Yamaha YFZ450S / YFZ450T / YFZ450V / YFZ450W / YFZ450SEW / YFZ450 Service Manual & Owner's Manual, ATV, years: 2004-2009

Yamaha YFZ450 Series Service Manual & Owner's Manual - 2004-2009

This professional-grade documentation suite provides the technical framework required for the maintenance, overhaul, and precision tuning of high-performance Yamaha sport ATVs. A critical operational safeguard detailed within is the specific throttle override system (T.O.R.S.) calibration, which prevents unintended acceleration by monitoring the mechanical synchronization between the handlebar lever and the carburetor slide.

Technical Applicability & Model Designations

The protocols and specifications in this manual are engineered for the following 439cc and 449cc liquid-cooled chassis configurations:

Initial Production & Engineering Series (2003-2005)

• Yamaha YFZ450S (2003–2004)
• Yamaha YFZ450T (2004–2005)

Mid-Cycle Evolution & Special Editions (2005-2007)

• Yamaha YFZ450V (2005–2006)
• Yamaha YFZ450W (2006–2007)
• Yamaha YFZ450SEW Special Edition (2006–2007)

Late-Model Standardization (2007-2009)

• Yamaha YFZ450 (Unified Series)

Operational ROI & System Integrity

• Maintenance Uptime: Precise service intervals for dry-sump lubrication systems ensure consistent oil pressure and thermal regulation during competitive use.
• Safety Synchronization: Detailed diagnostic procedures for the starting circuit cut-off system protect the electrical architecture and the operator.
• Component Accuracy: Verified exploded diagrams eliminate ambiguity during the disassembly of the constant-mesh 5-speed transmission.

Document Metadata

• Documentation Type: Combined Service Manual & Owner's Manual
• OEM Part Numbers: LIT-11616-17-11 / 5TG-28197-10
• Page Count: 480+ pages
• Language: US English

Technical Depth & Factory Benchmarks

Engine performance is predicated on rigid adherence to factory tolerances, such as the cylinder head warp limit of 0.05 mm (0.002 in). The manual specifies a compression ratio of 11.9:1 for the 439cc variants, requiring premium unleaded gasoline with a minimum pump octane rating of 91 to prevent detonation under high-load operational cycles.

Visual Navigation Aids

• System Architecture: Detailed oil flow and coolant flow diagrams facilitate rapid tracing of pressurized circuits.
• Schematic Mapping: Full-color wiring diagrams for various model years identify the DC-CDI ignition path and the thermo-switch cooling fan logic.
• Precision Exploded Views: Chapter-start diagrams clarify the exact order of component removal for the Keihin FCR39H carburetor and the wet, multiple-disc clutch assembly.

Table of Contents

• General Information: Machine Identification, Special Tools, and Preparation.
• Specifications: Engine, Chassis, Electrical, and Tightening Torques.
• Periodic Checks and Adjustments: Valve Clearance, Idle Speed, and Brake System Bleeding.
• Engine: Overhaul procedures for Camshafts, Cylinder Head, AC Magneto, and Crankcase.
• Cooling System: Radiator, Water Pump, and Thermo-switch Testing.
• Carburetor: Disassembly, Accelerator Pump Timing, and TPS Adjustment.
• Chassis: Wheel Hubs, Rear Axle, Hydraulic Brakes, and Suspension Tuning.
• Electrical: Ignition System, Starting System, and Lighting Diagnostics.
• Troubleshooting: Fault Trees for Hard Starting, Poor Idle, and Handling Instability.

Operational Limits & Specifications

• Cylinder Head Torque: Initial 30 Nm, reset to 20 Nm, then two 90° steps for a final 180° angular tension.
• Valve Clearance (Cold): Intake 0.10–0.15 mm; Exhaust 0.20–0.25 mm.
• Lubricant Specifications: Yamalube 4 (20W-40) or SAE 20W-40; API SE/SF/SG or higher.
• Fluid Capacity: 1.85 L with oil filter replacement; 1.3 L total radiator capacity.
• Drive Chain Slack: 25–35 mm (0.98–1.38 in) measured midway between sprockets.