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...

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...

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...

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...

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...

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...