2001 Yamaha YZ-125 Service Manual

2001 Yamaha YZ-125 Service Manual

This 2001 Yamaha YZ-125 Service Manual is intended as a handy, easy-to-read reference book for the mechanic. Comprehensive explanations of all installation, removal, disassembly, assembly, repair, electrical system, and check procedures are laid out with the individual steps in sequential order. The main function of a fuel supply system is to provide fuel to the combustion chamber at the optimum air-fuel ratio in accordance with the engine operating conditions and the atmospheric temperature. In the conventional carburetor system, the air-fuel ratio of the mixture that is supplied to the combustion chamber is created by the volume of the intake air and the fuel that is metered by the jet used in the respective carburetor.

Despite the same volume of intake air, the fuel volume requirement varies by the engine operating conditions, such as acceleration, deceleration, or operating under a heavy load. Carburetors that meter the fuel through the use of jets have been provided with various auxiliary devices so that an optimum air-fuel ratio can be achieved to accommodate the constant changes in the operating conditions of the engine.

As the requirements for the engine to deliver more performance and cleaner exhaust gases increase, it becomes necessary to control the air-fuel ratio in a more precise and finely tuned manner. To accommodate this need, this model has adopted an electronically controlled fuel injection (Fl) system, in place of the conventional carburetor system. This system can achieve an optimum air-fuel ratio required by the engine at all times by using a microprocessor that regulates the fuel injection volume according to the engine operating conditions detected by various sensors. The adoption of the Fl system has resulted in a highly precise fuel supply, improved engine response, better fuel economy, and reduced exhaust emissions.

2001 Yamaha YZ-125 Service Manual table of contents

• General Information 2001 Yamaha YZ-125 Service Manual
  Identification, features, important information, basic service information, special tools.
• Specifications
  General specifications, engine specifications, chassis specifications, electrical specification, tightening torques, lubrication points, and lubricant types, lubrication system chart, and diagrams, cooling system diagrams, cable routing.
• Periodic Checks And Adjustments
  Periodic maintenance.
• Chassis
  General chassis, front wheel, rear wheel, front brake, rear brake, handlebar, front fork, steering head, rear shock absorber assembly, swingarm, chain drive.
• Engine
  Engine inspection, engine removal, camshafts, cylinder head, valves and valve springs, generator and starter clutch, electrical starter, clutch, shift shaft, oil pump, oil pan, crankcase, connecting rods and pistons, crankshaft and balancer shaft, transmission.
• Cooling System
  Radiator, oil cooler, thermostat, water pump.
• Fuel System
  Fuel tank, Throttle bodies, air induction system.
• Electrical System
  Ignition system, electric starting system, charging system, lighting system, signaling system, cooling system, fuel injection system, fuel pump system, electrical components.
• Troubleshooting
  Self-diagnostic function and diagnostic code table, event code table.

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