oil YAMAHA YZ250F 2007 Manuale duso (in Italian)

6 - 4
–+ELECIGNITION SYSTEM
EC626002
IGNITION COIL INSPECTION
1. Inspect:
•Primary coil resistance
Out of specification → Replace.
Tester (+) lead
→ Orange lead
1
Tester (–) lead
→ Black lead
2
Primary coil
resistanceTester selector
position
0.08 ~ 0.10
Ω at
20 °C (68 °F)Ω
× 1
2. Inspect:
•Secondary coil resistance
Out of specification → Replace.
3. Inspect:
•Sealed portion of ignition coil a
•Spark plug terminal pin b
•Threaded portion of spark plug c
Wear → Replace.
CDI MAGNETO INSPECTION
1. Inspect:
•Pickup coil resistance
Out of specification → Replace. Tester (+) lead
→ Orange lead
1
Tester (–) lead
→ Spark plug terminal
2
Secondary coil
resistanceTester selector
position
4.6 ~ 6.8 k
Ω at
20 °C (68 °F)k
Ω
× 1
Tester (+) lead
→ Red lead
1
Tester (–) lead
→ White lead
2
Pickup coil
resistanceTester selector
position
248 ~ 372
Ω at
20 °C (68 °F)Ω
× 100
W
RBr
GP
B
1 2

6 - 5
–+ELECIGNITION SYSTEM
2. Inspect:
•Charging coil 1 resistance
Out of specification → Replace.
3. Inspect:
•Charging coil 2 resistance
Out of specification → Replace. Tester (+) lead
→ Brown lead
1
Tester (–) lead
→ Green lead
2
Charging coil 1
resistanceTester selector
position
720 ~ 1,080
Ω
at 20 °C (68 °F)Ω
× 100
Tester (+) lead
→ Pink lead
1
Tester (–) lead
→ Black lead
2
Charging coil 2
resistanceTester selector
position
44 ~ 66
Ω at
20 °C (68 °F)Ω
× 10
W
RBr
GP
B
2 1
2
1
W
RBr
GP
B
NEUTRAL SWITCH INSPECTION
1. Inspect:
•Neutral switch conduct
No continuous while in neutral → Replace.
Continuous while in gear → Replace.
EC628000
CDI UNIT INSPECTION
Check all electrical components. If no fault is
found, replace the CDI unit. Then check the
electrical components again.Tester (+) lead
→ Sky blue lead
1
Tester (–) lead
→ Ground
2
Sb
1 Ground
2
Tester selec-
tor position
NEUTRAL
Ω
×
×× × 1
IN GEAR
–+ Ω×1
1
2
Sb

–+ELEC
6 - 6
THROTTLE POSITION SENSOR SYSTEM
THROTTLE POSITION SENSOR SYSTEM
INSPECTION STEPS
If the throttle position sensor will not operate, use the following inspection steps.
* marked: Refer to “IGNITION SYSTEM” section.
NOTE:
Use the following special tools in this inspection.
Pocket tester:
YU-3112-C/90890-03112
Check entire ignition
system for connection.Repair or replace.
Check throttle position
sensor.Throttle posi-
tion sensor coilReplace.
*Check CDI magneto. Charging coil Replace.
Check CDI unit.Throttle posi-
tion sensor
input voltageReplace.
OK
OK
OK
No good
No good
No good
No good

6 - 7
–+ELECTHROTTLE POSITION SENSOR SYSTEM
HANDLING NOTE
CAUTION:
Do not loosen the screws (throttle position
sensor)
1 except when changing the throt-
tle position sensor due to failure because it
will cause a drop in engine performance.
1
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
•Couplers and leads connection
Rust/dust/looseness/short-circuit →
Repair or replace.
THROTTLE POSITION SENSOR COIL
INSPECTION
1. Inspect:
•Throttle position sensor coil resistance
Out of specification → Replace.
Tester (+) lead
→ Blue lead
1
Tester (–) lead
→ Black lead
2
Throttle posi-
tion sensor coil
resistanceTester selector
position
4 ~ 6 kΩ at
20 °C (68 °F)kΩ × 1
2. Loosen:
•Throttle stop screw 1
NOTE:
Turn out the throttle stop screw until the throt-
tle shaft is in the full close position.

