2005 Yamaha YZ250T / YZ250T1 / YZ250 Owner's Service Manual

This Yamaha owner's service manual covers the 2005 YZ250T competition motocross machine and its regional YZ250T1 and YZ250 versions. The specifications identify model code 1P81 for the US, Canada and South Africa, 1P82 for Europe, and 1P84 for Australia and New Zealand.

Text search, bookmarks and wiring detail: The main manual has searchable text; the cover and separate warning page do not. Embedded bookmarks link to all seven chapters, the contents and wiring diagram. Small wiring labels are readable when enlarged.

• Engine repair: Engine removal, cylinder head and piston inspection, YPVS governor service, crankcase separation, crankshaft installation and internal wear checks.

• Clutch and transmission: Clutch housing, friction plates and primary driven gear inspection; kick axle, shift shaft, shift cam and shift fork service.

• Fuel and cooling: PWK38S Keihin carburetor disassembly, reed valve inspection, radiator pressure testing and water pump repair.

• Chassis and brakes: Wheel and steering head bearing service, swingarm linkage inspection, master cylinder and caliper repair, and brake-system bleeding.

• Suspension service: Telescopic front fork disassembly, seal replacement and damper bleeding; Monocross rear shock removal, spring replacement and damping adjustments.

• Electrical troubleshooting: Wiring diagram, ignition inspection flowchart, CDI magneto and ignition coil tests, plus solenoid valve and throttle position sensor diagnosis.

• Race setup: Carburetor setting charts for weather and track conditions, suspension troubleshooting tables, spring-selection information and alternative sprocket combinations.

The repair sections suit mechanics and experienced owners with the measuring equipment and special tools needed for internal work; Yamaha recommends dealer servicing for the front fork.

Engine Repair and Reassembly

Top-end inspection includes cylinder bore and taper limits, piston-ring clearances and the A–D cylinder/piston matching chart. The matching marks help identify the correct piston for an existing cylinder before reassembly.

Crankcase and transmission procedures cover shaft inspection, shift-fork orientation and operational checks after assembly. The special-tool list identifies crankcase separator YU-1135-A / 90890-01135. Component torque tables cover engine, chassis and ignition fasteners, including the primary-drive-gear bolt and steering-shaft nut.

The YPVS instructions identify a specific damage risk: removing or installing the push-rod bolt without the supplied set pin can damage the power-valve mechanism.

Carburetor Settings and Market Differences

Separate jet-needle sections distinguish N3EJ for the US, Canada, South Africa, Australia and New Zealand from N3EW for Europe. Charts relate atmospheric conditions and throttle opening to carburetor settings, while symptom tables address hesitation, poor acceleration and plug fouling.

The main nozzle is press-fitted and cannot be replaced as a tuning part. The manual instead explains jet-needle selection and adjustment, with setting-part numbers for needles, main jets, pilot jets and power jets.

Ignition, Solenoid and TPS Tests

Electrical diagnosis includes spark-gap testing, ignition-coil resistance checks and separate pickup- and source-coil inspections. Solenoid operation tests and TPS replacement, adjustment and input-voltage checks have their own procedures.

Connector views and wire-color codes accompany the electrical checks. Cable-routing diagrams show the harness, control cables, radiator hoses and front and rear brake hoses.

Brakes, Steering and Suspension

Chassis instructions cover drive and driven sprockets, wheel-bearing replacement and steering-head adjustment. Brake sections include master-cylinder and caliper exploded views, seal inspection and leak checks following bleeding.

Front-fork repair includes damper bleeding and oil-seal installation. The assembly notes explain how allowing the damper assembly to fall into the inner tube can damage the internal valve.

Rear-shock coverage includes spring and bearing replacement, preload, rebound, and low- and high-compression damping adjustments. It does not include internal damper or nitrogen-reservoir rebuilding; the manual warns against dismantling those pressurized parts.

Suspension setting charts connect handling symptoms with front and rear adjustments. Spring rates, identification marks and part numbers support spring selection, while tire-pressure guidance distinguishes muddy, sandy and hard track surfaces.

Cylinder Data and Source-Coil Checks

The cylinder-head specifications distinguish a 21.0 cm³ combustion chamber for the US, Canada, South Africa, Australia and New Zealand from 21.5 cm³ for Europe. Piston-to-cylinder clearance is specified at 0.045–0.050 mm, with a 0.1 mm limit.

For the CDI magneto, source coil 1 is specified at 720–1,080 ohms and source coil 2 at 44–66 ohms, both at 20°C (68°F). The inspection pages pair these ranges with the relevant leads and tester settings.

Printable PDF and Included Pages

Supplied as one printable English PDF. Its 267 pages include 254 pages across the seven chapters and 13 preliminary pages containing the cover, notices, introductory material and contents.