Category:
Motocross / Off-road Competition
Target Audience:
Motocross racers, mechanics, and enthusiasts
Competitors:
KTM 85 SX, Honda CR85R, Suzuki RM85, Kawasaki KX85
Vehicle Focus:
High-performance two-stroke engine, competitive chassis, track-focused design.
Manual Value:
Essential for maintaining peak performance and longevity of a competition machine.
Engine:
Complete engine tear-down, rebuild, component inspection, lubrication, cooling, exhaust.
Transmission:
Gearbox, clutch, shifting mechanism, lubrication, disassembly, assembly.
Fuel System:
Carburetor (Mikuni VM28SS), fuel lines, fuel tank, troubleshooting.
Electrical System:
Ignition system, lighting, wiring diagrams, troubleshooting, CDI unit.
Suspension:
Front forks (Kayaba USD), rear shock absorber (Monoshock), linkage, adjustments, service.
Brakes:
Front disc brake, rear disc brake, hydraulic system, pads, fluid replacement, bleeding.
Chassis And Frame:
Frame, subframe, bodywork, seating, controls, steering.
Cooling System:
Liquid cooling system, radiator, hoses, coolant specifications.
Wheels And Tires:
Wheel types, spoke tension, tire pressure, rim specifications.
Maintenance:
Routine maintenance checks, lubrication points, cleaning, adjustments.
Troubleshooting:
Diagnostic flowcharts for common issues, symptom-based troubleshooting.
Repair:
Step-by-step instructions for component removal, repair, and reinstallation.
Rebuild:
Complete engine and transmission rebuild procedures.
Diagnostics:
Fault finding for ignition, fueling, and mechanical issues.
Depth:
Comprehensive from basic maintenance to complete engine and suspension overhaul.
Detail Level:
Factory-level detail with clear instructions and visuals.
Illustrations:
Includes numerous diagrams, exploded views, and photographs.
Special Tools:
Lists and illustrations of required special tools for specific procedures.
Type:
Liquid-cooled, 2-stroke, reed valve, single-cylinder
Bore X Stroke:
47.5 mm x 47.2 mm
Compression Ratio:
9.6:1 (at TDC)
Carburetor:
Mikuni VM28SS
Ignition:
CDI (Capacitor Discharge Ignition)
Horsepower:
Approximately 22-24 HP (Estimated, factory data may vary)
Torque:
Not officially published by Yamaha for this model, but indicative of strong mid-range power.
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Fuel Oil Mixture:
50:1 ratio (Yamalube 2-stroke oil or equivalent)
Oil Change:
Every 10-15 hours of riding or annually. Specific interval in manual.
Air Filter:
Clean/replace every 5-10 hours or as needed based on conditions.
Spark Plug:
Inspect/replace every 10-20 hours of riding.
Top End Rebuild:
Recommended every 40-60 hours of hard racing, depending on usage and maintenance.
Engine Oil:
Yamalube 2-stroke oil (50:1 mix) or equivalent high-quality JASO FD certified oil.
Transmission Oil:
Yamalube Gear Oil SAE 80 API GL-4 or equivalent.
Coolant:
Yamaha's recommended premixed coolant or a 50/50 mix of ethylene glycol-based coolant and distilled water.
Brake Fluid:
DOT 3 or DOT 4 brake fluid.
Common Problems:
Can include clutch wear, piston ring wear, carburetor jetting sensitivity, and front fork seal leaks if not properly maintained. These are common to high-performance 2-strokes.
Heritage:
Yamaha has a long and successful history in motocross racing, consistently producing competitive machinery.
Yz Lineage:
The YZ85 is part of Yamaha's highly regarded YZ line, known for performance and innovation in the small-displacement motocross segment.
Production Era:
The YZ85 was introduced in 2002, replacing the YZ80, and has seen continuous updates through various generations.
