Yamaha YZ250F(X) 2008 Owner's Service Manual (P/N 5XC-28199-34)

Yamaha's 2008 YZ250F(X) Owner's Service Manual, P/N 5XC-28199-34, is the first edition issued in April 2007. It covers operation, maintenance, repair and tuning for the USA, Canadian, Australian, New Zealand, South African and European competition models.

PDF Search, Bookmarks and Diagram Detail

Search and navigation: The main text is searchable, but valve-pad selection chart values are not. Embedded topic bookmarks provide section access; chapter-level bookmarks open each language's contents page. Small wiring-diagram labels require zooming for clear reading.

One printable, 776-page PDF contains English, French, German and Italian sections. The total includes the front and back covers and five blank pages.

Engine, Chassis and Race-Setup Coverage

The following selected highlights show the service coverage. Further topics include starting and break-in guidance and silencer packing replacement.

• Routine service: Race-based maintenance schedules, pre-operation checks, oil and filter servicing, valve-clearance adjustment and hydraulic brake bleeding.
• Engine repair: Step-by-step engine removal, crankcase separation, cylinder-head and piston inspection, camshaft installation, and transmission and shift-fork service.
• Cooling and lubrication: Radiator and cap pressure checks, water-pump seal and impeller service, oil-pump inspection and oil-strainer cleaning.
• Fuel system: Carburetor disassembly and reassembly, float-height checks, accelerator-pump timing and symptom-based jetting guidance.
• Chassis service: Wheel bearings, brake calipers and master cylinders, front-fork oil seals, steering bearings, swingarm linkage, and rear-shock spring and bearing work.
• Electrical diagnosis: Ignition and throttle-position-sensor troubleshooting workflows, resistance checks, sensor adjustment and the complete wiring diagram.
• Reference illustrations: Exploded assembly views with job instruction charts, lubrication diagrams, cable routing diagrams and valve-pad selection tables.

Written as a mechanic's reference, the manual also explains basic operation for owners. Internal repair and electrical testing call for mechanical experience and the specified tools.

Top-End Inspection and Internal Engine Repair

Component-specific torque tables, inspection limits and special-tool references support repair planning and checking parts before reassembly. The tool list distinguishes US/Canadian tool numbers from those used in other markets.

Valve train: The valve-pad selection tables connect measured clearances with replacement pad numbers. Camshaft coverage adds timing-mark alignment, decompression-mechanism checks and Plastigauge clearance measurement.

The top-end sections warn about valve pads and piston-pin clips falling into the crankcase. The camshaft instructions also identify uneven cap-bolt tightening as a cause of damage to the cylinder head, caps and camshafts.

Clutch and transmission: Inspection distinguishes friction-plate thickness, clutch-plate warpage and release-mechanism condition. Transmission instructions identify gear and shift-fork positions and include checks for smooth operation after assembly.

Carburetor Settings and Throttle Response

Tuning guidance relates main, pilot and leak jets and jet-needle position to throttle opening, atmospheric conditions and running symptoms. Jet and needle part-number tables support selection.

The pilot screw is individually set at the factory, so the printed example is not a universal setting. The accelerator-pump section addresses fuel delivery during rapid throttle opening separately from steady-throttle jetting.

Ignition and Throttle-Position-Sensor Testing

The ignition flowchart separates checks of the engine stop switch, ignition coil, CDI magneto charging and pickup coils, and neutral switch before CDI-unit replacement. This provides a defined fault-isolation path for a no-spark complaint.

Throttle-position-sensor coverage includes variable-resistance checks, input and output voltage testing, and adjustment after replacement. The wiring diagram supplies component references, connector layouts and wire-color codes.

Suspension Setup and Rear-Shock Service Limits

Suspension tuning charts connect handling symptoms with spring, oil-volume and damping settings. European baseline settings are identified separately where applicable.

Rear-shock procedures cover removal, spring replacement and bearing service. Yamaha warns against opening the nitrogen-filled damper cylinder or reservoir; this section should not be read as an internal damper rebuild guide.

Yamaha recommends dealer maintenance for the front fork. Have critical brake and suspension work reviewed by a qualified technician before operation.

A Preview of Engine Clearances and Carburetor Jetting

For top-end inspection, standard camshaft shaft-to-cap clearance is 0.028–0.062 mm, while piston-to-cylinder clearance is 0.030–0.055 mm. These specifications accompany cylinder-head warpage limits, camshaft runout limits and the relevant measurement procedures.

The carburetor specification and tuning sections list a #178 standard main jet for the Keihin FCR-MX37. The tuning charts also document alternative jets for different running conditions.