2011 YAMAHA YZ125LC service

OWNER’S SERVICE MANUALMANUEL D’ATELIER DU PROPRIETAIRE
FAHRER- UND
WARTUNGSHANDBUCH
MANUALE DI SERVIZIO DEL PROPRIETARI
O

YZ125(
A )
/A1
1C3-28199-36
PRINTED IN JAPAN
2010.6—0.6
× 1
!(E, F, G, H)

YAMAHA MOTOR CO., LTD.
2500 SHINGAI IWATA SHIZUOKA JAPAN

PRINTED ON RECYCLED PAPER
2011

YZ125 (
A )
/A1
2011
qRead this manual carefully before operating this vehicle.
qIl convient de lire attentivement ce manuel avant la première utilisation du véhicule.
qBitte lesen Sie diese Bedienungsanleitung sorgfältig durch, bevor Sie das Fahrzeug in Betrieb nehmen.
qLeggere attentamente questo manuale prima di utilizzare questo veicolo.

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YZ125 (A)/A1
OWNER'S SERVICE MANUAL
©2010 by Yamaha Motor Co., Ltd. 1st Edition, June 2010
All rights reserved.Any reprinting or
unauthorized use wi thout the written
permission of Yamaha Motor Co., Ltd. is expressly prohibited.Printed in Japan

HOW TO READ DESCRIPTIONS
To help identify parts and clarify pro-
cedure steps, there are exploded dia-
grams at the start of each removal
and disassembly section.
1. An easy-to-see exploded diagram
"1" is provided for removal and
disassembly jobs.
2. Numbers "2" are given in the or-der of the jobs in the exploded di-
agram. A number that is enclosed
by a circle indicates a disassem-
bly step.
3. An explanation of jobs and notes
is presented in an easy-to-read
way by the use of symbol marks
"3". The meanings of the symbol
marks are given on the next page.4. A job instruction chart "4" accom-
panies the exploded diagram,
providing the order of jobs, names
of parts, notes in jobs, etc.
5. For jobs requiring more informa-
tion, the step-by-step format sup-
plements "5" are given in addition
to the exploded diagram and job
instruction chart.
ILLUSTRATED SYMBOLS (Refer to
the illustration)Illustrated symbols "1" to "7" are used
to identify the specifications appear-
ing in the text.
1. With engine mounted
2. Filling fluid
3. Lubricant
4. Special tool
5. Tightening
6. Specified value, Service limit
7. Resistance (Ω), Voltage (V),
Electric current (A)
Illustrated symbols "8" to "14" in the
exploded diagrams indicate grade of
lubricant and location of lubrication
point.
8. Apply engine mixing oil
9. Apply transmission oil
10. Apply molybdenum disulfide oil
11. Apply brake fluid
12. Apply lightweight lithium-soap
base grease
13. Apply molybdenum disulfide
grease
14. Apply silicone greaseIllustrated symbols "15" to "16" in the
exploded diagrams indicate where to
apply a locking agent and where to in-
stall new parts.
15. Apply locking agent (LOC-
TITE
®)
16. Use new one
1
23
45

1-4
LOCATION OF IMPORTANT LABELS
Familiarize yourself with the following pictograms and read the explanatory text.
Read Owner's service manual.
This unit contains high-pressure nitrogen gas. Mishandling can cause explosion. Do not incinerate,
puncture or open.
Turn off the main switch after riding to avoid draining the battery.
Use unleaded gasoline only.
Measure tire pressure when tires are cold.
Adjust tire pressure.
Improper tire pressure can cause loss of control.
Loss of control can result in severe injury or death.

