The Yamaha YZ426F, produced from 2000 to 2002, represents a significant machine in the evolution of four-stroke motocross motorcycles. As the successor to the YZ400F, this model brought forth a powerful 426cc four-stroke engine, advanced suspension systems, and a lightweight aluminum alloy chassis designed for peak motocross competition performance. Its engineering quality is evident in its robust construction and its contribution to Yamaha's strong racing heritage, making it a notable entry in the competitive off-road market of its era. This comprehensive service manual and parts book provides detailed technical information essential for the maintenance, troubleshooting, and repair of the 2001 Yamaha YZ426F. Covering every aspect from complete engine and transmission overhauls to chassis, brakes, and electrical system diagnostics, it offers step-by-step procedures, specifications, and parts identification. The manual is an indispensable resource for motocross racers, off-road enthusiasts, and mechanics aiming to ensure the optimal performance and longevity of this competition-focused motorcycle. 🏷️ Basic Information Identification Make: Yamaha Model: YZ426F Year: 2001 Generation Generation Designation: First Generation (YZ400F successor) Codes Model Code Usa: 5JG5 Model Code Europe: 5JG6 Model Code Canada Australia New Zealand South Africa: 5JG8 👋 Introduction Market Position Category: Motocross Competition Target Audience: Motocross racers, off-road enthusiasts, mechanics, and Yamaha owners seeking detailed technical information. Competitive Analysis Key Competitors 2001: Honda CRF450R, Kawasaki KX450F, Suzuki RM450Z (though 4-stroke market was nascent). Key Features Vehicle Highlights: Powerful 4-stroke engine, advanced suspension, lightweight chassis, and competitive motocross performance. Manual Value Proposition: Provides essential information for maintaining, troubleshooting, and repairing the YZ426F, ensuring optimal performance and longevity. 📋 Manual Details Coverage Areas Regions Covered: USA, Europe, Canada, Australia, New Zealand, South Africa Page Count Total Pages: 626 Manual Type Manual Type: Service Manual and Parts Book Language Language: English Format Format: PDF Download 📖 Manual Coverage Systems Covered Engine: Complete engine disassembly, inspection, repair, and reassembly. Includes top-end, bottom-end, lubrication, cooling, and valve train. Transmission: Detailed procedures for transmission removal, disassembly, inspection, assembly, and installation. Covers gear selection, clutch operation, and shift linkage. Chassis: Front suspension (forks), rear suspension (shock absorber, linkages), steering system, frame, and subframe. Brakes: Front and rear hydraulic brake systems, including caliper disassembly, piston replacement, brake fluid bleeding, and pad/rotor inspection. Electrical System: Ignition system, lighting, battery, wiring diagrams, component testing, and troubleshooting for electrical faults. Fuel System: Carburetor (Mikuni) specifications, disassembly, cleaning, adjustment, and jetting. Fuel tank and petcock. Exhaust System: Exhaust pipe and silencer inspection, removal, and installation. Wheels And Tires: Wheel bearing inspection and replacement, spoke tensioning, and tire changing procedures. Procedures Included Maintenance Procedures: Oil changes, filter replacement, chain adjustment, spark plug service, air filter cleaning, valve clearance checks, and general lubrication. Troubleshooting: Diagnostic flowcharts and common problem identification for engine performance, electrical issues, and chassis components. Repair Procedures: Step-by-step instructions for rebuilding major components, replacing worn parts, and correcting specific malfunctions. Specifications And Measurements: Torque values for all fasteners, critical clearances, fluid capacities, and performance data. Parts Identification: Detailed parts diagrams with OEM part numbers for ordering replacement components. Technical Depth Depth Of Coverage: Comprehensive, covering routine maintenance to full engine and transmission rebuilds, including electrical diagnostics and suspension tuning. 📊 Manual Specifications File Format File Type: PDF Searchability: Text-searchable PDF Print Quality Print Readability: High resolution for clear printing and viewing Binding Type Binding Method: N/A (PDF Download) Paper Type Paper Quality: N/A (PDF Download) ⚙️ Engine Specifications Primary Engine Engine Type: Four-stroke, liquid-cooled, DOHC, 5-valve Displacement: 426 cc Bore X Stroke: 95.0 mm x 60.0 mm Compression Ratio: 12.6:1 Carburetor: Mikuni TM40SS, Flat-slide, w/TPS Valve Actuation: DOHC, 5 valves per cylinder (3 intake, 2 exhaust) Performance Horsepower Estimate: Approximately 45-50 hp (at crank, varies with tuning and conditions) Torque Estimate: Approximately 30-34 lb-ft (at crank, varies with tuning and conditions) Fuel System Fuel Type: Unleaded gasoline, minimum 91 octane (RON+MON)/2 Fuel Tank Capacity: 2.4 gallons (9.0 Liters) 🔧 Transmission Standard Transmission Type: Constant-mesh 5-speed sequential Optional Optional Gear Ratios: N/A (standard fixed gear ratios) Features Clutch Type: Wet, multi-disc, cable-actuated Final Drive: O-ring sealed chain 📐 Dimensions Exterior Length: 83.7 inches (2125 mm) Width: 32.3 inches (820 mm) Height: 51.0 inches (1295 mm) Wheelbase: 58.1 inches (1475 mm) Ground Clearance: 14.0 inches (355 mm) Weights Dry Weight: 231 lbs (105 kg) Wet Weight Estimate: Approx. 250 lbs (113 kg) with all fluids Seat Height: 39.0 inches (990 mm) 🛡️ Safety Features Ratings Safety Certification: N/A (Off-road competition vehicle) Active Features Braking System Type: Hydraulic disc brakes, front and rear Suspension Design: Upside-down telescopic front forks, Monocross rear suspension with adjustable shock. Passive Features Frame Construction: Aluminum alloy semi-double cradle frame 💡 Technology Features Infotainment Infotainment System: N/A (Pure motocross competition machine, no infotainment features). Driver Assistance Electronic Aids: N/A (No electronic rider aids such as traction control or ABS). Connectivity Connectivity Features: N/A (No connectivity features). 🔧 Maintenance Service Intervals...