Yamaha YZF-R125 Service Manual: Outline of the fi system
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 airfuel 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 (FI) 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 FI system has resulted in a highly precise fuel supply, improved engine response, better fuel economy, and reduced exhaust emissions.
- Engine trouble warning light
- Spark plug
- Ignition coil
- Fuel pump
- FID (fast idle solenoid)
- Throttle body sensor assembly (consisting of throttle position sensor, intake air pressure sensor, intake air temperature sensor)
- ECU (engine control unit)
- Lean angle sensor
- Crankshaft position sensor
- Fuel injector
- Coolant temperature sensor
Features
...
Fi system
The fuel pump delivers fuel to the fuel injector via the fuel filter. The
pressure regulator maintains the
fuel pressure that is applied to the fuel injector at only 250 kPa (2.50 kg/cm²,
36 ...
Other materials:
Installing the shift shaft
1. Install:
Stopper lever "1"
Stopper lever spring "2"
NOTE:
Install the stopper lever spring as shown in the
illustration.
Hook the ends of the stopper lever spring onto
the stopper lever and the crankcase boss "3".
Mesh the stopper lever with the shift drum segment
assembly. ...
Catalytic converters
This vehicle is equipped with catalytic
converters in the exhaust system.
WARNING
The exhaust system is hot after operation.
To prevent a fire hazard or
burns:
Do not park the vehicle near
possible fire hazards such as
grass or other materials that
easily burn.
Park the vehic ...
Setting the diagnostic mode
1. Set the main switch to "OFF" and the engine stop switch to "
".
2. Disconnect the self-diagnosis signal connector "1", and then connect the FI
diagnostic tool "2" as
shown.
3. Disconnect the fuel pump coupler.
4. While pressing the "MODE" button, set the main switch to "ON".
NOTE:
...