Yamaha Fz1n Service Manual

							
THROTTLE BODIES
7-5
For installation, reverse the removal 
procedure.
Removing the throttle bodies
Order Job/Parts to remove Q’ty Remarks 
						

							
THROTTLE BODIES
7-6
Removing the injectors
Order Job/Parts to remove Q’ty Remarks1 Throttle position sensor coupler 1 Disconnect.
2 Sub-throttle position sensor coupler 1 Disconnect.
3 Sub-throttle motor assembly coupler 1 Disconnect.
4 Intake air pressure s ensor coupler 1 Disconnect.
5 Cylinder #1-injector coupler 1 Disconnect.
6 Cylinder #2-injector coupler 1 Disconnect.
7 Cylinder #3-injector coupler 1 Disconnect.
8 Cylinder #4-injector coupler 1 Disconnect.
9 Sub-wire harness 1
10 Negative pressure hose 1 Disconnect.
11 Intake air pressure sensor 1
12 Fuel distributor 1
13 Injector 4
14 Spring 1
15 Thermo wax assembly 1
16 Idle adjust screw wire 1
17 Link cover 1 Loosen.
18 Cotter pin 2 
						

							
THROTTLE BODIES
7-7
19 Washer 2
20 Link 1
21 Sub-throttle servo motor assembly 1
22 Throttle position sensor 1
23 Throttle body assembly 1For installation, reverse the removal 
procedure.
Removing the injectors
Order Job/Parts to remove Q’ty Remarks 
						

							
THROTTLE BODIES
7-8
EAS26980
CHECKING THE INJECTORS
1. Check: Injectors
Damage  → Replace.
EAS26990
CHECKING THE THROTTLE BODIES
1. Check:
 Throttle bodies
Cracks/damage  → Replace the throttle 
bodies as a set.
2. Check:
 Fuel passagesObstructions  → Clean.
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a. Wash the throttle bodies in a petroleum- 
based solvent.
Do not use any causti c carburetor cleaning 
solution.
b. Blow out all of the passages with com- pressed air.
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ET2D1033
CHECKING THE FUEL PRESSURE
1. Check:
 Fuel pressure
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a. Remove the rider and passenger seat. Refer to GENERAL CHASSIS on page 4-
1.
b. Disconnect the fuel hose (fuel tank to pri- mary injector fuel rail) “1” from the primary 
injector fuel rail.
WARNING
EW2C01008
Cover fuel hose connections with a cloth 
when disconnecting them. Residual pres-
sure in the fuel lines could cause fuel to 
spurt out when removing the hoses. c. Connect the pressure gauge “2” and 
adapter “3” to the fuel hose (fuel tank to pri-
mary injector fuel rail).
d. Start the engine.
e. Measure the fuel pressure. Faulty  → Replace the fuel pump.
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EAS27020
ADJUSTING THE THROTTLE POSITION 
SENSOR
NOTE:
Before adjusting the throttle position sensor, 
the engine idling speed should be properly 
adjusted.
Vacuum/pressure pump gauge 
set
90890-06756
Pressure gauge 90890-03153
YU-03153
Fuel pressure adapter 90890-03176
YM-03176
Fuel pressure324 kPa (46.1 psi) (3.24 kg/
cm²) 
						

							
THROTTLE BODIES
7-9
1. Check: Throttle position sensor
Refer to CHECKING THE THROTTLE 
POSITION SENSOR on page 8-109.
2. Adjust:
 Throttle position sensor angle
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a. Connect the throttle position sensor cou- pler to the wire harness.
b. Connect the digital circuit tester to the  throttle position sensor.
c. Measure the throttle position sensor volt- age.
d. Adjust the throttle position sensor angle so  the measured voltage is within the speci-
fied range.
e. After adjusting the throttle position sensor  angle, tighten the throttle position sensor 
screws.
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ET2D1024
ADJUSTING THE SUB-THROTTLE POSI-
TION SENSOR
1. Check:
 Sub-throttle position sensorRefer to CHECKING THE SUB-THROT-
TLE POSITION SENSOR on page 8-110.
2. Adjust:  Sub-throttle position sensor full open angle
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a. Turn the nut “1” of the worm shaft of the  sub-throttle counterclockwise until it con-
tacts with the full open stopper.
b. When the dimension of “a” sections of the  throttle bodies #3 and #4 is measured with 
a micrometer caliper, adjust with the 
adjuster “2” of the output shaft section of 
the sub-throttle servo motor so that the 
dimension is in a range from 24.2 to 24.6 
mm (0.95 to 0.97 in.)
c. After adjusting the dimension of “a” sec- tions of the throttle bodies #3 and #4, mea-
sure the dimension of “a” sections of #1 
and #2.
d. If the dimension of “a” sections of the throt- tle bodies #1 and #2 is different from the 
dimension of “a” sections of the throttle 
bodies #3 and #4, adjust it to the same 
dimension as the measurement value 
adjusted for the throttle bodies #3 and #4, 
using the tuning screw “3” located between 
the throttle bodies #2 and #3.
 Positive tester probe
yellow terminal “1”
 Negative tester probe black/blue terminal “2”
Digital circuit tester
90890-03174
Throttle position sensor voltage0.63–0.73 V
Sub-throttle dimension “a”
24.2–24.6 mm (0.95–0.97 in) 
						

