2008 Yamaha YP400X Majesty Service & Repair Manual (P/N LIT-11616-21–34)

• Yamaha factory publication P/N LIT-11616-21-34, manual No. 5RU-28197-11, first edition May 2007, for the 2008 YP400X Majesty, model 5RUT.
• Covers engine removal and installation, camshaft and timing-chain service, cylinder-head and valve work, piston and cylinder inspection, crankcase separation, crankshaft and balancer-shaft bearing work, oil-pump service, starter-clutch service, and final transmission assembly.
• Details V-belt automatic transmission repair, including primary and secondary sheave removal, clutch and belt inspection, spring-compressor procedures, sheave reassembly, and V-belt installation.
• Includes front and rear wheel service, brake-caliper and master-cylinder disassembly and assembly, hydraulic bleeding, handlebar service, fork overhaul, steering-head work, rear-shock service, and rear-arm inspection.
• Covers radiator, thermostat, water-pump, fuel-tank and fuel-pump service, injector and throttle-body checks, pressure-regulator operation, throttle-position sensor checks, and air-induction diagnosis.
• Provides ignition, starting, charging, lighting, signaling, cooling-fan, and FI circuit diagrams, plus ECU self-diagnosis, fail-safe tables, diagnostic-monitoring tests, fault-code troubleshooting, cable-routing views, and the full 2008 wiring diagram.
• Lists Yamaha special tools and tool numbers for engine, CVT, fork, cooling, fuel-pressure, and electrical work, together with component-specific torque tables, lubrication points, capacities, clearances, wear limits, and electrical test specifications.

Operational Documentation

This 343-page PDF identifies a 395 cc liquid-cooled four-stroke DOHC single-cylinder engine with electronic fuel injection, electric starting, and a centrifugal V-belt automatic transmission. Key build identifiers include the 5RU31/Yamaha ECU, AISAN throttle body marked 5RUT 30, 5RU/AISAN fuel pump, and SM-13/MITSUBA starter motor. Those identifiers help match the covered configuration before repair or parts selection.

The manual contains factory repair procedures, not just a catalog of settings. Exploded assembly views open the removal and disassembly sections, followed by job charts that identify parts, work order, replacement items, lubrication points, and related torque data. The engine chapters cover camshaft timing, cylinder-head and valve service, piston and cylinder inspection, crankcase separation, crankshaft journal-bearing selection, balancer-shaft installation, oil-pump work, starter-motor repair, and internal transmission checks.

Periodic maintenance coverage includes valve-clearance adjustment, idle and throttle-cable checks, ignition timing and compression testing, engine and final-transmission oil service, air-filter and V-belt-case filter work, fuel-line inspection, cooling-system checks, coolant replacement, brake inspection and bleeding, steering-head adjustment, fork checks, wheel and tire inspection, battery service, fuse checks, and headlight adjustment.

FI, Electrical, and Troubleshooting Coverage

The fuel-injection material follows the system from component layout through fault isolation. The FI diagrams identify the ECU, injection-system relay, fuel pump and injector, ISC valve, throttle-position sensor, intake-air pressure and temperature sensors, coolant-temperature sensor, crankshaft-position sensor, lean-angle sensor, ignition coil, and related warning-light and meter circuits. Fuel-system repair sections add fuel-tank and pump removal, fuel-hose installation, injector checks, throttle-body inspection, pressure-regulator testing, throttle-position sensor checks, and air-induction diagnosis.

The electrical chapter provides separate circuit diagrams and troubleshooting paths for ignition, electric starting and the starting circuit cut-off system, charging, lighting, signaling, and radiator-fan control. FI diagnosis includes ECU self-diagnostic operation, fail-safe behavior, fault-code and diagnostic-monitoring tables, sensor readings, actuator checks, malfunction-history handling, and code-specific troubleshooting. The electrical component section adds switch, relay, ignition, charging, sensor, fan-motor, and V-belt reset coupler tests.

Named visual references include Outline of the FI System, Cooling System Diagrams, Cable Routing, Starting Circuit Cut-off System Operation, the Fuel Injection System - Circuit Diagram, and the 2008 YP400X Wiring Diagram. A separate troubleshooting chapter addresses hard starting, incorrect idle, poor medium- and high-speed performance, overheating or overcooling, clutch faults, weak braking, fork problems, unstable handling, and lighting or signaling failures.

Reference Data and Technical Specifications

Factory reference data is organized by assembly. Engine, chassis, and electrical specification tables are backed by dedicated engine and chassis torque sections, lubrication charts, cooling-system diagrams, cable-routing drawings, maintenance schedules, capacities, inspection limits, bearing clearances, valve data, brake and suspension specifications, and multimeter test values.

The special-tool section gives both Yamaha international and U.S./Canada tool numbers where applicable. Examples include the sheave spring compressor 90890-04134 / YM-04134, radiator cap tester 90890-01325 / YU-24460-01, fuel-pressure gauge 90890-03153 with adapter 90890-03181, valve spring compressor 90890-04019 / YM-04019, and fork-seal driver components 90890-01367 and 90890-01381. These references matter because several repair operations are designed around the listed holders, pullers, compressors, drivers, and test equipment.

Several manual-specific cautions are easy to miss during repair. The camshaft section warns against rotating the crankshaft during camshaft installation and requires the caps to be tightened evenly; ignoring those points can upset valve timing or damage the cylinder head, caps, and camshafts. During CVT work, grease must be kept off the V-belt and sheave surfaces, and the spring-loaded secondary sheave is handled with the specified compressor and fixed block. Front-fork separation is another damage point: excessive force can ruin the oil seal and bushings, while bottoming the inner tube can damage the oil-flow stopper.

The publication is written for Yamaha dealers and qualified mechanics and assumes a working knowledge of motorcycle repair. Fuel-system, hydraulic-brake, battery, and spring-loaded CVT work should be carried out with suitable vehicle support, electrical isolation, and the specified tools.