This manual covers 125 SX, 200 SX, SXS, and MXC models produced between 1999 and 2006. These competition-focused, two-stroke motorcycles are renowned for their high performance, lightweight design, and aggressive power delivery, making them favorites in motocross and off-road racing. The heritage in off-road competition is evident in the engineering of these models, which were continuously refined to deliver peak performance and rider engagement. This comprehensive service and repair manual provides detailed guidance on all aspects of maintaining and troubleshooting these motorcycles. Its scope includes in-depth coverage of engine service and repair, including complete disassembly and reassembly of internal components, as well as maintenance for the cooling system, fuel system, ignition, and exhaust. Additionally, the manual details routine maintenance procedures, engine overhaul, troubleshooting common issues, and component testing, making it an essential resource for owners and technicians seeking to preserve the performance and longevity of their vehicles. 🏷️ Basic Information Identification Make: KTM Model: 125 SX / 200 SX / SXS / MXC Engine Type: Two-Stroke Covered Years: 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Codes Product Code Identifier: KTM125200SX19992006 👋 Introduction Market Position Segment: Competition Motocross / Off-road Target Audience: KTM owners, mechanics, enthusiasts performing engine maintenance and repairs. Competitive Analysis Brand Strength: KTM is renowned for its high-performance, race-bred off-road motorcycles, emphasizing lightweight design and potent engines. Key Features Manual Benefit 1: Enables DIY maintenance and repair, saving on labor costs. Manual Benefit 2: Provides authoritative technical data for accurate diagnostics and component replacement. Manual Benefit 3: Crucial for preserving the performance and longevity of these specialized engines. 📋 Manual Details Coverage Areas Primary Focus: Engine Service and Repair Model Variant Coverage: 125 SX, 200 SX, SXS, MXC Page Count Estimated Page Count: 300-450 pages (typical for comprehensive service manuals) Manual Type Type: Service and Repair Manual Language Language: English Format Format: PDF (Digital Download) 📖 Manual Coverage Systems Covered Engine Mechanical: Complete disassembly, inspection, repair, and reassembly of all internal engine components including cylinder, piston, crankshaft, connecting rod, bearings, seals, gaskets, and cylinder head. Engine Cooling System: Radiator, hoses, thermostat, coolant specifications, and bleeding procedures. Fuel System: Carburetor (Mikuni VM Series typically) overhaul, jetting, float adjustment, fuel lines, and fuel filter replacement. Ignition System: CDI unit, spark plug selection and gap, ignition timing principles, and stator/rotor inspection. Exhaust System: Expansion chamber, silencer maintenance, and gasket replacement. Lubrication System: Premix oil ratios, injection system (if applicable), and general lubrication points. Procedures Included Routine Maintenance: Spark plug replacement, air filter cleaning/replacement, chain adjustment and lubrication, general inspection. Engine Overhaul: Top-end rebuild (piston, rings, cylinder), bottom-end rebuild (crankshaft, bearings, seals), clutch replacement, gearbox maintenance. Troubleshooting: Diagnosis of common engine problems such as starting issues, poor performance, overheating, and abnormal noises. Component Testing: Methods for testing ignition components, carburetor function, and internal engine clearances. Technical Depth Depth: Comprehensive. Covers detailed step-by-step repair procedures, torque specifications, special tool requirements, and diagnostic charts. 📊 Manual Specifications File Format File Type: PDF Searchability: Likely text-searchable PDF for easy navigation. Print Quality Quality Description: High-resolution digital scans, suitable for printing individual pages or the entire manual. Binding Type Binding For Printed Version: Not applicable (Digital PDF) Paper Type Paper Type For Printed Version: Not applicable (Digital PDF) ⚙️ Engine Specifications Primary Engine Engine Type: Liquid-cooled, two-stroke single-cylinder Bore X Stroke 125: Approximately 54 mm x 54.5 mm (varies slightly by sub-model and year) Bore X Stroke 200: Approximately 64 mm x 60 mm (varies slightly by sub-model and year) Displacement 125: 124.9 cc (approximate) Displacement 200: 193 cc (approximate) Reed Valve Intake: Standard feature for two-stroke performance tuning. Power Valve: KTM's patented Power-Jet system and exhaust power valve for improved torque and powerband. Performance Horsepower 125: Approximately 30-35 HP (varies by model variant and tuning) Horsepower 200: Approximately 35-40 HP (varies by model variant and tuning) Torque Figures: Specific torque figures vary but are optimized for explosive acceleration in the mid-to-high RPM range. Fuel System Carburetor Type: Mikuni VM Series (e.g., VM28 for 125, VM34 for 200 - specific models may vary) Fuel Type: Unleaded gasoline with 2-stroke oil premix. Recommended octane rating typically 91-95 (RON+MON)/2. Premix Ratio: Typically 50:1 or 60:1 (refer to manual for exact specification based on oil type). 🔧 Transmission Standard Type: 6-speed manual constant mesh gearbox. Optional Availability: Not applicable for these models. Features Clutch Type: Hydraulically operated multi-plate wet clutch. Gear Ratios: Specific gear ratios are detailed within the manual, optimized for motocross performance. Transmission Oil Type: API GL-4 or GL-5, SAE 75W/90 or 10W/40 motorcycle-specific gearbox oil (refer to manual for exact specification). 📐 Dimensions Exterior Wheelbase: Approximately 1440-1460 mm (125/200 models vary slightly) Weights Dry Weight: Approximately 90-95 kg (125/200 models vary slightly) Fuel Tank Capacity: Approximately 7-9 liters (models vary) 🛡️ Safety Features Ratings Crash Test Ratings: Not applicable for off-road competition motorcycles. Active Features...