2001 YAMAHA YZ125LC stop start

2-5
SPECMAINTENANCE SPECIFICATIONS
Part to be tightened Thread size Q'tyT ightening torqueNm m•kg ft•lb
Spark plug M14 ´1.25 1 20 2.0 14
Cylinder head (nut) M 8 ´1.25 5 28 2.8 20
(stud) M 8 ´1.25 5 13 1.3 9.4
Cylinder (nut) M 8 ´1.25 4 30 3.0 22
(stud) M10 ´1.25 4 13 1.3 9.4
Power valve:
Cover M 5 ´0.8 4 4 0.4 2.9
Link lever M 4 ´0.7 1 4 0.4 2.9
Holder (power valve) M 5 ´0.8 4 8 0.8 5.8
Push rod M 5 ´0.8 1 5 0.5 3.6
Thrust plate M 5 ´0.8 1 4 0.4 2.9
Governor fork M 4 ´0.7 2 5 0.5 3.6
Housing M 5 ´0.8 4 5 0.5 3.6
Impeller M 8 ´1.25 1 14 1.4 10
Water pump housing cover M 6 ´1.0 4 10 1.0 7.2
Coolant drain bolt M 6 ´1.0 1 10 1.0 7.2
Radiator hose clamp M 6 ´1.0 8 1 0.1 0.7
Air filter element M 6 ´1.0 1 2 0.2 1.4
Carburetor joint M 6 ´1.0 4 10 1.0 7.2
Air filter case M 6 ´1.0 2 4 0.4 2.9
Air filter joint M 5 ´0.8 5 1 0.1 0.7
Read valve M 3 ´0.5 6 1 0.1 0.7
Crankcase M 6 ´1.0 12 14 1.4 10
Crankcase cover (right) M 6 ´1.0 8 10 1.0 7.2
Crankcase cover (left) M 6 ´1.0 5 5 0.5 3.6
Chain cover M 6 ´1.0 2 5 0.5 3.6
Bearing plate cover M 6 ´1.0 3 10 1.0 7.2
Holder M 6 ´1.0 1 10 1.0 7.2
Oil check bolt M 6 ´1.0 1 10 1.0 7.2
Oil drain bolt M12 ´1.5 1 20 2.0 14
Kick starter M 6 ´1.0 1 10 1.0 7.2
Cluch cover M 6 ´1.0 6 10 1.0 7.2
Primary drive gear M10 ´1.25 1 55 5.5 40
Clutch boss M16 ´1.0 1 80 8.0 58
Clutch spring M 6 ´1.0 5 10 1.0 7.2
Push lever axle M 6 ´1.0 1 7 0.7 5.1
Drive sprocket M16 ´1.0 1 60 6.0 43
Shift pedal M 6 ´1.0 1 10 1.0 7.2
Bearing plate cover (shift cam) M 6 ´1.0 2 10 1.0 7.2
Shift guide M 6 ´1.0 2 10 1.0 7.2
Stopper lever M 6 ´1.0 1 10 1.0 7.2
Segment M 8 ´1.25 1 30 3.0 22
5MV-9-30-2A 6/19/00 1:15 PM Page 6

3-15
INSP
ADJIDLE SPEED ADJUSTMENT/MUFFLER INSPECTION/
SILENCER FIBER REPLACEMENT
EC35M010
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it up.
2. Adjust:
9Idle speed
EC35P010
MUFFLER INSPECTION
1. Inspect:
9O-ring 1
Damage ÕReplace.
EC35R041
SILENCER FIBER REPLACEMENT
1. Remove:
9Seat
9Side cover (right)
9Bolt (silencer) 1
9Silencer 2
9Bolt (fiber) 3
Adjustment steps:
9Loosen the locknut 1.
9Turn the throttle stop screw 2until the
engine runs at the lowest possible speed.
9Tighten the locknut.
To increase idle speed ÕTurn the throttle
stop screw 2 2
in.
To decrease idle speed ÕTurn the throttle
stop screw 2 2
out.
5MV-9-30-3A 6/19/00 1:52 PM Page 38

