2002 Yamaha YZ250(P)/LC Owner's Service Manual (P/N 5NX-28199-30)

• Official publication and model coverage: Yamaha YZ250(P)/LC Owner's Service Manual, P/N 5NX-28199-30, 1st Edition, June 2001. This 584-page PDF covers the 2002 YZ250P1 (USA), YZ250LC (Europe), and YZ250(P) (Canada, Australia, New Zealand, and South Africa), with market-specific model codes 5NX1, 5NX2, and 5NX4. It contains English, French, German, and Italian text.
• Engine repair coverage: Documents engine removal and installation, crankcase separation, crankshaft and bearing service, constant-mesh transmission and shift-fork work, clutch and primary-drive inspection, kick/shift mechanism service, CDI magneto removal, and water-pump repair.
• Top-end and fuel-system work: Details cylinder-head, cylinder, piston, ring, and YPVS power-valve service; Keihin PWK38S carburetor and reed-valve removal, disassembly, inspection, and assembly; plus factory TPS replacement and adjustment.
• Chassis and brake repair: Carries wheel and bearing work through brake-disc inspection, master-cylinder and caliper teardown, seal replacement, hose installation, fluid filling, and air bleeding. Front-fork disassembly, steering-head bearings, swingarm/linkage service, and rear-shock removal and setup are also included.
• Electrical diagnosis: Provides the full CDI/TPS/solenoid wiring diagram, ignition fault-isolation chart, connector checks, spark-gap testing, coil and CDI-magneto tests, solenoid-valve checks, and TPS input/output-voltage diagnosis.
• Race maintenance and setup: Builds on the competition service schedule and pre-operation checklist with regional carburetor jetting, atmospheric and symptom charts, spark-plug heat-range selection, sprocket combinations, tire setup, and front/rear suspension tuning.
• Illustrated factory reference: Pairs exploded removal views with ordered job charts and follow-on inspection notes. Representative plates cover the piston and power valve, transmission/shift mechanism, brake hydraulics, front fork, and swingarm linkage; component torque data, capacities, wear limits, and electrical test specifications are carried with the related assemblies.

Built for a closed-course competition motorcycle, this is a mechanic-oriented factory repair reference rather than a generic maintenance booklet. It is best suited to race mechanics and experienced owners who are comfortable using pullers, a dial indicator, electrical test equipment, and suspension service tools.

Market-Specific Baselines

The regional identification is carried into the actual service data. European carburetor calibration and jet-needle choices are separated from the USA/Canada/South Africa/Australia/New Zealand settings. Final-drive and chassis baselines group Europe with Canada, while rear-spring specifications and selected fork-assembly notes are called out specifically for Europe. That distinction matters when selecting setup parts or returning a modified bike to its factory baseline.

Repair Detail Beyond Routine Maintenance

The top-end chapter includes A-D cylinder/piston grade matching, clearance and wear inspection, carbon removal, and YPVS linkage alignment. Carburetor coverage preserves the individually set pilot-air-screw reference and includes TPS replacement and recalibration rather than stopping at jet identification.

The manual warns against scraping the aluminum power-valve bore with a sharp tool and against hammering the crankshaft into the cases; either mistake can damage precision surfaces, the crankshaft, or its bearings. It also treats piston-pin clips as one-use parts and shows their required orientation relative to thrust, reducing the risk of a displaced clip damaging the piston and cylinder.

Tools, Diagrams, and Test Data

The special-tool list gives U.S./Canada numbers and 90890-series equivalents. Examples include crankcase splitter YU-1135-A/90890-01135, flywheel puller YM-1189/90890-01189, YU-90050/YM-1277 crankshaft installer components, fork-seal driver YM-01442/90890-01442, and Yamaha pocket tester YU-3112-C/90890-03112.

Beyond the main wiring diagram, the manual supplies cable and hose routing layouts, ignition/solenoid/TPS inspection sequences, piston-to-cylinder matching and carburetor-setting charts, and suspension symptom tables. Torque callouts appear with the assemblies, backed by general fastener and maintenance-specification tables.

Competition Scope and Safety Limits

The electrical section is specific to the race bike's CDI ignition, engine-stop button, solenoid valve, and TPS; it is not a street-equipment wiring manual. Full front-fork disassembly is illustrated, although Yamaha recommends dealer maintenance because the internals are contamination-sensitive. The rear-shock chapter covers removal, spring and bearing work, inspection, adjustment, and installation, but not internal cylinder or reservoir teardown.

Secure the motorcycle on a suitable stand for engine, wheel, brake, or suspension work, and release fork-chamber air before the caps are removed. The rear shock contains high-pressure nitrogen; Yamaha says not to open its cylinder or reservoir and reserves gas-release disposal procedures for dealers.