Target Audience:
Motocross enthusiasts, mechanics, owners of the 1986 Yamaha YZ250
Competitors 1986:
Honda CR250R, Kawasaki KX250, Suzuki RM250
Vehicle Usp 1986:
Powerful two-stroke engine, advanced suspension for its era, competitive pricing
Value Proposition:
Essential resource for maintaining and repairing the iconic 1986 YZ250, ensuring longevity and optimal performance
Engine:
Complete overhaul, troubleshooting, adjustments, performance tuning
Transmission:
Clutch, gearbox, final drive maintenance and repair
Chassis:
Frame, suspension (front and rear), steering, wheels, brakes
Electrical System:
Ignition, lighting, wiring diagrams, troubleshooting
Bodywork:
Fairings, seat, fuel tank, fenders, graphics
Type:
Service Repair Workshop Manual
Engine Mechanical:
Top end (cylinder, piston, rings, head), bottom end (crankshaft, connecting rod, bearings, seals)
Fuel System:
Carburetor (Mikuni VM34SS) overhaul, jetting, adjustments, fuel tank, fuel lines
Cooling System:
Liquid-cooled system, radiator, water pump, coolant specifications
Ignition System:
CDI ignition, spark plug selection, timing adjustments, stator, flywheel
Exhaust System:
Expansion chamber, muffler maintenance and inspection
Clutch System:
Wet multi-plate clutch operation, adjustment, replacement
Transmission Gearbox:
Gear selection, shift drum and forks, gear ratios, oil specifications
Suspension Front:
Telescopic fork (Kayaba), oil levels, seal replacement, damping adjustments
Suspension Rear:
Monocross rear suspension, shock absorber service, linkage maintenance, spring preload
Brakes Front:
Hydraulic disc brake, caliper, master cylinder, brake fluid specifications
Brakes Rear:
Hydraulic disc brake, caliper, master cylinder, brake fluid specifications
Wheels Tires:
Spoke maintenance, bearing service, tire pressure recommendations
Electrical Wiring:
Comprehensive wiring diagrams, component identification, troubleshooting guide
Routine Maintenance:
Oil changes, filter replacements, chain adjustment, spark plug checks, air filter cleaning
Engine Rebuild:
Top-end and bottom-end rebuild procedures, component specifications, torque values
Carburetor Tuning:
Jetting recommendations for various altitudes and conditions, idle speed adjustment
Suspension Servicing:
Fork oil changes, seal replacement, shock absorber servicing
Brake System Maintenance:
Bleeding procedure, pad replacement, caliper service
Troubleshooting:
Diagnosis of common problems, step-by-step solutions for starting issues, performance problems, etc.
Electrical Diagnostics:
Fault finding for ignition, lighting, and charging systems
Depth:
Comprehensive, covering from basic maintenance to complete engine and transmission rebuilds
Illustrations:
Detailed, clear, step-by-step illustrated instructions
Specifications:
Includes critical torque values, clearances, fluid capacities, and electrical specifications
Type:
Constant mesh, 6-speed sequential
Clutch:
Wet, multiple-disc, cable-operated
Gear Ratios:
1st: 2.462, 2nd: 1.750, 3rd: 1.333, 4th: 1.091, 5th: 0.958, 6th: 0.875
Transmission Oil Type:
Yamaha Gear Oil (or equivalent API GL-4, SAE 80)
Transmission Oil Capacity:
1.0 L (1.1 qt)
Engine Oil Change:
Every 10-15 hours of riding or annually
Air Filter Cleaning:
After every few rides, or more frequently in dusty conditions
Spark Plug Inspection:
Every 10-20 hours of riding
Chain Lubrication Adjustment:
Every 5-10 hours of riding
Coolant Type:
Permanent type antifreeze (ethylene glycol based) mixed 50:50 with distilled water
Brake Fluid Type:
DOT 3 or DOT 4 hydraulic brake fluid
Common Wear Items:
Piston rings, clutch plates, suspension seals, wheel bearings, spark plug
Carburetor Jetting Sensitivity:
The VM34SS carburetor can be sensitive to altitude and temperature changes, requiring re-jetting for optimal performance.
Power Valve Maintenance:
The exhaust power valve mechanism can accumulate carbon and require periodic cleaning and adjustment.