4-8
ENGCARBURETOR AND REED VALVE
EC468000
CARBURETOR DISASSEMBLY
Extent of removal Order Part name Q’ty Remarks
CARBURETOR DISASSEMBLY
1Mixing chamber top 1
2Throttle valve 1 Refer to “REMOVAL POINTS”.
3Needle holder 1
4Jet needle 1
5Float chamber 1
6Needle jet cover 1
7Float pin 1
8Float 1
9Valve seat 1
0Main jet 1
qMain jet holder 1
wPilot jet 1
eStarter plunger 1
rThrottle stop screw 1
tPilot air screw 1
Extent of removal:1Carburetor disassembly
1
5MV-9-30-4A 6/19/00 1:47 PM Page 16

4-13
ENGCARBURETOR AND REED VALVE
2. Install:
9Reed valve assembly 1
9Reed valve spacer 2
NOTE:
Install the reed valve spacer with its wider con-
tact surface side ato the right.
3. Install:
9Carburetor joint 1
9Bolt (carburetor joint) 2
EC4652C2
Carburetor
1. Install:
9Throttle stop screw 1
9Locknut 2
9Pilot air screw 3
Pilot air screw:
1-1/4 turns out
*1-1/2 turns out
Note the following installation points:
9Screw in the pilot air screw until it is lightly
seated.
9Back out it by the specified number of turns.
* For EUROPE
10 Nm (1.0 m•kg, 7.2 ft•lb)
2. Install:
9Starter plunger 1
5MV-9-30-4A 6/19/00 1:47 PM Page 26

4-63
ENGCRANKCASE AND CRANKSHAFT
EC4N3000
REMOVAL POINTS
EC4N3100
Segment
1. Remove:
9Bolt (segment) 1
9Segment 2
NOTE:
Turn the segment counterclockwise until it stops
and loosen the bolt.
EC4N3211
Crankcase
1. Remove:
9Crankcase (right) 1
Use the crankcase separating tool 2and
crankcase separating bolt 3.
NOTE:
9Fully tighten the tool holding bolts, but make
sure the tool body is parallel with the case. If
necessary, one screw may be backed out
slightly to level tool body.
9As pressure is applied, alternately tap on the
front engine mounting boss and transmission
shafts.
cC
Use soft hammer to tap on the case half.
Tap only on reinforced portions of case. Do
not tap on gasket mating surface. Work
slowly and carefully. Make sure the case
halves separate evenly. If one end “hangs
up”, take pressure off the push screw, re-
align, and start over. If the cases do not
separate, check for a remaining case
screw or fitting. Do not force.
Crankcase separating tool:
YU-1135-A/90890-01135
Crankcase separating bolt:
YM-1305/90890-01305
5MV-9-30-4D 6/19/00 1:39 PM Page 14

6-3
ELECIGNITION SYSTEM
EC622001
SPARK GAP TEST
1. Disconnect the spark plug cap from spark
plug.
2. Connect the dynamic spark tester 1(igni-
tion checker 2) as shown.
9Spark plug cap 3
9Spark plug 4
AFor USA and CDN
BExcept for USA and CDN
3. Kick the kick starter.
4. Check the ignition spark gap.
5. Start engine, and increase spark gap until
misfire occurs. (for USA and CDN only)
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
9Couplers and leads connection
Rust/ Dust/ Looseness/Short-circuit Õ
Repair or replace.
EC625002
“ENGINE STOP” BUTTON INSPECTION
1. Inspect:
9“ENGINE STOP” button conduct
Not continuous while being pushed ÕReplace.
Continuous while being freed ÕReplace.
Minimum spark gap:
6.0 mm (0.24 in)
Tester (+) leadÕBlack/White lead 1
Tester (–) lead
ÕBlack lead 2
B/W B
12
PUSH IN
FREE
Tester selector
position
½´ 1
Œ
º
5MV-9-30-6 6/19/00 1:25 PM Page 8