Yamaha 2004 YP400 User Manual (English)

Joseph OliverJul 27, 2025

What to do if Yamaha 2004 YP400 engine operation is not normal?

R
Robert GardnerJul 27, 2025
If the engine operation is not normal or the engine trouble warning light is on, you should first check the fault code number displayed on the meter. Then, check the operation of the throttle position sensor (throttle angle), ignition coil, and fuel injector in the diagnostic mode. Identify the system with the malfunction using the 'FAIL-SAFE ACTIONS TABLE' and the probable cause using the 'Fault code table'. If a defective sensor or actuator is the cause, check and repair it. Monitor the sensors and actuators in the diagnostic mode, and perform ECU reinstatement. Finally, check the engine condition and erase the malfunction history in the diagnostic mode.

Yamaha 2004 YP400 Specifications

General

Year	2004
Manufacturer	Yamaha
Model	YP400
Category	Scooter
Displacement	395 cc
Fuel System	Fuel injection
Ignition	Digital TCI
Starter	Electric
Transmission	Automatic
Final Drive	V-Belt
Front Suspension	Telescopic fork
Rear Suspension	Unit swing
Rear Brake	Single disc
Front Tire	120/80-14
Rear Tire	150/70-13
Wheelbase	1, 590 mm
Bore x Stroke	83 mm x 73 mm
Front Brake	Dual discs
Width	775mm
Fuel Capacity	14.0 litres (3.7 US gallons)

Summary

SPECIFICATIONS

ENGINE SPECIFICATIONS

Detailed engine type, displacement, bore, stroke, fuel, oil, and transmission specs.

TIGHTENING TORQUES

Specific torque values for engine and chassis fasteners with detailed item lists.

PERIODIC CHECKS AND ADJUSTMENTS

PERIODIC MAINTENANCE AND LUBRICATION CHART

Schedule of checks and maintenance jobs based on odometer reading and annual service.

ENGINE

Checks and adjustments for valve clearance, exhaust gas volume, idling speed, and spark plug.

CHASSIS

FRONT WHEEL AND BRAKE DISC

Procedures for removing, checking, installing, and balancing the front wheel and brake disc.

REAR WHEEL AND BRAKE DISC

Procedures for removing, checking, and adjusting the static balance of the rear wheel.

FRONT AND REAR BRAKES

Replacing brake pads, checking hoses, bleeding systems, and inspecting master cylinders and calipers.

FRONT FORK

Procedures for removing, disassembling, checking, and installing front fork legs.

STEERING HEAD

Procedures for removing, checking, adjusting, and installing the steering head components.

REAR SHOCK ABSORBER ASSEMBLIES AND SWINGARM

Procedures for removing, checking, and installing rear shock absorbers and the swingarm.

ENGINE

ENGINE REMOVAL

Steps for removing leads, hoses, exhaust pipe, muffler, and the entire engine assembly.

CAMSHAFTS

Procedures for removing, checking, and installing camshafts, sprockets, and related components.

CYLINDER HEAD

Procedures for removing, checking, and installing the cylinder head, gasket, and timing chain guide.

VALVES AND VALVE SPRINGS

Procedures for removing, checking, and installing valves, springs, guides, seats, and lifters.

CYLINDER AND PISTON

Procedures for removing, checking, and installing the piston, rings, cylinder, and related parts.

BELT DRIVE

Procedures for removing, checking, assembling, and installing V-belt, sheaves, weights, and clutch components.

STARTER CLUTCH AND GENERATOR

Procedures for removing, checking, installing, and assembling the starter clutch and generator components.

OIL PUMP

Procedures for checking, assembling, and installing the oil pump and drive chain.

Yamaha 2004 YP400 User Manual

Table of Contents

Questions and Answers:

Yamaha 2004 YP400 Specifications

Summary

SPECIFICATIONS

ENGINE SPECIFICATIONS

TIGHTENING TORQUES

PERIODIC CHECKS AND ADJUSTMENTS

PERIODIC MAINTENANCE AND LUBRICATION CHART

ENGINE

CHASSIS

FRONT WHEEL AND BRAKE DISC

REAR WHEEL AND BRAKE DISC

FRONT AND REAR BRAKES

FRONT FORK

STEERING HEAD

REAR SHOCK ABSORBER ASSEMBLIES AND SWINGARM

ENGINE

ENGINE REMOVAL

CAMSHAFTS

CYLINDER HEAD

VALVES AND VALVE SPRINGS

CYLINDER AND PISTON

BELT DRIVE

STARTER CLUTCH AND GENERATOR

OIL PUMP

CRANKSHAFT

TRANSMISSION

COOLING SYSTEM

RADIATOR

THERMOSTAT

WATER PUMP AND OIL COOLER

FUEL INJECTION SYSTEM

TROUBLESHOOTING CHART

THROTTLE BODY AND FUEL INJECTOR

ELECTRICAL SYSTEM

IGNITION SYSTEM

ELECTRIC STARTING SYSTEM

STARTER MOTOR

CHARGING SYSTEM

LIGHTING SYSTEM

SIGNALING SYSTEM

COOLING SYSTEM

IMMOBILIZER SYSTEM

TROUBLESHOOTING

STARTING FAILURE/HARD STARTING

FAULTY CLUTCH

OVERHEATING

POOR BRAKING PERFORMANCE

FAULTY FRONT FORK LEGS

UNSTABLE HANDLING

FAULTY LIGHTING OR SIGNALING SYSTEM

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