
Table of contentsSafety information ............................ 1-1
Description ....................................... 2-1
Left view ......................................... 2-1
Right view ....................................... 2-2
Controls and instruments ............... 2-3
Instrument an d control functions ... 3-1
Main switch/steering lock............... 3-1
Indicator lights and warning light ............................................. 3-2
Multi-function meter unit ................ 3-3
Handlebar switches ........................ 3-5
Clutch lever .................................... 3-6
Shift pedal ...................................... 3-6
Brake lever...................................... 3-7
Brake pedal .................................... 3-7
Fuel tank cap .................................. 3-8
Fuel ................................................. 3-8
Catalytic converters ..................... 3-10
Seat .............................................. 3-11
Adjusting the shock absorber assemblies ................................ 3-11
Sidestand ..................................... 3-12
Ignition circuit cut-off system ....... 3-13 For your safety – pre-operation
checks
............................................... 4-1
Operation an d important ri din g
points ................................................. 5-1
Starting the engine .......................... 5-1
Shifting ............................................ 5-2
Tips for reducing fuel consumption ................................ 5-3
Engine break-in ............................... 5-3
Parking ............................................ 5-4
Perio dic maintenance an d
a d justment ........................................ 6-1
Owner’s tool kit ............................... 6-2
Periodic maintenance chart for the emission control system .............. 6-3
General maintenance and lubrication chart ........................... 6-4
Removing and installing the
cowling and panels ...................... 6-8
Checking the spark plug ............... 6-10
Engine oil and oil filter element ..... 6-11
Cleaning the air filter element and cleaning the check hose ............ 6-14
Adjusting the engine idling
speed ......................................... 6-16
Checking the throttle grip free play ............................................ 6-16
Valve clearance ............................. 6-17
Tires .............................................. 6-17 Cast wheels .................................. 6-19
Adjusting the clutch lever free
play ............................................ 6-19
Checking the brake lever free play ............................................ 6-20
Adjusting the brake pedal free play ............................................ 6-21
Brake light switches ..................... 6-21
Checking the front brake pads
and rear brake shoes ............... 6-22
Checking the brake fluid level ...... 6-22
Changing the brake fluid ............. 6-23
Drive chain slack........................... 6-24
Cleaning and lubricating the
drive chain ................................. 6-25
Checking and lubricating the cables ........................................ 6-26
Checking and lubricating the throttle grip and cable ............... 6-26
Checking and lubricating the
brake and shift pedals............... 6-26
Checking and lubricating the brake and clutch levers ............. 6-27
Checking and lubricating the centerstand and sidestand........ 6-28
Lubricating the swingarm
pivots......................................... 6-28
Checking the front fork ................. 6-29
Checking the steering................... 6-29
Checking the wheel bearings ....... 6-30
Battery .......................................... 6-30UBT4E0E0.book Page 1 Thursday, November 17, 2016 10:55 AM

For your safety – pre-operation checks
4-1
4
EAU15599
Inspect your vehicle each time you use it to make sure the vehicle is in safe operating condition. Always follow the inspection
and maintenance procedures and schedules described in the Owner’s Manual.
WARNING
EWA11152
Failure to inspect or maintain the vehicle properly increases the possibility of an acci dent or equipment damag e.
Do not operate the vehicle if you fin d any pro blem. If a pro blem cannot be corrected b y the proce dures provi ded in
this manual, have the vehicle inspecte d b y a Yamaha dealer.Before using this vehicle, check the following points:
ITEM CHECKS PAGE
Fuel • Check fuel level in fuel tank.
• Refuel if necessary.
• Check fuel line for leakage. 3-8
En gine oil • Check oil level in engine.
• If necessary, add recommended oil to specified level.
• Check vehicle for oil leakage. 6-11
Front brake • Check operation.
• If soft or spongy, have Yamaha dealer bleed hydraulic system.
• Check brake pads for wear.
• Replace if necessary.
• Check fluid level in reservoir.
• If necessary, add specified brake fluid to specified level.
• Check hydraulic system for leakage. 6-22, 6-22
Rear brake • Check operation.
• Check pedal free play.
• Adjust if necessary. 6-21, 6-22
Clutch • Check operation.
• Lubricate cable if necessary.
• Check lever free play.
• Adjust if necessary. 6-19
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Periodic maintenance an d a djustment
6-6
6
19 Shift pe
dal pivot
shaft • Lubricate with lithium-soap-
based grease. √√√√√
20 *Unifie
d b rake sys-
tem • Check cable free play, and adjust
if necessary. √√√√√√
• Lubricate link pivot of brake pedal with lithium-soap-based grease. √√√√√
21 Si
destan d, center-
stan d • Check operation.
• Lubricate with lithium-soap-
based grease. √√√√√
22 *Sidestan d switch • Check operation and replace if
necessary. √√√√√√
23 *Front fork • Check operation and for oil leak-
age.
• Replace if necessary. √√√√
24 *Shock a
bsor ber as-
sem blies • Check operation and for oil leak-
age.
• Replace if necessary. √√√√
25 En gine oil • Change (warm engine before
draining).
• Check oil level and vehicle for oil leakage. √√√√√√
26 En
gine oil filter ele-
ment •Replace.
√√√
27 *Front an
d rear
b rake switches • Check operation.
√√√√√√
28 *Movin
g parts an d
ca bles • Lubricate.
√√√√√
NO. ITEM CHECK OR MAINTENANCE JOB
OD OMETER READING
ANNUAL
CHECK
1000 km
(600 mi) 6000 km
(3500 mi) 12000 km
(7000 mi) 18000 km
(10500 mi) 24000 km
(14000 mi)
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Periodic maintenance an d a djustment
6-11
6
To install the spark plu g
1. Clean the surface of the spark plug gasket and its mating surfa-
ce, and then wipe off any grime
from the spark plug threads.
