2006 YAMAHA YZ125LC check oil

4-28
ENGCYLINDER HEAD, CYLINDER AND PISTON
3. Install:
9Nut (cylinder) 1
NOTE:
Tighten the nuts in stage, using a crisscross pat-
tern.
4. Install:
9Collar 1
9Push rod 2
9Plain washer 3
9Bolt (push rod) 4
NOTE:
9Set the collar 5included in owner's tool kit to
install the bolt (push rod).
9Do not forget to remove the collar.
EC4753A2
Cylinder head and cylinder
1. Apply:
9Engine oil
To piston 1, piston ring 2and cylinder
surface.
2. Install:
9Cylinder 1
cC
Make sure the piston ring is properly posi-
tioned. Install the cylinder with one hand
while compressing the piston ring with the
other hand.
NOTE:
After installing, check the smooth movement of
the piston.
30 Nm (3.0 m•kg, 22 ft•lb)
5 Nm (0.5 m•kg, 3.6 ft•lb)
1C3-9-31-4B 4/28/05 2:38 PM Page 22

8. Install:
9Segment 1
9Bolt (segment) 2
NOTE:
9When installing the segment onto the shift cam
3, align the punch mark awith the dowel pin
b.
9Turn the segment clockwise until it stops and
tighten the bolt.
cC
If the segment gets an impact, it may be
damaged. Take care not to give an impact
to the segment when tightening the bolt.
9. Remove:
9Sealant
Forced out on the cylinder mating surface.
10. Apply:
9Engine oil
To the crank pin, bearing, oil delivery hole
and connecting rod big end washer.
11. Check:
9Crankshaft and transmission operation
Unsmooth operation Repair.
NOTE:
If the crankshaft will not turn smoothly, make an
adjustment by gently tapping its right end with a
soft hammer.
4-68
ENGCRANKCASE AND CRANKSHAFT
30 Nm (3.0 m•kg, 22 ft•lb)
1C3-9-31-4D 4/28/05 2:41 PM Page 26

4-71
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H4801
Shift fork, shift cam and segment
1. Inspect:
9Shift fork 1
Wear/Damage/Scratches Replace.
2. Inspect:
9Shift cam 1
9Segment 2
9Guide bar 3
Bend/Wear/Damage Replace.
3. Check:
9Shift fork movement
On its guide bar.
Unsmooth operation Replace shift fork
and/or guide bar.
NOTE:
For a malfunctioning shift fork, replace not only
the shift fork itself but the two gears each adja-
cent to the shift fork.
EC4H5000
ASSEMBLY AND INSTALLATION
EC4H5213
Transmission
1. Install:
96th pinion gear (21T) 1
93rd/4th pinion gear (17T/17T) 2
95th pinion gear (20T) 3
92nd pinion gear (15T) 4
To main axle 5.
NOTE:
Apply the molybdenum disulfide oil on the inner
and end surface of the idler gear and on the
inner surface of the sliding gear, then install.
1C3-9-31-4D 4/28/05 2:41 PM Page 32

5-34
CHASFRONT FORK
5. Measure:
9Oil level (left and right) a
Out of specification  Adjust.
Standard oil level:
145~148 mm (5.71~5.83 in)
From top of fully stretched
damper assembly.
6. Tighten:
9Locknut 1
NOTE:
Fully finger tighten the locknut onto the
damper assembly.
7. Loosen:
9Compression damping adjuster 1
NOTE:
9Loosen the compression damping adjuster fin-
ger tight.
9Record the set position of the adjuster (the
amount of turning out the fully turned in posi-
tion).
8. Install:
9Base valve 1
To damper assembly 2.
NOTE:
First bring the damper rod pressure to a maxi-
mum. Then install the base valve while releas-
ing the damper rod pressure.
9. Check that the damper assembly is fully
stretched.
Not fully stretched  Repeat the steps 2 to 8.
1C3-9-31-5B 9/12/05 3:57 PM Page 18

10. Tighten:
9Base valve 1
NOTE:
Hold the damper assembly with the cap bolt
ring wrench
2and use the cap bolt wrench 3
to tighten the base valve with specified torque.
11. After filling, pump the damper assembly 1
slowly up and down more than 10 times to
distribute the fork oil.
5-35
CHASFRONT FORK
12. While protecting the damper assembly 1
with a rag and compressing fully, allow
excessive oil to overflow on the base valve
side.
cC
Take care not to damage the damper
assembly.
13. Allow the overflowing oil to escape at the
hole ain the damper assembly.
14. Check:
9Damper assembly smooth movement
Tightness/Binding/Rough spots  Repeat
the steps 2 to 13.
29 Nm (2.9 m•kg, 21 ft•lb)
Cap bolt wrench:
YM-01500/90890-01500
Cap bolt ring wrench:
YM-01501/90890-01501
1C3-9-31-5B 5/11/05 1:30 PM Page 20

6-2
ELECIGNITION SYSTEM
EC620000
IGNITION SYSTEM
EC621003
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
*Clean or replace
spark plug.
Primary coil
Secondary coil
Repair or replace.
Spark
Check entire ignition
system for connection.
Spark gap test
No good
No good
No good
No good
No good
No good No Spark
Check “ENGINE STOP”
button.
Pick-up coil
Source coil
Check ignition coil.
Check CDI magneto.
Replace CDI unit.
Replace.
Replace.
Replace.
Replace.
Replace.
*marked: Only when the ignition checker is used.
NOTE:
9Remove the following parts before inspection.
1) Seat
2) Fuel tank
9Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket tester:
YU-3112-C/90890-03112
OK
OK
OK
OKReplace.
Check spark plug cap.No good
OK
1C3-9-31-6 4/21/05 3:31 PM Page 4

6-6
ELECIGNITION SYSTEM
3. Inspect:
9Source coil 2 resistance
Out of specification 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 (+) leadGreen/Blue lead 1
Tester (–) lead
Black lead 2
Source coil 2 Tester selector
resistance position
44~66Ωat
Ω× 10
20°C (68°F)
1C3-9-31-6 4/21/05 3:32 PM Page 14

7-1
TUNSETTING
EC700000
TUNINGEC710000
ENGINEEC711001
Carburetor setting
9The role of fuel is to cool the engine, and in the
case of a 2-stroke engine, to lubricate the
engine in addition to power generation.
Accordingly, if a mixture of air and fuel is too
lean, abnormal combustion will occur, and
engine seizure may result. If the mixture is too
rich, spark plugs will get wet with oil, thus mak-
ing it impossible to bring the engine into full play
or if the worst comes to the worst, the engine
may stall.
9The richness of the air-fuel mixture required for
the engine will vary with atmospheric conditions
of the day and therefore, the settings of the car-
buretor must be properly suited to the atmos-
pheric conditions (air pressure, humidity and
temperature).
9Finally, the rider himself must make a test-run
and check his machine for conditions (pick-up of
engine speed, road surface conditions) and for
the discoloration of the spark plug(s). After tak-
ing these into consideration, he must select the
best possible carburetor settings.
It is advisable to make a note of settings,
atmospheric conditions, road surface condition,
lap-time, etc. so that the memorandum can be
used as a reference useful for future.
EC712000
Atmospheric conditions and carburetor
setting
The reason for the above tendency is that the
richness or leanness of a fuel mixture depends
on the density of the air (i.e. the concentration of
oxygen in it).
Air
Air temp. Humidity pressure Mixture Setting
(altitude)
High HighLow
Richer Leaner
(high)
Low LowHigh
Leaner Richer
(low)
1C3-9-31-7A 5/13/05 5:53 PM Page 2