2008 Yamaha WR250F / WR250FX Owner's Service Manual (P/N 5UM-28199-71)

Yamaha's 2008 WR250F(X) Owner's Service Manual, document 5UM-28199-71 (first edition, July 2007), covers the WR250FX and WR250F market variants listed above. Its seven chapters progress from operation and regular inspection to tuning and workshop repair.

• Engine and transmission: Engine removal, crankcase separation, cylinder-head and piston inspection, valve adjustment, clutch repair, and transmission disassembly and reassembly.

• Carburetor tuning: Keihin FCR-MX37 overhaul, float-height checks, accelerator-pump timing adjustment, and symptom-based jetting guidance.

• Cooling and lubrication: Radiator and cap pressure tests, water-pump shaft and seal replacement, oil-pump inspection, and oil-circuit diagrams.

• Chassis service: Front-fork rebuilding, steering and wheel-bearing service, brake caliper and master-cylinder repair, swingarm linkage work, and rear-shock spring replacement.

• Electrical diagnosis: Ignition, starting, charging, lighting, throttle-position sensor, and speedometer fault charts, plus starter-motor disassembly and inspection.

• Workshop reference: Component torque tables, cable-routing drawings, valve-pad selection tables, and exploded assembly views with job instruction charts.

Owners can use the operation and maintenance sections; the internal repair procedures are suited to mechanics equipped for precision measurement and the specified service tools.

Maintenance and Internal Engine Repair

General sections cover machine identification, control functions, and multi-function display settings. Maintenance charts address competition use, while oil-service instructions distinguish routine oil changes from filter replacement.

Valve train: Camshaft and decompression-system checks accompany valve, guide, seat, and spring inspection. The pad-selection tables connect measured clearance with the installed shim, helping a mechanic identify the replacement pad needed for valve adjustment.

Uneven cam-cap tightening can damage the cylinder head, caps, or camshafts; the assembly section explains the relevant precautions.

Bottom end: Crankshaft measurements, gear-dog and shift-fork inspections, and clutch wear limits support internal repair decisions. Separate procedures cover the kick shaft, shift shaft, balancer, AC magneto, and starter clutch, including one-way clutch operation checks.

The special-tool list identifies the crankcase separating tool as YU-1135-A for USA/CDN and 90890-01135 for other markets.

Fuel-System Tuning and Water-Pump Service

The carburetor chapter covers the needle valve, float, starter plungers, air-cut valve, and accelerator-pump diaphragm. Tuning guidance relates throttle response to the main jet, pilot jet, jet needle, and leak jet; the symptom chart also directs attention to fuel restrictions and air-filter condition.

Air-induction system testing includes air cut-off valve checks using a vacuum/pressure pump. Water-pump inspection covers the impeller, shaft, bearing, and seals; incorrect shaft installation can damage a seal lip or dislodge its spring.

Suspension, Steering and Brakes

Front-fork procedures cover the damper rod, base valve, bushings, seals, bleeding, and oil-level setting. Yamaha recommends dealer maintenance for this assembly. The listed fork seal driver is YM-A0948 / 90890-01502.

Suspension setting charts relate handling symptoms to spring choice and damping adjustments. Rear-spring preload settings distinguish USA/CDN from AUS/NZ/ZA specifications.

Rear-shock scope: Removal, spring and bearing replacement, inspection, and external adjustment are covered. The pressurized nitrogen cylinder and reservoir are not intended for disassembly; Yamaha's handling warnings apply.

Brake coverage includes caliper pistons and seals, master-cylinder components, and hydraulic bleeding. Steering-bearing and swingarm-linkage procedures provide installation details beyond routine lubrication.

Electrical Fault Tracing

The ignition and starting charts distinguish a no-spark condition from a starter that will not turn. The starting-circuit cut-off diagram shows the clutch-switch and neutral-switch paths, helping separate an interlock fault from starter-motor trouble.

Charging, lighting, throttle-position sensor, and speedometer tests include connection views and meter specifications. Starter-motor inspection covers the armature, commutator, and brushes. The main wiring diagram marks USA and non-USA differences and includes wire-color codes.

Selected Cylinder-Head and Ignition Specifications

Cylinder head: Cold valve clearance is 0.10–0.15 mm for the intake valves and 0.17–0.22 mm for the exhaust valves. The cylinder-head warpage limit is 0.05 mm.

Ignition pickup: The AC magneto test specifies 248–372 Ω at 20 °C (68 °F) across the red and white leads, with connection illustrations accompanying the test.

PDF Search, Bookmarks and Included Pages

Search and diagram detail: Main text is searchable, with embedded bookmarks for chapters and sections. Some chart and diagram labels are not searchable. Small labels in the main wiring diagram are readable when enlarged.

Supplied as one printable, English-language, 222-page PDF. This total includes the front and back covers, preliminary pages, and three unnumbered blank pages; no separate supplement is included.