depth:
Factory-level detail, suitable for professional technicians and experienced enthusiasts
Diagrams Illustrations:
Abundant with pictures, exploded views, and part diagrams
Diagnostic Information:
Comprehensive troubleshooting guides and diagnostic procedures
Type:
Liquid-cooled, 2-stroke, Reed valve induction
Bore X Stroke:
47.5 mm x 47.8 mm
Compression Ratio:
9.3:1 (typical for this era, check manual for exact)
Horsepower:
Approx. 21.3 HP @ 12,500 rpm (stock, may vary slightly)
Torque:
Approx. 7.8 lb-ft @ 11,500 rpm (stock, may vary slightly)
Carburetor:
Mikuni VM28SS (typical, confirm with manual)
Fuel Type:
Unleaded gasoline, minimum 91 octane (RON + MON)/2 (AKI)
Oil Mixture:
2-stroke pre-mix oil (50:1 or 100:1 depending on oil specification, check manual for Yamaha's recommendation for Yamalube 2)
Type:
CDI (Capacitor Discharge Ignition)
Type:
6-speed, constant mesh
Clutch:
Wet, multiple disc
Gear Ratios:
Detailed in manual, crucial for performance tuning
Transmission Oil:
Yamalube Gear Oil (or equivalent SAE 80 API GL-4, confirm with manual)
Transmission Oil Capacity:
Approx. 0.65 L (confirm with manual)
Wheelbase:
YZ85: 1240 mm (48.8 in), YZ85LW: 1280 mm (50.4 in)
Seat Height:
YZ85: 847 mm (33.3 in), YZ85LW: 884 mm (34.8 in)
Ground Clearance:
YZ85: 330 mm (13.0 in), YZ85LW: 355 mm (14.0 in)
Dry Weight:
YZ85: 73 kg (161 lbs), YZ85LW: 74 kg (163 lbs)
Fuel Tank Capacity:
5.0 L (1.3 US gal)
Oil Change:
As per manual, typically every 5-10 hours of racing or as indicated by service checks
Air Filter Cleaning:
Frequent cleaning recommended, especially in dusty conditions (after every few rides)
Spark Plug Replacement:
As needed, typically every 20-30 hours of riding or based on inspection
Top End Rebuild:
Recommended between 30-50 hours of racing, depending on severity of use and oil quality
Chain And Sprockets:
Regular inspection for wear and adjustment, replacement as needed (typically 15-30 hours)
Coolant:
Ethylene glycol-based antifreeze mixed with distilled water (50:50 ratio), consult manual for specific types and capacities
Brake Fluid:
DOT 3 or DOT 4 hydraulic brake fluid (confirm exact specification and capacity in manual)
Suspension Oil:
Specific fork oil (e.g., KYB 01M) and shock oil, viscosity and quantity detailed in manual.
Common Wear Items:
Piston, piston rings, clutch plates, wheel bearings, chain, sprockets, fork seals, swingarm bushings
Potential Problems:
Carburetor jetting sensitivity to altitude and temperature, potential for overheating if cooling system is not maintained, clutch fade with aggressive use.
Yamaha Legacy:
Yamaha has a long and successful history in off-road and motocross racing, known for innovation and performance.
Yz85 Lineage:
The YZ85 is part of Yamaha's esteemed YZ line, which has consistently evolved to meet the demands of competitive junior motocross.
Manufacturing Origin:
Japan (typical for Yamaha at this time)
Generation:
The 2002 model represents a significant iteration in the YZ85's development.
