2001 YAMAHA YZ125LC check oil

4-27
ENGCYLINDER HEAD, CYLINDER AND PISTON
EC475233
Piston ring and piston
1. Install:
9Piston ring 1
NOTE:
9Take care not to scratch the piston or damage
the piston ring.
9Align the piston ring gap with the pin 2.
9After installing the piston ring, check the
smooth movement of it.
2. Install:
9Gasket (cylinder) 1
9Small end bearing 2
9Dowel pin 3
NOTE:
9Apply the engine oil onto the bearing (crank-
shaft and connecting rod) and connecting rod
big end washers.
9Install the gasket with the seal print side toward
the crankcase.
3. Install:
9Piston 1
9Piston pin 2
9Piston pin clip 3
NOTE:
9The arrow aon the piston dome must point to
exhaust side.
9Before installing the piston pin clip, cover the
crankcase with a clean rag to prevent the pis-
ton pin clip from falling into the crankcase cavi-
ty.
cC
Do not allow the clip open ends to meet the
piston pin slot b b
.
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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.
EC4753A1
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)
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4-68
ENGCRANKCASE AND CRANKSHAFT
6. Install:
9Holder 1
9Bolt (holder) 2
7. 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.
8. Remove:
9Sealant
Forced out on the cylinder mating surface.
9. Apply:
9Engine oil
To the crank pin, bearing, oil delivery hole
and connecting rod big end washer.
10. Check:
9Crankshaft and transmission operation
Unsmooth operation ÕRepair.
30 Nm (3.0 m•kg, 22 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
5MV-9-30-4D 6/19/00 1:39 PM Page 24

4-71
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H4801
Shift fork, shift cam and segment
1. Inspect:
9Shift fork 1
Wear/Damage/Scratches ÕReplace.
2. Inspect:
9Shift cam 1
9Segment 2
9Guide bar 3
Bend/Wear/Damage ÕReplace.
3. Check:
9Shift fork movement
On its guide bar.
Unsmooth operation ÕReplace 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
EC4H5202
Transmission
1. Install:
95th pinion gear (23T) 1
93rd/4th pinion gear (17T/21T) 2
96th pinion gear (24T) 3
92nd pinion gear (15T) 4
To main axle 5.
NOTE:
9Apply the molybdenum disulfide oil on the 5th
and 6th pinion gears inner circumference.
9Apply the transmission oil on the 2nd and
3rd/4th pinion gears inner circumference.
5MV-9-30-4D 6/19/00 1:39 PM Page 30

4-73
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H5331
Shift cam and shift fork
1. Install:
9Shift fork 1 (L) 1
9Shift fork 2 2
9Shift fork 3 (R) 3
NOTE:
9Mesh the shift fork #1 (L) with the 6th wheel
gear 4and #3 (R) with the 5th wheel gear 6
on the drive axle.
9Mesh the shift fork #2 with the 3rd/4th pinion
gear 5on the main axle.
2. Install:
9Shift cam 1
NOTE:
Apply the transmission oil on the shift cam.
3. Install:
9Guide bar (short) 1
9Guide bar (long) 2
NOTE:
9Apply the transmission oil on the guide bars.
9Be sure the long bar is inserted into the shift
forks #1 and #3 and the short one into #2.
4. Check:
9Shifter operation
9Transmission operation
Unsmooth operation ÕRepair.
5MV-9-30-4D 6/19/00 1:39 PM Page 34

5-35
CHASFRONT FORK
13. Check:
9Inner tube smooth movement
Tightness/Binding/Rough spots ÕRepeat the
steps 2 to 12.
14. Compress the front fork fully.
15. Fill:
9Front fork oil
Until outer tube top surface with recom-
mended fork oil 1.
cC
9Be sure to use recommended fork oil. If
other oils are used, they may have an ex-
cessively adverse effect on the front fork
performance.
9Never allow foreign materials to enter the
front fork.
16. After filling, pump the damper rod 1slowly
up and down more than 10 times to distrib-
ute the fork oil.
17. Fill:
9Front fork oil
Until outer tube top surface with recom-
mended fork oil once more.
18. After filling, pump the outer tube 1slowly
up and down (about 200 mm (7.9 in) stroke)
to distribute the fork oil once more.
NOTE:
Be careful not to excessive full stroke. A stroke
of 200 mm (7.9 in) or more will cause air to en-
ter. In this case, repeat the steps 15 to 18.
Recommended oil:
Suspension oil “01”
5MV-9-30-5B 6/19/00 1:29 PM Page 18

5-36
CHASFRONT FORK
19. Wait ten minutes until the air bubbles have
been removed from the front fork, and the
oil has dispense evenly in system before
setting recommended oil level.
NOTE:
Fill with the fork oil up to the top end of the outer
tube, or the fork oil will not spread over to every
part of the front forks, thus making it impossible
to obtain the correct level.
Be sure to fill with the fork oil up to the top of the
outer tube and bleed the front forks.
20. Measure:
9Oil level (left and right) a
Out of specification Õ Adjust.
NOTE:
Be sure to install the spring guide 2when
checking the oil level.
w
Never fail to make the oil level adjustment
between the maximum and minimum level
and always adjust each front fork to the
same setting. Uneven adjustment can
cause poor handling and loss of stability.
Standard oil level:
135 mm (5.31 in)
Extent of adjustment:
80~150 mm (3.15~5.91 in)
From top of outer tube with
inner tube and damper rod
1 1
fully compressed without spring.
5MV-9-30-5B 6/19/00 1:29 PM Page 20

6-2
ELECIGNITION SYSTEM
EC620000
IGNITION SYSTEM
EC621002
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
OK
5MV-9-30-6 6/19/00 1:25 PM Page 4