This manual covers the 450 EXC, 400 EXC, and 520 SX models from the production years 2000 through 2003. These high-performance off-road motorcycles are powered by the robust LC4 engine family, available in 400cc, 450cc, and 520cc displacements. Renowned for their powerful engines, lightweight chassis, and aggressive off-road performance, these motorcycles cater to competitive riders and serious enthusiasts. They have a strong heritage in motorsports, validating their capabilities in demanding conditions, and are manufactured in Austria. This comprehensive service and repair manual provides detailed guidance for engine service and repair. It covers engine mechanicals, lubrication, cooling systems, fuel systems, ignition systems, and exhaust systems. The manual includes procedures for preventative maintenance, systematic troubleshooting, engine rebuilds, carburetor adjustments, and valve adjustments. It is designed to assist owners, mechanics, and technicians in maintaining and repairing these vehicles, offering advanced diagnostics and detailed repair complexity suitable for a wide range of skill levels. 🏷️ Basic Information Identification Make: KTM Model: 450 EXC, 400 EXC, 520 SX Years Covered: 2000, 2001, 2002, 2003 Codes Engine Codes: LC4 (specific variations apply across models) 👋 Introduction Market Position Vehicle Segment: High-performance off-road motorcycles (Enduro and Motocross/Supercross variants). Competitive Analysis Key Competitors: Yamaha WR/YZ series, Honda CRF/XR series, Suzuki RM/DR series, Kawasaki KX/KLX series. Key Features Vehicle Appeal: Renowned for powerful engines, lightweight chassis, and aggressive off-road performance, catering to competitive riders and serious enthusiasts. 📋 Manual Details Coverage Areas Manual Coverage Scope: Engine Service and Repair Page Count Estimated Page Count: 150-250 (typical for this type of manual) Manual Type Manual Classification: Service/Repair Manual Language Language Support: English Format Delivery Format: PDF 📖 Manual Coverage Systems Covered Engine Mechanical: Detailed disassembly, inspection, repair, and reassembly of all internal engine components, including cylinder head, valves, pistons, connecting rods, crankshaft, and timing system. Engine Lubrication: Oil pump operation, oil cooler service (if applicable), oil filter replacement, lubrication points, and oil capacities. Cooling System: Radiator service, coolant replacement, water pump inspection and repair, thermostat testing, and hose inspection. Fuel System: Carburetor (Mikuni models common) overhaul, adjustment, and troubleshooting. Fuel pump (if applicable) inspection and replacement. Fuel filter service. Ignition System: Ignition coil testing, spark plug specifications, CDI unit testing (if applicable), and stator/rotor inspection. Exhaust System: Exhaust pipe and muffler inspection, mounting, and potential repair guidance. Procedures Included Preventative Maintenance: Regular service checks, fluid changes, filter replacements, spark plug maintenance, and general inspection guidelines. Troubleshooting: Systematic diagnostic procedures for common engine performance issues, starting problems, and unusual noises. Engine Rebuild: Complete step-by-step instructions for engine overhaul, including torque specifications, bearing clearances, and ring gap measurements. Carburetor Adjustment: Detailed guidance on adjusting idle speed, air-fuel mixture, and jetting for optimal performance. Valve Adjustment: Procedures for checking and adjusting valve clearances. Technical Depth Diagnostic Level: Advanced diagnostics, including electrical system testing and component-specific fault finding. Repair Complexity: Covers both basic repairs and complete engine rebuilds, suitable for experienced DIY mechanics and professional technicians. 📊 Manual Specifications File Format PDF Searchability: Searchable text within PDF for quick information retrieval. Print Quality Document Resolution: High-resolution scans ensuring clarity of diagrams and text. Binding Type Digital Binding: N/A (Digital PDF format) Paper Type Digital Paper Type: N/A (Digital PDF format) ⚙️ Engine Specifications Primary Engine Engine Type: Four-stroke, liquid-cooled, single-cylinder (LC4 engine family). Engine Displacement: 400cc, 450cc, 520cc (variant dependent). Performance Horsepower Range: Approximately 40-55 HP (model and year specific, unconfirmed without exact VIN). Torque Range: Approximately 35-45 lb-ft (model and year specific, unconfirmed without exact VIN). Fuel System Carburetor Type: Mikuni VM series or similar performance carburetors (e.g., TM40, TM42). 🔧 Transmission Standard Transmission Type: 5-speed or 6-speed manual transmission (model dependent). Optional Transmission Options: N/A (Manual transmission standard for these models). Features Clutch Type: Hydraulically operated wet multi-plate clutch. 📐 Dimensions Exterior Wheelbase Range: Approx. 1470-1500 mm (model dependent). Weights Dry Weight Range: Approx. 110-120 kg (model dependent). 🛡️ Safety Features Ratings Safety Certification: Off-road use vehicles; typically not subjected to NHTSA or Euro NCAP crash ratings. Active Features Braking System: Hydraulic disc brakes front and rear. Specific caliper and rotor sizes vary by model. Passive Features Protective Gear Recommendation: Manual will implicitly recommend proper maintenance for safe operation; rider is responsible for protective gear. 💡 Technology Features Infotainment Dashboard Display: Basic digital or analog instrumentation (speedometer, tachometer, hour meter, indicator lights). No infotainment systems present. Driver Assistance ABS Availability: ABS was not typically an option or standard on these performance off-road models during this era. Connectivity Connectivity Features: N/A (No electronic connectivity features). 🔧 Maintenance Service Intervals Oil Change Interval: Typically every 15-25 operating hours or annually, depending on usage severity. Refer to manual for precise intervals. Air Filter Cleaning: Recommended every 5-10 operating hours or as needed based on conditions. Valve Check Interval: Approximately every 20-30 operating hours for optimal performance. Fluid Specifications Engine Oil Type: High-quality synthetic motorcycle oil...