2-1
GENERAL SPECIFICATIONS
SPECIFICATIONS
GENERAL SPECIFICATIONS
Model name: YZ125A1 (USA, CDN)YZ125 (EUROPE, ZA)
YZ125A (AUS, NZ)
Model code number: 1C3S (USA, CDN) 1C3T (EUROPE)
1C3V (AUS, NZ, ZA)
Dimensions: USA, AUS, NZ, ZA EUROPE, CDN Overall length 2,135 mm (84. 1 in) 2,139 mm (84.2 in)
Overall width 827 mm (32.6 in) ←
Overall height 1,315 mm (51.8 in) 1,318 mm (51.9 in)
Seat height 997 mm (39. 3in) 998 mm (39.3 in)
Wheelbase 1,443 mm (56.8 in) ←
Minimum ground clearance 386 mm (15.2 in) 388 mm (15.3 in)
Weight: With oil and fuel 94 kg (207 lb)
Engine: Engine type Liquid cooled 2-stroke, gasoline
Cylinder arrangement Single cylinder, forward inclined
Displacement 124 cm
3 (4.36 Imp oz, 4.19 US oz)
Bore × stroke 54 × 54.5 mm (2.126 × 2.146 in)
Compression ratio 8.6–10.7 : 1
Starting system Kick starter
Lubrication system: Premix (30 : 1)(Yamalube 2-R)
Oil type or grade (2-stroke): Transmission oil Recommended brand: YAMALUBE SAE10W-40
API service SG type or higher
JASO standard MA
Periodic oil change 0.66 L (0.58 Imp qt, 0.69 US qt)
Total amount 0.70 L (0.62 Imp qt, 0.74 US qt)
Coolant capacity (including all routes): 0.9 L (0.79 Imp qt, 0.95 US qt)
Air filter: Wet type element
Fuel: Type Premium unleaded gasoline on ly with a research octane
number of 95 or higher.
Tank capacity 8.0 L (1.76 Imp gal, 2.11 US gal)
Carburetor: Type/Manufacturer TMX χ38SS/MIKUNI
Spark plug: Type/Manufacturer BR9EVX/NGK (resistance type)
Gap 0.6–0.7 mm (0.024–0.028 in)
Clutch type: Wet, multiple-disc
2

3-1
MAINTENANCE INTERVALS
REGULAR INSPECTION AND ADJUSTMENTS
MAINTENANCE INTERVALS
• The following schedule is intended as a general guide to maintenance and lubrication. Bear in mind that such factors as
weather, terrain, geographical location, and individual usage will alter the required maintenance and lubrication intervals.
If you are a doubt as to what intervals to follow in maintaining and lubricating your machine, consult your Yamaha dealer.
• Periodic inspection is essential in making full use of the machine performance. The service life of the parts varies sub-
stantially according to the environment in which the machine runs (e.g., rain, dirt, etc.). Therefore, earlier inspection is
required by reference to the list below.
ItemAfter
break-in
Every
race
(about
2.5
hours)Every
third
(about
7.5
hours)Every
fifth
(about
12.5
hours)
As re-
quiredRemarks
PISTON
Inspect and clean●●Inspect crack.
Replace●●Inspect carbon deposits and
eliminate them.
PISTON RING
Inspect●●Check ring end gap.
Replace●●
PISTON PIN, SMALL END
BEARING
Inspect●
Replace●
CYLINDER HEAD Inspect carbon deposits and
eliminate them.
Inspect and clean●●Check gasket.
Retighten●●
CYLINDER
Inspect and clean●●Inspect score marks.
Replace●Inspect wear.
YPVS
Inspect and clean●●Inspect carbon deposits and
eliminate them.
CLUTCH
Inspect and adjust●●Inspect housing, friction plate,
clutch plate and spring.
Replace●
TRANSMISSION
Replace oil●●Recommended brand: YA-
MALUBE
SAE10W-40
API service SG type or higher
JASO standard MA
Inspect●
Replace bearing●
SHIFT FORK, SHIFT CAM,
GUIDE BAR
Inspect●Inspect wear

