Yamaha YZF-R125 Service Manual: 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, 36.3 psi). Accordingly, when the energizing signal from the ECU energizes the fuel injector, the fuel passage opens, causing the fuel to be injected into the intake manifold only during the time the passage remains open. Therefore, the longer the length of time the fuel injector is energized (injection duration), the greater the volume of fuel that is supplied. Conversely, the shorter the length of time the fuel injector is energized (injection duration), the lesser the volume of fuel that is supplied.
The injection duration and the injection timing are controlled by the ECU. Signals that are input from the throttle position sensor, crankshaft position sensor, intake air pressure sensor, intake air temperature sensor, lean angle sensor and coolant temperature sensor enable the ECU to determine the injection duration. The injection timing is determined through the signals from the crankshaft position sensor. As a result, the volume of fuel that is required by the engine can be supplied at all times in accordance with the driving conditions.
- Fuel pump
- Fuel injector
- Ignition coil
- Coolant temperature sensor
- ECU (engine control unit)
- Lean angle sensor
- Crankshaft position sensor
- FID (fast idle solenoid)
- Air filter case
- Throttle body
- Throttle body sensor assembly
- Intake air temperature sensor
- Throttle position sensor
- Intake air pressure sensor
- Fuel system
- Air system
- Control system
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 tempera ...
Multi-function display
1. Multi-function display
2. "RESET/SELECT" button
The multi-function display is equipped with the
following:
a speedometer (which shows the riding speed)
an odometer (which shows the t ...
Other materials:
Coolant
The coolant level should be checked
before each ride. In addition, the coolant
must be changed at the intervals
specified in the periodic maintenance
and lubrication chart.
To check the coolant level
Place the vehicle on a level surface
and hold it in an upright position.
TIP
...
Checking the rear brake disc
1. Remove:
Rear wheel
Refer to "REAR WHEEL" on page 4-12.
2. Check:
Brake disc
Damage/galling → Replace.
3. Measure:
Brake disc deflection
Out of specification → Correct the brake
disc
deflection or replace the brake disc.
Refer to "CHECKING THE FRONT BRAKE
DIS ...
Replacing the front brake pads
NOTE:
When replacing the brake pads, it is not necessary
to disconnect the brake hose or disassemble
the brake caliper.
1. Measure:
Brake pad wear limit "a"
Out of specification Replace
the brake
pads as a set.
2. Install:
Brake pad support
Brake pad spring
Brake pads ...