2002 Yamaha YZ250(R)/LC Service Manual (P/N 5UP-28199-30)

This 583-page official Yamaha publication (P/N 5UP-28199-30) serves as the primary technical resource for the 5UP-series build. It comprehensively documents all internal components and chassis assemblies for the 2002 YZ250(R) and YZ250LC motocross motorcycles.

Supplied as a comprehensive PDF file, this manual provides direct access to factory-level YPVS procedures and Keihin PWK38S data right at the workbench. Having these precise parameters on hand ensures accurate rebuilding and prevents costly bottom-end damage, effectively reducing lift downtime in the shop.

Component and Systems Documentation Designed for deep-dive diagnostics and routine maintenance, the manual includes a dedicated 105 pages strictly focusing on detailed torque-check points, electrical wiring diagrams, and component-specific maintenance procedures. To support these tasks, visual aids like exploded diagrams, cable routing diagrams, job instruction charts, tuning charts, and sectional views are prominently featured. It outlines exact maintenance intervals, carburetor jetting setups, and suspension parameters. You will find complete coverage of engine assembly, transmission procedures, and exact torque sequences for the frame, engine mounts, and control assemblies. It also provides step-by-step repair instructions for tasks that usually require an expensive trip to the dealer:

• Executing complete bottom-end crankcase splitting
• Rebuilding the high-pressure rear shock absorber
• Overhauling the telescopic front forks
• Bleeding the hydraulic brake system
• Adjusting the Yamaha Power Valve System linkage
• Swapping out worn clutch friction plates
• Tuning the Keihin carburetor

Crucial chassis and engine sub-assemblies covered include:

• CDI magneto stator and rotor
• Water pump impeller housing
• Shift cam and selector forks
• Primary drive gear mechanism
• Kick starter ratchet wheel
• Steering head bearings
• Reed valve block

Specification Highlights and Reference Data The documentation provides significant technical depth through extensive reference tables, ensuring absolute precision during engine assembly. Critical measurements include:

• Piston-to-cylinder clearance: 0.045–0.050 mm
• Clutch housing radial clearance: 0.030–0.055 mm
• Cylinder head nut torque: 25 Nm (18 ft-lb)

When performing a major repair on the 2002 YZ250, technicians must navigate a few model-specific traps. For instance, extracting the push rod without inserting the mandatory set pin will immediately damage the delicate YPVS components. Additionally, during front fork reassembly, the inner tube must be held aslant; if kept perfectly vertical, the damper rod can drop rapidly and shatter the internal base valve.

Electrical troubleshooting is equally precise. The ignition timing is strictly set at 0.18 mm B.T.D.C., and the CDI source coil 1 resistance is documented to measure between 720–1,080 ohms at 20°C. Note that intake valve clearance is not applicable for this 2-stroke power unit.

Note: Working on high-performance competition motorcycles involves handling pressurized systems and highly flammable fluids. Always review the pre-operation checks and general safety sections provided in the introductory chapters before beginning any teardown or chassis adjustment.