2008 Yamaha YZ450F / YZ450FX Owner's Service Manual

Complete service procedures, troubleshooting guide, and maintenance specifications for Yamaha competition motocross models. Covers engine tuning, suspension setup, carburetor adjustment, and detailed part numbers for 4-stroke dirt bikes.

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Document Details

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Document Number / Seller:
24388 / Carol Thomas
File Size:
22.63 MB
File Type:
PDF
Language:
English, French and German
Pages:
574
Printable:
Yes
Category:
Motorbike
Last updated / verified
Dec 24, 2025

Models Covered & Key Technical Specifications

Yamaha YZ450F & YZ450FX — 2008 Mechanical Industrial Operational Portfolio.

  • Designated Measurement Bounds: 449 cm³ (15.8 Imp oz) is specified as the engine displacement Requirements.
  • Primary Current Rating: The bore and stroke configuration indicates 95.0 × 63.4 mm (3.74 × 2.50 in) Threshold.
  • Advanced Heat Tolerance: Compression ratio of 12.3:1 is configured at maximum combustion chamber pressure Mapping.
  • Defined Weight Data: Tank capacity reaches 7.0 L (1.85 US gal) Parameters measured at standard conditions Configuration.
  • Key Maximum Resolution: Oil capacity delivers 1.2 L (1.27 US qt) total system benchmarks Benchmarks.
  • Essential Alignment Specs: Coolant capacity is designed for 0.99 L (1.05 US qt) complete circuit coverage Range.

Professional Workshop Service Manual & Technical Specifications

Unified Electrical Manual: Motorcycle Yamaha YZ450F & YZ450FX Competition Motocross Owner's Service Manual (2008) Workshop-Compendium

Technical-Scope: YZ450F, YZ450FX (2008) // Calibration-Scope: Systems and subsystems Logic // Operational-Scope: Complete service documentation for 4-stroke competition motocross machines.

Section Coverage Documentation
Engine Systems Cylinder head, valve mechanisms, crankshaft, transmission Complete specifications provided
Suspension & Chassis Front fork, rear shock absorber, steering, swingarm Technical data and adjustment parameters
Electrical & Ignition CDI magneto, spark plug, throttle position sensor Wiring diagrams and system troubleshooting

The documentation is partitioned into General Information, Specifications, Regular Inspection and Adjustments, Engine, Chassis, Electrical, and Tuning chapters, establishing maintenance intervals, disassembling fuel system components, detailing suspension configurations, and documenting electrical component testing procedures.

Precise Threshold

Logically establishing fuel system procedures are documented for carburetor settings, floats, and jet needle configurations. The manual includes complete specifications for the FCR-MX39 Keihin carburetor, pilot screw positioning, and main jet selection across multiple load ranges. Wiring diagrams are provided for ignition coil testing, CDI magneto operation, and throttle position sensor calibration.

Technical Sequences

Adjustment procedures are detailed for engine idling speed, valve clearance measurement at Top Dead Center position, and timing chain tensioner operation. Timing procedures are documented for ignition system verification using timing light equipment. The service manual covers clutch cable free play, hot starter lever adjustment, and brake system bleeding protocols with step-by-step visual aids.

Core Sequences

Technical notes are provided for suspension tuning across front fork oil capacity management (300–375 cm³ extent), rear shock absorber spring preload adjustment using I.D. mark references, and compression/rebound damping force modification through click-based adjuster positioning. The document includes lubrication diagrams for oil delivery pathways, crankshaft bearing surfaces, and camshaft lubrication points.

The manual documents torque specifications for engine components to ensure proper bolt stretch prevention. Each chapter references specialized tools including valve spring compressors, crankshaft installing equipment, and fork seal drivers necessary for proper assembly sequences. Maintenance intervals establish inspection schedules for pre-operation checks, periodic servicing, and race-preparation verification protocols across all mechanical systems.

FAQ

Identify the **correct** spark plug gap specification? keyboard_arrow_down

0.7–0.8 mm (0.028–0.031 in) is the proper gap measurement for the CR8E/NGK resistance-type spark plug to ensure reliable ignition performance.

What procedures are **documented** for coolant system maintenance? keyboard_arrow_down

0.99 L (0.87 Imp qt, 1.05 US qt) total capacity with 50/50 mixing ratio of high-quality ethylene glycol antifreeze and soft water is required for proper cooling system operation and freeze protection.

Determine the **precise** valve clearance specification when engine is cold? keyboard_arrow_down

Intake: 0.10–0.15 mm (0.0039–0.0059 in) and Exhaust: 0.20–0.25 mm (0.0079–0.0098 in) must be maintained for proper combustion chamber sealing and valve operation.

What specifications define **proper** primary electrical coil resistance? keyboard_arrow_down

0.08–0.10 Ω at 20 °C (68 °F) is the standard resistance range for the primary coil in the ignition system to maintain consistent spark generation and engine timing across all operating conditions.

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This manual covers everything you need to know. The download link was sent promptly, and the support team was very helpful when I had questions. Highly recommend!
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The service manual is detailed and easy to understand. I appreciated the quick email response when I needed help with my download. Overall, very satisfied!