Complete Specification Manual: Yamaha YZ250(S)/LC 1999-2006 Logic-Archive

Architecture-Focus | Unit-Designations | Product-Line

Technical Specifications Reference

Table of Contents Overview

This comprehensive service manual encompasses six major sections covering every operational system and maintenance requirement for Yamaha YZ250(S)/LC models from 1999 through 2006 production cycles. Chapter One establishes general information including model identification, serial number locations, and specification tables. Chapter Two details routine maintenance schedules, fluid capacities, filter replacement intervals, and cable tension adjustments. Chapter Three provides engine disassembly procedures including crankcase separation, piston removal sequences, and bearing inspection methodologies. Chapter Four documents transmission and clutch system architecture, shift mechanism assembly, and drive train component specifications. Chapter Five covers electrical system schematics, charging system testing, and lighting circuit diagrams. Chapter Six consolidates wiring harness routing, connector identification, and complete electrical troubleshooting reference tables.

Engine and Cooling System Documentation

The manual contains exhaustive technical data regarding the liquid-cooled two-stroke engine architecture employed in YZ250(S)/LC models. Detailed specifications define cooling system capacity, thermostat operation parameters, and radiator fin geometry. The documentation includes comprehensive coolant mixture ratios, freeze-protection thresholds, and seasonal maintenance protocols. Flow diagrams illustrate pump operation, bypass valve function, and temperature-regulated circulation patterns. The manual specifies cooling fan activation temperature thresholds and fan motor electrical circuit protection requirements.

Maintenance and Testing Procedures

Complete maintenance documentation covers spark plug selection criteria, electrode gap specifications, and installation torque requirements. The manual provides systematic testing procedures for ignition system performance, including CDI module function verification and spark generation continuity checks. Detailed clearance measurement instructions establish proper methodology for piston-to-cylinder-wall gap verification, ring end-gap measurement, and bearing axial play detection. The documentation includes comprehensive valve timing specifications, rocker arm clearance adjustment procedures, and timing mark identification for crankshaft positioning.

Fastener Security and Assembly Specifications

Throughout the service manual, critical torque specifications establish fastener security standards for all engine components, chassis attachments, and suspension assembly points. The manual designates specific torque values in newton-meters (N·m) and foot-pounds (ft-lbs) for cylinder head fasteners, connecting rod bolts, crankcase fasteners, and frame attachment points. Assembly sequence diagrams illustrate proper fastener installation order to ensure even pressure distribution and component integrity. The documentation includes threadlock compound selection guidance and specifies application points for permanent, removable, and medium-strength adhesive compounds.

Diagnostic and Adjustment Reference

The manual provides systematic diagnostic flowcharts for troubleshooting common operational issues, performance variations, and electrical circuit malfunctions. Adjustment procedures establish proper cable slack measurements, clutch lever engagement points, and throttle response calibration. The documentation includes fuel system schematic diagrams, carburetor float bowl capacity specifications, and needle jet positioning reference tables. Complete electrical troubleshooting sections cross-reference circuit diagrams with specific test point locations and expected voltage measurements at various engine operating conditions.