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Manual Coverage
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Systems Covered
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Engine System:
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Complete overhaul, diagnostics, tuning, lubrication, cooling, exhaust.
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Fuel System:
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Carburetor identification, adjustment, cleaning, fuel tank, fuel lines, petcock.
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Transmission System:
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Gearbox operation, clutch, shift mechanism, lubrication, repair procedures.
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Chassis Frame:
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Frame inspection, alignment, swingarm, pivot bearings, steering head bearings.
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Suspension Front:
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Front fork disassembly, assembly, oil change, seal replacement, spring rates.
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Brakes Front:
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Disc brake caliper servicing, hydraulic lines, master cylinder, pad replacement, bleeding.
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Electrical System:
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Ignition system, lighting, charging system (stator, regulator/rectifier), battery, wiring diagrams.
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Cooling System:
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Air cooling (fins), component checks.
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Exhaust System:
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Muffler, pipe inspection, sealing.
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Wheels Tires:
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Wheel bearing maintenance, spoke tensioning, tire pressure specifications.
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Bodywork Plastics:
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Fairing, fenders, seat, fuel tank removal and installation.
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Suspension Rear
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Rear Shock ABSorber:
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Monoshock unit service, linkage maintenance, damping adjustments.
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Brakes Rear
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Rear Brake System:
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Drum brake inspection, adjustment, shoe replacement.
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Procedures Included
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Routine Maintenance:
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Oil changes, filter replacements, chain adjustment, spark plug checks, air filter cleaning.
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Engine Rebuild:
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Top-end overhaul, piston, rings, cylinder, crankshaft service.
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Carburetor Tuning:
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Jetting, idle speed, mixture adjustments for optimal performance.
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Troubleshooting Diagnostics:
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Systematic fault finding for common and complex issues.
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Wiring Diagrams:
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Detailed electrical schematics for accurate diagnosis and repair.
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Component Disassembly Assembly:
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Step-by-step guides for all major motorcycle components.
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Technical Depth
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Diagnostic Capability:
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Advanced diagnostics and troubleshooting for intricate issues.
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Repair Complexity:
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Covers everything from basic adjustments to complete engine and chassis overhauls.
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Completeness:
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Full factory specification for comprehensive repair and maintenance.
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Engine Specifications
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Primary Engine
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Engine Type:
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Two-Stroke, Single-Cylinder
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Displacement:
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123 cc (7.5 cubic inches)
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Bore X Stroke:
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56.4 mm x 50.0 mm (approximate)
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Compression Ratio:
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Approx. 7.2:1 (varies slightly by model revision)
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Cooling System:
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Forced Air Cooling
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Ignition System:
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CDI (Capacitor Discharge Ignition)
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Spark Plug Type:
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NGK B8ES (or equivalent, consult manual for specific)
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Performance
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Horsepower Estimated:
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Approx. 17-20 HP (at crankshaft, varies by market and tuning)
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Torque Estimated:
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Approx. 14-16 Nm (at crankshaft, varies by market and tuning)
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Fuel System
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Carburetor Model:
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Mikuni VM26SS (typical for this era)
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Fuel Type:
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Unleaded Gasoline (min. 91 RON / 87 AKI recommended)
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Oil Mixture Ratio:
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50:1 (2-stroke oil to gasoline in the oil injection system)
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Maintenance
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Service Intervals
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Engine Oil Change:
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Refer to manual; typically every 2,000-3,000 km or annually. Crankcase oil change is crucial.
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Air Filter Cleaning:
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Check and clean every 1,000-2,000 km, especially in dusty conditions.
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Chain Lubrication Adjustment:
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Lubricate every 500 km, adjust tension as needed according to manual specifications.
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Spark Plug Service:
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Inspect and clean/gap every 3,000-4,000 km, replace as necessary.
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Fluid Specifications
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Transmission Oil Type:
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Yamaha Gear Oil 10W-30 (or equivalent API GL-4 specification)
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Fork Oil Type:
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Yamaha Fork Oil G10 (or equivalent SAE 10W)
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Brake Fluid Type:
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DOT 3 or DOT 4 Hydraulic Brake Fluid
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Known Issues
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Common Wear Items:
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Piston rings, crankshaft seals, clutch plates, and suspension seals are common wear items on high-mileage units.
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Carburetor Performance:
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Carburetors can be sensitive to altitude and air filter condition; regular cleaning and tuning are beneficial.
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Electrical Reliability:
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Older wiring harnesses can develop corrosion or damage, affecting ignition or charging systems. Manual is key for troubleshooting.
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