2001 YAMAHA YZ250LC stop start

2-5
MAINTENANCE SPECIFICATIONSSPEC
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 6 25 2.5 18
(stud) M 8 ´1.25 6 13 1.3 9.4
Cylinder (nut) M10 ´1.25 4 35 3.5 25
(stud) M10 ´1.25 4 13 1.3 9.4
Power valve :
Holder M 5 ´0.8 2 6 0.6 4.3
Link rod M 5 ´0.8 2 6 0.6 4.3
Push rod M 5 ´0.8 1 5 0.5 3.6
Thrust plate M 5 ´0.8 1 6 0.6 4.3
Side holder M 5 ´0.8 4 4 0.4 2.9
Link lever M 4 ´0.7 1 4 0.4 2.9
Pulley M 4 ´0.7 2 4 0.4 2.9
Cover M 5 ´0.8 4 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 M 6 ´1.0 6 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 5 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
Reed valve M 3 ´0.5 4 1 0.1 0.7
Exhaust pipe M 6 ´1.0 2 12 1.2 8.7
Exhaust pipe stay (front) M 8 ´1.25 1 25 2.5 18
Exhaust pipe stay (rear) M 6 ´1.0 1 12 1.2 8.7
Silencer (front) M 6 ´1.0 1 12 1.2 8.7
Silencer (rear) M 6 ´1.0 1 7 0.7 5.1
Fiber (silencer) M 6 ´1.0 2 10 1.0 7.2
Crankcase M 6 ´1.0 11 14 1.4 10
Crankcase cover (left) M 6 ´1.0 5 8 0.8 5.8
Chain cover M 6 ´1.0 2 8 0.8 5.8
Crankcase cover (right) M 6 ´1.0 9 10 1.0 7.2
Bearing plate cover (drive axle left) M 6 ´1.0 2 10 1.0 7.2
Bearing plate cover (main axle right) M 6 ´1.0 2 10 1.0 7.2
Holder M 6 ´1.0 2 10 1.0 7.2
Oil drain bolt M12 ´1.5 1 20 2.0 14
Oil check bolt M 6 ´1.0 1 10 1.0 7.2
Kick starter M 8 ´1.25 1 30 3.0 22
Ratchet wheel stopper M 6 ´1.0 2 10 1.0 7.2
Clutch cover M 6 ´1.0 6 10 1.0 7.2
Primary drive gear M10 ´1.25 1 55 5.5 40
Clutch boss M20 ´1.0 1 75 7.5 54
5MW-9-30-2 7/3/00 2:20 PM Page 6

INSP
ADJ
3-15
IDLE SPEED ADJUSTMENT/MUFFLER INSPECTION/
SILENCER FIBER REPLACEMENT
EC35M001
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:
Turn the throttle stop screw 1until the
engine runs at the lowest possible speed.
To increase idle speed ÕTurn the throttle
stop screw 1 1
in.
To decrease idle speed ÕTurn the throttle
stop screw 1 1
out.
5MW-9-30-3A 7/3/00 2:53 PM Page 38

ENG
4-8
CARBURETOR 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
6Float pin 1
7Float 1
8Needle valve 1
9Main jet 1
0Pilot jet 1
qStarter plunger 1
wThrottle stop screw 1
ePilot air screw 1 Refer to “REMOVAL POINTS”.
rPower jet 1
tSolenoid valve 1
Extent of removal:1Carburetor disassembly
1
5MW-9-30-4A 7/3/00 5:02 PM Page 16

ENG
3. Install:
9Pilot air screw 1
9Throttle stop screw 2
*For EUROPE
4. Install:
9Starter plunger 1
4-14
CARBURETOR AND REED VALVE
Pilot air screw:
1 turn out
*1-3/4 turns out
(for reference only)
Note the following installation points:
9Turn in the pilot air screw until it is lightly
seated.
9Turn out the pilot air screw by the number of
turns recorded before removing.
5. Install:
9Pilot jet 1
9Main jet 2
6. Install:
9Needle valve 1
9Float 2
9Float pin 3
NOTE:
9After installing the needle valve to the float,
install them to the carburetor.
9Check the float for smooth movement.
7. Install:
9Float chamber 1
9Plate 2
9Screw (float chamber) 3
5MW-9-30-4A 7/3/00 5:24 PM Page 28

4-65
CRANKCASE AND CRANKSHAFTENG
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,
realign, and start over. If the cases do not
separate, check for a remaining case screw
or fitting. Do not force.
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.
Crankcase separating tool:
YU-1135-A/90890-01135
Crankcase separating bolt:
YM-1305/90890-01305
5MW-9-30-4C 7/4/00 9:25 AM Page 34

6-3
IGNITION SYSTEMELEC
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 selec-
tor position
½´ 1
Œ Œ
B
5MW-9-30-6 7/6/00 1:35 PM Page 8