3-8
ENGINE
LUBRICATING THE THROTTLE
1. Remove:
• Cap cover "1"
• Throttle cable cap "2"
2. Apply:
• Lithium soap base grease
On the throttle cable end "a", tube
guide cable winding portion "b"
and roller sliding surface "c".
3. Install:
• Throttle cable cap
• Cap cover
CLEANING THE AIR FILTER
ELEMENT
Proper air filter maintenance is the
biggest key to preventing premature
engine wear and damage.
Never run the engine without the
air filter element in place; this
would allow dirt and dust to enter
the engine and cause rapid wear
and possible engine damage.
1. Remove:
• Seat
• Fitting bolt "1"
• Washer "2"
• Air filter element "3"
• Air filter guide "4"2. Clean:
• Air filter element
Clean them with solvent.
After cleaning, remove the remaining
solvent by squeezing the element.
• Do not twist the element when
squeezing the element.
• Leaving too much of solvent in
the element may result in poor
starting.
3. Inspect:
• Air filter element
Damage→Replace.
4. Apply:
• Foam-air-filter oil or equivalent oil
to the element
Squeeze out the excess oil. Element
should be wet but not dripping.
5. Install:
• Air filter guide "1"
Align the projection "a" on filter guide
with the hole "b" in air filter element.
6. Apply:
• Lithium soap base grease
On the matching surface "a" on air
filter element.7. Install:
• Air filter element "1"
• Washer
• Fitting bolt
Align the projection "a" on filter guide
with the hole "b" in air filter case.
CHECKING THE TRANSMISSION
OIL LEVEL
1. Start the engine, warm it up for
several minutes and wait for five
minutes.
2. Place the machine on a level
place and hold it up on upright po-
sition by placing the suitable
stand under the engine.
3. Check:
• Transmission oil level
Transmission oil level checking
steps:
a. Remove the oil check bolt "1".
b. Inspect the oil level.
Be sure the machine is positioned
straight up when inspecting the oil
level.
Never attempt to remove the oil
check bolt just after high speed
operation. The heated oil could
spout out, causing danger. Wait
until the oil cools down.
Oil flows out→Oil level is correct.
Oil does not flow out→Oil level is
low. Add transmission oil until oil
flows out. Throttle cable cap:
1 Nm (0.1 m•kg, 0.7
ft•lb)
Fitting bolt:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Recommended brand:
YAMALUBE
Recommended engine
oil type
SAE10W-40
Recommended engine
oil grade
API service SG type or
higher
JASO standard MA

3-9
CHASSIS
c. Inspect the gasket (oil check bolt),
replace if damaged.
d. Tighten the oil check bolt.
CHANGING THE TRANSMISSION
OIL
1. Start the engine and warm it up
for several minutes and wait for
five minute.
2. Place the machine on a level
place and hold it on upright posi-
tion by placing the suitable stand
under the engine.
3. Place a suitable container under
the engine.
4. Remove:
• Oil drain bolt "1"
• Oil filler cap "2"
Drain the transmission oil.
5. Install:
• Aluminum washer
• Oil drain bolt "1"6. Fill:
• Transmission oil
7. Check:
• Oil leakage
8. Check:
• Transmission oil level
9. Install:
• Oil filler cap "2"
ADJUSTING THE PILOT SCREW
1. Adjust:
• Pilot air screw "1"
Adjustment steps:
a. Screw in the pilot air screw until it
is lightly seated.
b. Back out by the specified number
of turns.
ADJUSTING THE ENGINE IDLING
SPEED
1. Start the engine and thoroughly
warm it up.
2. Adjust:
• Engine idling speed
Adjustment steps:
a. Loosen the locknut "1".
b. Turn the throttle stop screw "2"
until the engine runs at the lowest
possible speed.
c. Tighten the locknut.
CHECKING THE EXHAUST PIPE
1. Inspect:
• O-ring "1"
Damage→Replace.
Install the O-rings with their de-
pressed "a" facing outward.
CHASSIS
BLEEDING THE HYDRAULIC
BRAKE SYSTEM
Bleed the brake system if:
• The system has been disassem-
bled.
• A brake hose has been loosened
or removed.
• The brake fluid is very low.
• The brake operation is faulty.
A dangerous loss of braking per-
formance may occur if the brake
system is not properly bled.
1. Remove:
• Brake master cylinder cap
• Diaphragm
• Reservoir float (front brake)
• Protector (rear brake)
2. Bleed:
• Brake fluid
Air bleeding steps:
a. Add proper brake fluid to the res-
ervoir.
b. Install the diaphragm. Be careful
not to spill any fluid or allow the
reservoir to overflow.
c. Connect the clear plastic tube "2"
tightly to the caliper bleed screw
"1". Oil check bolt:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Oil drain bolt:
20 Nm (2.0 m•kg, 14
ft•lb)
Recommended brand:
YAMALUBE
Recommended engine
oil type
SAE10W-40
Recommended engine
oil grade
API service SG type or
higher
JASO standard MA
Oil capacity (periodic oil
change):
0.66 L (0.58 Imp qt, 0.69
US qt)
Pilot air screw:
2-1/4 turns out
To increase idle speed→Turn the
throttle stop screw "2" in.
To decrease idle speed→Turn the
throttle stop screw "2" out.