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Introduction
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Market Position
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Model Segment:
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Lightweight supersport motorcycle, popular in European markets for its performance and handling in the 125cc class.
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Target Audience:
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Riders seeking a sporty and engaging experience, particularly those new to sportbikes or requiring a smaller displacement machine for licensing or city use.
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Competitive Analysis
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Key Competitors:
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Honda CBR125R, Yamaha YZF-R125 (later models), Cagiva Mito 125, Suzuki GSX-R125 (later models).
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Key Features
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Performance Oriented:
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The RS125 was known for punching above its weight class, offering a potent 2-stroke engine experience.
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Handling Dynamics:
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Premium chassis components and sporty ergonomics contributed to agile and engaging handling.
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Styling:
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Aggressive supersport styling mimicking larger Aprilia race bikes of the era.
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Manual Coverage
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Systems Covered
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Engine Systems:
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Engine overhaul, top-end rebuild, bottom-end inspection, lubrication system, cooling system, fuel system (carburetor tuning and overhaul), exhaust system, ignition system (CDI), starting system.
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Transmission Systems:
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Gearbox disassembly and assembly, clutch operation and adjustment, chain drive maintenance, gear shift mechanism.
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Chassis Systems:
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Frame inspection and repair, front suspension (forks - disassembly, seal replacement, oil levels), rear suspension (shock absorber, linkage system), steering system (headstock bearings), braking system (front and rear caliper overhaul, master cylinder, brake lines, fluid replacement), wheel and tire maintenance, swingarm bearings.
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Electrical Systems:
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Wiring diagrams, lighting system (headlight, taillight, indicators), battery maintenance, charging system (alternator, regulator/rectifier), starter motor circuit, instrument cluster, sensor identification and testing.
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Bodywork:
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Fairing removal and installation, seat, fuel tank, body panel fasteners, decals.
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Procedures Included
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Maintenance Procedures:
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Scheduled maintenance, oil changes, filter replacements (air, fuel), spark plug replacement, chain lubrication and adjustment, brake pad inspection and replacement, coolant flushes, carburetor cleaning and synchronization, fork oil change, battery testing, general cleaning and inspection.
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Troubleshooting Procedures:
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Diagnosis of common engine running issues (hard starting, poor acceleration, misfires), electrical faults, braking problems, suspension noises, cooling system leaks.
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Repair Procedures:
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Engine rebuilds, cylinder head service, piston and ring replacement, crankshaft inspection, gearbox component replacement, clutch assembly service, fork seal replacement, brake caliper overhaul, bearing replacements (swingarm, steering head, wheel), electrical component testing and replacement.
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Diagnostic Procedures:
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Use of diagnostic tools (if applicable for the era), reading spark plug condition, checking compression, inspecting electrical connections, testing ignition components.
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Technical Depth
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Depth Of Coverage:
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Comprehensive. Covers routine maintenance through full engine and component rebuilds. Includes detailed diagrams, specifications, and step-by-step instructions suitable for professional mechanics and experienced DIY enthusiasts.
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Engine Specifications
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Primary Engine
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Engine Manufacturer:
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Rotax
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Engine Displacement:
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124.8 cc
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Engine Configuration:
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Single-cylinder, two-stroke
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Bore X Stroke:
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54 mm x 54.5 mm
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Cooling System:
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Liquid-cooled
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Valvetrain:
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Reed valve induction, Apache rotational reed valve system.
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Performance
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Horsepower Rated:
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Approximately 30-34 HP (varies by market and tuning, some versions slightly lower for licensing).
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Torque Rated:
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Approximately 20-22 Nm
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Top Speed:
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Around 150-160 km/h (93-100 mph)
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Fuel System
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Fuel Delivery:
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Carburetor
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Carburetor Model:
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Dell'Orto PHBH 28 (or similar variant)
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Fuel Type:
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Unleaded gasoline (minimum 95 RON recommended), 2-stroke oil pre-mix or automatic oil injection system.
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Ignition System
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Ignition Type:
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CDI (Capacitor Discharge Ignition)
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Lubrication
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Lubrication Type:
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Pre-mix or automatic oil injection (separate oil tank).
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Maintenance
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Service Intervals
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Oil Change Interval:
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Refer to manual; typically every 3,000-5,000 km or annually for the gearbox oil. Engine oil for 2-strokes is mixed or injected, not changed as a crankcase oil.
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Spark Plug Replacement:
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Refer to manual; typically every 5,000-10,000 km depending on plug type and usage.
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Air Filter Cleaning/Replacement:
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Refer to manual; typically every 3,000-6,000 km.
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Chain Maintenance:
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Lubrication and adjustment recommended every 500-1000 km, or after washing/wet conditions.
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Fluid Specifications
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Coolant Type:
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Ethylene glycol-based antifreeze mixed with distilled water (50/50 ratio recommended). Refer to manual for specific type and capacity.
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2 Stroke Oil Type:
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High-quality synthetic 2-stroke oil (API TC, JASO FD, or better). Refer to manual for specific brand/type recommendations.
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Fork Oil Type:
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Specific weight fork oil (e.g., SAE 5W or 10W). Refer to manual for exact specification and oil level.
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Known Issues
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Carburetor Icing:
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Can occur in cold, humid conditions due to the venturi effect cooling the carburetor body.
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Power Valve Sticking:
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The exhaust power valve can get carboned up and stick, affecting engine performance. Regular cleaning is necessary.
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Cylinder Wear:
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High-performance 2-strokes require diligent maintenance; excessive heat or poor lubrication can lead to accelerated cylinder and piston wear.
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Reed Valve Failure:
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Reed petals can break or wear, impacting engine performance and potentially causing internal damage.
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Electrical Connections:
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Corrosion or loose connections in the wiring harness can lead to intermittent electrical issues.
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