Yamaha MBK XMAX 2014, Service Manual

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FEATURES
1-3
EAS37P1141
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 a certain level. 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, coolant temperature sensor, lean angle sensor, crankshaft position sensor, in-
take air pressure sensor, intake air temperature sensor, speed sensor (for YP125R), front wheel sensor
(for YP125RA) and O
2
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.
1
3
4
14
15
17
18
6
B
5
12
2
7
9
8
10
11
C
13
16
A
1. Fuel pump
2. Pressure regulator
3. Fuel injector
4. Ignition coil
5. Coolant temperature sensor
6. ECU (engine control unit)
7. ISC (idle speed control) unit
8. Throttle position sensor
9. Lean angle sensor
10. Speed sensor (for YP125R)
11. Front wheel sensor (for YP125RA)
12. O
2
sensor
13. Catalytic converter
14. Crankshaft position sensor
15. Intake air pressure sensor
16. Throttle body
17. Intake air temperature sensor
18. Air filter case
A. Fuel system
B. Air system
C. Control system