Category:
Performance Off-Road Motorcycle
Target User:
Young motocross racers, enthusiasts, mechanics
Competitors:
KTM 85 SX, Suzuki RM85, Kawasaki KX85, Honda CR85
Segment Strength:
Renowned for its powerful two-stroke engine and agile handling, a staple in the junior motocross class.
Vehicle Highlights:
High-performance 85cc liquid-cooled two-stroke engine, YPVS (Yamaha Power Valve System), adjustable suspension, strong braking performance, lightweight chassis.
Manual Benefit:
Empowers owners and technicians with the in-depth knowledge to maintain and repair the YZ85 to factory specifications, ensuring optimal performance and longevity.
Engine Systems:
Top-end rebuild, bottom-end assembly, cooling system, lubrication, ignition, carburetor tuning, exhaust system
Chassis Systems:
Frame, swingarm, rear suspension (Monocross), front suspension (telescopic forks), steering, wheels, tires
Braking Systems:
Front and rear hydraulic disc brakes, caliper servicing, master cylinder overhaul, fluid replacement
Electrical Systems:
Ignition system components, wiring diagrams, lighting (if applicable), basic troubleshooting
Drivetrain Systems:
Clutch operation and service, gearbox inspection and repair, final drive chain and sprockets
Maintenance Procedures:
Scheduled maintenance, oil changes, filter replacement, chain adjustment, spark plug replacement, air filter cleaning
Repair Procedures:
Complete engine teardown and rebuild, suspension fork servicing, shock absorber maintenance, brake pad replacement, clutch service, gearbox disassembly/reassembly
Troubleshooting Guides:
Diagnostic charts for common running issues, starting problems, performance deficiencies, component failure symptoms
Special Tool Requirements:
Identification and usage of specific Yamaha tools for assembly/disassembly
Depth:
Comprehensive, suitable for professional mechanics and experienced DIY enthusiasts
Diagnostic Capabilities:
Detailed diagnostic procedures for identifying root causes of mechanical and electrical faults
Specifications Accuracy:
Includes torque specifications, clearances, fluid capacities, and wear limits
Engine Type:
Liquid-cooled, 2-stroke, reed valve, YPVS
Bore X Stroke:
47.5 mm x 47.8 mm
Compression Ratio:
8.2:1 (at 15.6 MPa or 159 kgf/cm²)
Horsepower:
Approximately 19.5 HP @ 11,000 RPM (estimated, varies by tune)
Torque:
Approximately 9.2 lb-ft @ 10,000 RPM (estimated, varies by tune)
Fuel Type:
Unleaded gasoline (90+ octane recommended)
Fuel Mixture:
Pre-mix (2-stroke oil to gasoline ratio: 50:1 for Yamalube 2A, or manufacturer-specified)
Fuel Tank Capacity:
5.0 Liters (1.3 US gal)
Oil Type:
Yamaha 2M / Yamalube 2A (or equivalent API TC-W3 rated 2-stroke oil)
Transmission Type:
6-speed constant mesh
Clutch Type:
Wet, multiple-disc
Gear Ratios:
Refer to manual for specific ratios (e.g., 1st: 2.467, 2nd: 1.750, 3rd: 1.333, 4th: 1.143, 5th: 1.045, 6th: 0.958)
Transmission Oil Type:
Yamalube Gear Oil 10W-30 (or equivalent API GL-4, SAE 80)
Transmission Oil Capacity:
0.65 Liters (0.69 US qt)
Safety Classification:
Off-road competition vehicle, not designed or equipped for use on public roads.
Braking System:
Hydraulic disc brakes front and rear for strong stopping power and control.
Suspension:
Performance-oriented suspension (front forks and rear Monocross shock) designed for stability and control over rough terrain.
Chassis Design:
Rigid frame designed for agility and rider feedback.
Infotainment System:
N/A (Competition off-road motorcycle)
Assistance Features:
N/A (Competition off-road motorcycle)
Connectivity Options:
N/A (Competition off-road motorcycle)
Ypvs Description:
Yamaha Power Valve System (YPVS) electronically controls exhaust port timing to broaden the powerband and improve low- to mid-range torque.
Oil Change Frequency:
Refer to manual; typically every 10-15 hours of operation or annually.
Air Filter Cleaning:
Regularly, especially after dusty riding conditions; refer to manual for specific intervals.
Spark Plug Replacement:
Refer to manual; typically every 20-30 hours or as needed based on condition.
Chain Adjustment Lubrication:
Check and lubricate chain every 5-10 hours of operation, adjust tension as needed.
Engine Top End Rebuild:
Recommended every 40-60 hours of hard racing use; refer to manual for detailed procedures and piston/ring inspection intervals.
Coolant Type:
High-quality motorcycle antifreeze (50% ethylene glycol and 50% distilled water recommended)
Brake Fluid Type:
DOT 4 hydraulic brake fluid
Common Wear Items:
Clutch plates, piston and rings, chain and sprockets, wheel bearings, brake pads, suspension seals.
Carburetor Tuning:
Sensitivity to altitude and temperature changes requires periodic adjustment.
Ypvs System:
Requires periodic cleaning and proper operation to ensure optimal power delivery.
Manufacturer Heritage:
Yamaha Motor Company, Ltd., a Japanese multinational corporation, is a world leader in motorcycle manufacturing, renowned for its performance, innovation, and racing success.
Yz Series History:
The YZ series has a long and storied history in motocross, with continuous development leading to class-leading performance and multiple championship wins across various classes.
Yz85 Development:
The YZ85 has been a benchmark in the 85cc class, consistently refined for power, handling, and rider ergonomics.
Manufacturing Origin:
Japan