							
THROTTLE BODIES
7-10
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3. Adjust: Primary opening
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a. After performing the full open angle of the  sub-throttle position sensor, turn the nut of 
the worm shaft clockwise, measure the 
dimension of “b” section with a micrometer 
caliper or other device and adjust so that 
the dimension is in a range from 8.1 to 8.5 
mm (0.32 to 0.33 in).
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4. Adjust: Sub-throttle position sensor voltage
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a. Connect the sub-throttle position sensor  coupler to the wire harness.
b. Connect the digital circuit tester to the sub- throttle position sensor.
c. Move the sub-throttle position sensor to  adjust to be in the specified range.
d. After adjusting the sub-throttle position  sensor voltage, tighten the sub-throttle 
position sensor screws.
NOTE:
 After setting up the sub-throttle position sen-
sor, check that the sub-throttle position sen-
sor output voltage is 0.4 V or more with the 
nut of worm shaft turned to the full close side 
until it stops.
 When the sub-throttle position sensor output 
voltage is 0.4 V or more, check that the sub-
throttle position sensor output voltage is 4.6 
V or less with the nut of worm shaft turned to 
the full open side until it stops.
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5. Connect Sub-throttle motor assembly coupler
EAS2D1011
CHECKING THE SUB-THROTTLE SERVO 
MOTOR
1. Check: Sub-throttle servo motor operation
A. Front side
B. Rear side
Sub-throttle dimension “b”8.1–8.5 mm (0.32–0.33 in)
A. Front side
B. Rear side
 Positive tester probeGreen/Yellow terminal “1”
 Negative tester probe Black/Blue terminal “2”
Digital circuit tester90890-03174
Sub-throttle position sensor 
voltage0.97–1.07 V 
						

							
THROTTLE BODIES
7-11
Out of specification → Replace.
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a. Check whether or not the sub-throttle valve 
is seized.
1 Turn the nut of worm shaft of the sub-throt-
tle servo motor by hand to check that the 
sub-throttle valve is moved smoothly by 
hand.
2 If it is not moved smoothly, disconnect the  link between the sub-throttle servo motor 
and sub-throttle valve, and then check 
whether or not the sub-throttle valve is 
moved smoothly by hand.
Refer to THROTTLE BODIES on page 7-
4.
3 When the sub-throttle valve is not moved  smoothly, repair or replace it since the 
cause is the seizure of sub-throttle valve 
body itself.
When it moved smoothly at Step (1) and 
(2), replace the sub-throttle servo motor.
b. Perform the self-diagnosis mode and check  the operation of sub-throttle valve by visual 
inspection (Code No: 56).
The operation should be carried out as 5-
second drive in the full open direction, 2-
second stop and 5-second drive in the full 
close direction.
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EAT2D1004
CHECKING THE THERMO WAX
1. Check:
 Thermo wax  “1”Damage  → Replace the thermo wax 
assembly.
ET2D1025
ADJUSTING THE THERMO WAX
1. Adjust:
 Thermo wax the end face distance “a”
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a. Before adjusting the distance, push the rod  “b” in order to be fitted in several times by 
hand.
b. Measure the outside air temperature, and  adjust the distance “a” by turning the 
adjusting screw “2”. Refer to the thermo 
wax tolerance table based on the mea-
sured outside air temperature for correct 
adjustment.
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NOTE:
 Setup tolerance of the longitudinal axis 
should be ± 0.2 mm ( ± 0.008 in).
 After adjusting the thermo wax, check that 
the first idling is released at the coolant tem-
perature around 60 °C (140 °F) by idling.
 If the first idling is not released around 60 °C 
(140 °F), make sure to set it again. (When the 
coolant temperature is  low, adjust the dis-
tance between the end faces longer or adjust  
						

							
THROTTLE BODIES
7-12
it shorter when the coolant temperature is 
high.)
 In case of turning the adjusting bolt two-third  turn, the temperature varies about 10 °C 
(50 °F). 
						

							
AIR INDUCTION SYSTEM
7-13
EAS27040
AIR INDUCTION SYSTEM
Removing the air cut-off valve assembly and hoses
Order Job/Parts to remove Q’ty Remarks1 Air cut-off valve coupler 1 Disconnect.
2 Air cut-off valve hose 1 1 Disconnect.
3 Air cut-off valve hose 2 1 Disconnect.
4 Air cut-off valve hose 3 1 Disconnect.
5 Air cut-off valve 1
6 Reed valve cap 2
7 Reed valve assembly 2
8Plate 4 For assembly, reverse the removal 
procedure. 
						

							
AIR INDUCTION SYSTEM
7-14
EAS27060
CHECKING THE AIR INDUCTION SYSTEM
Air injection
The air induction system burns unburned 
exhaust gases by injecting fresh air (second-
ary air) into the exhaust port, reducing the 
emission of hydrocarbons. When there is neg-
ative pressure at the exhaust port, the reed 
valve opens, allowing secondary air to flow into 
the exhaust port. The required temperature for 
burning the unburned exhaust gases is 
approximately 600 to 700°C.
Air cut-off valve
The air cut-off valve is controlled by the signals 
from the ECU in accordance with the combus-
tion conditions. Ordinarily, the air cut-off valve 
opens to allow the air to flow during idle and 
closes to cut-off the flow when the vehicle is 
being driven. However, if the coolant tempera-
ture is below the specified value, the air cut-off 
valve remains open and allows the air to flow 
into the exhaust pipe until the temperature 
becomes higher than the specified value.
1. Check:Hoses
Loose connections  → Connect properly.
Cracks/damage  → Replace.
Pipes
Cracks/damage  → Replace.
2. Check:  Reed valve “1”
 Reed valve stopper
 Reed valve seatCracks/damage  → Replace the reed valve.
3. Measure:  Reed valve bending limit “a”
A. From the air cleaner
B. To the cylinder head