6 - 8
–+ELECTHROTTLE POSITION SENSOR SYSTEM
3. Inspect:
•Throttle position sensor coil variable
resistance
Check that the resistance in increased as
the throttle grip is moved from the full
close position to the full open position.
Out of specification → Replace.
Tester (+) lead
→ Yellow lead
1
Tester (–) lead
→ Black lead
2
Throttle position sen-
sor coil variable
resistanceTester
selector
position
Full
closedFull
opened
k
Ω
× 1
Zero ~ 3 k
Ω
at 20 °C
(68°F)4 ~ 6 k
Ω at
20 °C
(68°F)
THROTTLE POSITION SENSOR
REPLACEMENT AND ADJUSTMENT
1. Remove:
•Throttle position sensor coupler
•Carburetor
2. Remove:
•Screw (throttle position sensor) 1
•Throttle position sensor 2
NOTE:
Loosen the screws (throttle position sensor)
using the T25 bit.
3. Replace:
•Throttle position sensor
2
1
4. Install:
•Throttle position sensor 1
•Screw (throttle position sensor) 2
NOTE:
•Align the slot a in the throttle position sensor
with the projection b on the carburetor.
•Temporarily tighten the screws (throttle posi-
tion sensor).
b
a
2 1

7 - 13
TUNSETTING
Front fork setting
The front fork setting should be made depend-
ing on the rider’s feeling of an actual run and
the circuit conditions.
The front fork setting includes the following
three factors:
1. Setting of air spring characteristics
•Change the fork oil amount.
2. Setting of spring preload
•Change the spring.
3. Setting of damping force
•Change the compression damping.
•Change the rebound damping.
The spring acts on the load and the
damping force acts on the cushion travel
speed.
Change in amount and characteristics of
fork oil
Damping characteristic near the final stroke
can be changed by changing the fork oil
amount.
CAUTION:
Adjust the oil amount in 5 cm
3 (0.2 Imp oz,
0.2 US oz) increments or decrements. Too
small oil amount causes the front fork to
produce a noise at full rebound or the rider
to feel some pressure on his hands or
body. Alternatively, too large oil amount
will cause the air spring characteristics to
have a tendency to be stiffer with the con-
sequent deteriorated performance and
characteristics. Therefore, adjust the front
fork within the specified range.
ÈAir spring characteristics in relation to oil amount
change
ÉLoad
ÊStroke
1Max. oil amount
2Standard oil amount
3Min. oil amount
Standard oil amount:
340 cm3
(12.0 Imp oz, 11.5 US oz)
Extent of adjustment:
300 ~ 380 cm
3
(10.6 ~ 13.4 Imp oz,
10.1 ~ 12.8 US oz)

7 - 20
TUNSETTING
EC72H002
Suspension setting
•Front fork
NOTE:
•If any of the following symptoms is experienced with the standard position as the base, make
resetting by reference to the adjustment procedure given in the same chart.
•Before any change, set the rear shock absorber sunken length to the standard figure 90 ~ 100 mm
(3.5 ~ 3.9 in).
SymptomSection
Check Adjust
JumpLarge
gapMedium
gapSmall
gap
Stiff over entire rangeCompression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Oil amount Decrease oil amount by about 5 ~ 10 cm
3 (0.2 ~
0.4 Imp oz, 0.2 ~ 0.3 US oz).
Spring Replace with soft spring.
Unsmooth movement
over entire rangeOuter tube Check for any bends, dents, and other noticeable
scars, etc. If any, replace affected parts.
Inner tube
Slide metal Replace with a new one for extended use.
Piston metal Replace with a new one for extended use.
Under bracket tightening
torqueRetighten to specified torque.
Poor initial
movementRebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Oil seal Apply grease in oil seal wall.
Soft over entire
range, bottoming outCompression damping Turn adjuster clockwise (about 2 clicks) to increase
damping.
Oil amount Increase oil amount by about 5 ~ 10 cm
3 (0.2 ~ 0.4
Imp oz, 0.2 ~ 0.3 US oz).
Spring Replace with stiff spring.
Stiff toward stroke
endOil amountDecrease oil amount by about 5 cm
3 (0.2 Imp oz,
0.2 US oz).
Soft toward stroke
end, bottoming outOil amountIncrease oil amount by about 5 cm
3 (0.2 Imp oz,
0.2 US oz).
Stiff initial movement Compression dampingTurn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low front, tending to
lower front postureCompression damping Turn adjuster clockwise (about 2 clicks) to increase
damping.
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Balance with rear end Set sunken length for 95 ~ 100 mm (3.7 ~ 3.9 in)
when one passenger is astride seat (lower rear pos-
ture).
Oil amount Increase oil amount by about 5 cm
3 (0.2 Imp oz,
0.2 US oz).
“Obtrusive” front,
tending to upper front
postureCompression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Balance with rear end Set sunken length for 90 ~ 95 mm (3.5 ~ 3.7 in)
when one passenger is astride seat (upper rear pos-
ture).
Spring Replace with soft spring.
Oil amount Decrease oil amount by about 5 ~ 10 cm
3 (0.2 ~ 0.4
Imp oz, 0.2 ~ 0.3 US oz).