Yamaha Majesty 400 YP400 Service Manual Set, 2004–2005 (P/N 5RU1-AE1)

Use the supplement together with the base manual for complete service information; it supplies the changes to the earlier procedures and specifications.

Searchable PDFs and Wiring Detail

Search and navigation: Both PDFs support text search. The base manual has working chapter and wiring-diagram bookmarks; the supplement's three section bookmarks all open its contents page. Catalog-return links in both files reference PDFs outside this download. Small labels in the checked wiring diagrams and cable-routing views are readable when enlarged.

ZIP download containing two printable English PDFs, 443 pages total. Original covers, introductory material, and back covers are included, along with six blank pages in the base manual and two in the supplement.

Engine Overhaul, Belt Drive, and FI Diagnosis

These selected workshop topics outline the main repair coverage. Other sections cover body-panel removal and rear brake-lock cable adjustment.

• Engine repair: Engine removal and installation, camshaft and timing-chain work, cylinder-head and valve service, and internal crankshaft, balancer, and transmission work.

• Belt drive and clutch: Primary and secondary sheave removal, inspection and reassembly, clutch-shoe checks, and V-belt installation.

• Brakes and chassis: Wheel and brake-disc service, master-cylinder and caliper overhaul, hydraulic brake bleeding, and front-fork overhaul.

• Cooling system: Radiator and cap pressure tests, thermostat inspection, water-pump seal replacement, and oil-cooler service.

• FI and electrical diagnosis: ECU diagnostic mode, sensor and actuator checks, fault-isolation tables, and circuit troubleshooting for engine and chassis electrical systems.

• Supplement updates: Dual-front-disc service, oil-coated-paper air-filter specifications replacing the base manual's wet-element specification, and revised cable routing.

Yamaha produced these manuals primarily for its dealers and qualified mechanics; they assume basic mechanical knowledge and vehicle repair technique.

Engine Internals and Belt-Drive Service

DOHC single-cylinder engine: Step-by-step procedures cover valve-guide replacement, valve-seat inspection and lapping, piston and ring inspection, and oil-pump service, including its drive chain. Camshaft timing and decompression-system checks accompany the top-end work.

The crankcase sections address crankshaft and balancer assemblies, journal bearings, and final-drive transmission gears. Starter-clutch and generator procedures are also included. Exploded assembly views and job-order charts support the larger disassembly sections.

The supplement provides separate left- and right-hand crankshaft journal-bearing selection tables. These distinctions help match replacement bearings to the applicable crankcase side and specification.

Sheaves and clutch: Detailed checks extend to primary sheave weights, clutch shoes and housing, secondary-sheave bearings and seals, and controlled spring compression. The manual warns against grease contamination of the V-belt and secondary sheave, which can cause drive slippage.

It also cautions against striking crankcase mating surfaces during separation, where damage can compromise the sealing interface.

Chassis, Cooling, and Routine Maintenance

Chassis work extends to static wheel balancing, brake-pad and disc inspection, fork seals, bushings and damper rods, the lower bracket and steering bearings, rear shocks, and the swingarm.

Cooling repair includes water-pump mechanical-seal installation and oil-cooler pipe, cover, and hose inspection. The maintenance chapter adds valve-clearance and exhaust-gas adjustment, compression and ignition-timing checks, engine and transmission oil service, coolant replacement, steering-head adjustment, battery charging, and headlight aiming.

Fuel Injection and Electrical Fault Isolation

The FI chapter locates the ECU, injector, fuel pump, throttle body, throttle-position and intake-pressure sensors, temperature sensors, lean-angle cut-off switch, speed sensor, and ISC valve. Meter-operated diagnostic mode displays sensor output and commands actuators without separate measuring equipment for those functions.

Fault-code, fail-safe, reinstatement, and symptom-based troubleshooting tables guide circuit and component isolation. For example, separate intake-pressure sensor entries distinguish hose faults from open or short circuits. The ISC section specifies throttle-body replacement when valve resistance is outside specification.

Electrical sections cover ignition, the starter cut-off circuit, starter-motor inspection and assembly, A.C. magneto charging, the rectifier/regulator, lights, signals, and radiator-fan control. Immobilizer coverage includes key-code registration, malfunction codes, and registration requirements after ECU, immobilizer-unit, main-switch, or accessory-lock replacement.

Factory Reference Data, Diagrams, and Tools

Engine, chassis, and electrical specifications include general tightening guidance, component torque tables, lubrication and fluid data, wear limits, clearances, adjustment data, and electrical test values.

Diagram examples include the full YP400(S) wiring diagram, FI wiring diagram, cooling-system diagrams, air-induction-system diagrams, electric starting-system circuit diagram, and immobilizer system and circuit diagrams. Cable-routing views locate the wire harness, brake hoses, throttle cables, speed-sensor lead, and charging-system leads.

The special-tool schedule lists Yamaha 90890-series numbers and YM/YU/ACC alternatives for the U.S. and Canada. Examples include sheave spring compressor 90890-04134 with fixed block 90890-04135, fuel-pressure gauge 90890-03153 with adapter 90890-03181, and plane-bearing installer/remover 90890-04146.

Fuel-pressure testing, hydraulic brake work, and spring-loaded clutch service call for trained handling, secure support, and the specified service equipment.

A Preview of Valve-Clearance and Belt-Wear Data

For valve-clearance inspection on a cold engine at room temperature, the base manual specifies 0.15–0.20 mm intake clearance and 0.25–0.30 mm exhaust clearance. Shim-selection tables accompany the adjustment procedures.

In the belt-drive inspection section, specified V-belt width is 30 mm, with a 27 mm service limit. The related checks also supply primary-sheave weight measurements and clutch-shoe wear limits.