2. Install the spark plug with the spark plug wrench, and then tight-
en it to the specified torque.
TIPIf a torque wrench is not available
when installing a spark plug, a good
estimate of the correct torque is 1/4–
1/2 turn past finger tight. However, the
spark plug should be tightened to the
specified torque as soon as possible.3. Install the spark plug cap.
4. Install the Y.R.C.S. (Yamaha Ram-Air Cooling System) cap by install-
ing the bolts.
5. Install the cowling.
EAU78803
En gine oil an d oil filter ele-
mentThe engine oil level should be checked
before each ride. In addition, the oil
must be changed and the oil filter ele-
ment replaced at the intervals specified
in the periodic maintenance and lubri-
cation chart.
To check the en gine oil level
1. Place the vehicle on the center- stand. A slight tilt to the side can
result in a false reading.
2. Start the engine, warm it up for several minutes, and then turn it
off.
3. Wait a few minutes until the oil set- tles, remove the engine oil filler
cap, wipe the dipstick clean, insert
it back into the oil filler hole (with-
out screwing it in), and then re-
move it again to check the oil level.
WARNING! Never remove the
engine oil filler cap after hi gh-
speed operation, otherwise hot
en gine oil coul d spout out an d
cause damag e or injury. Always
let the en gine oil cool down suf-
1. Spark plug gapSpark plu g g ap:
0.8–0.9 mm (0.031–0.035 in)
Ti ghtenin g torque:
Spark plug: 13 N·m (1.3 kgf·m, 9.4 lb·ft)
UBT4E0E0.book Page 11 Thursday, November 17, 2016 10:55 AM
![YAMAHA YS125 2017 Owners Manual Periodic maintenance an d a djustment
6-12
6
ficiently
before removin g the oil
filler cap.
[EWA17640]
NOTICE: Do not
operate the vehicle until you
know that the en gine oil level is
sufficient.
YAMAHA YS125 2017 Owners Manual Periodic maintenance an d a djustment
6-12
6
ficiently
before removin g the oil
filler cap.
[EWA17640]
NOTICE: Do not
operate the vehicle until you
know that the en gine oil level is
sufficient.](/manual-img/51/53875/w960_53875-46.png)
Periodic maintenance an d a djustment
6-12
6
ficiently
before removin g the oil
filler cap.
[EWA17640]
NOTICE: Do not
operate the vehicle until you
know that the en gine oil level is
sufficient.
[ECA10012]
TIPThe engine oil should be between the
minimum and maximum level marks.4. If the engine oil is below the mini- mum level mark, add sufficient oil
of the recommended type to raise
it to the correct level.
5. Check the O-ring for damage, and replace it if necessary.
6. Install and tighten the engine oil filler cap.
To chan ge the en gine oil (with or
without oil filter element replace-
ment) 1. Start the engine, warm it up for several minutes, and then turn it
off.
2. Place an oil pan under the engine to collect the used oil.
3. Remove the engine oil filler cap, the engine oil drain bolt and its
gasket to drain the oil from the
crankcase.
TIPSkip steps 4–6 if the oil filter element is
not being replaced.4. Remove the oil filter element coverby removing the bolts.
1. Engine oil filler cap
1. O-ring
2. Engine oil dipstick
3. Maximum level mark
4. Minimum level mark
1
4 321
1. Engine oil drain bolt
2. Gasket
1. Bolt
2. Oil filter element cover
12
1
2
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Periodic maintenance an d a djustment
6-14
6
3. Loosen the bleed bolt, start the
engine and keep it idling until oil
flows out. If no oil comes out after
several minutes, turn the engine
off immediately and consult a
Yamaha dealer for inspection.
4. After checking the oil pressure, tighten the bleed bolt with the
specified torque.
5. Install the Y.R.C.S. (Yamaha Ram- Air Cooling System) cap.
6. Install the cowling. 7. Start the engine, and then let it idle
for several minutes while checking
it for oil leakage. If oil is leaking,
immediately turn the engine off
and check for the cause.
8. Turn the engine off, check the oil level and correct it if necessary.
EAUW3321
Cleanin g the air filter element
an d cleanin g the check hoseThe air filter element should be cleaned
at the intervals specified in the periodic
maintenance and lubrication chart.
Clean the air filter element more fre-
quently if you are riding in unusually
wet or dusty areas. In addition, the air
filter check hose must be frequently
checked and cleaned if necessary.
To clean the air filter element
1. Remove panel A. (See page 6-8.)
2. Remove the air filter case cover by removing the screws, and then
pull the air filter element out.
1. Bleed boltTightenin g torque:
Bleed bolt: 7 N·m (0.7 kgf·m, 5.1 lb·ft)
1
1. Air filter case cover
2. Screw
2 2
1
UBT4E0E0.book Page 14 Thursday, November 17, 2016 10:55 AM

Periodic maintenance an d a djustment
6-23
6
Insufficient brake flui d may al-
low air to enter the b rake sys-
tem, re ducin g brakin g
performance.
Clean the filler cap before re-
moving . Use only DOT 4 b rake
flui d from a seale d container.
Use only the specified b rake flu-
i d ; otherwise, the ru bber seals
may deteriorate, causin g leak-
a g e.
Refill with the same type of
brake flui d. A ddin g a brake flui d
other than DOT 4 may result in a
harmful chemical reaction.
Be careful that water does not
enter the brake flui d reservoir
when refillin g. Water will si gnifi-
cantly lower the boilin g point of
the flui d an d may result in vapor
lock.
NOTICE
ECA17641
Brake flui d may damag e painted
surfaces or plastic parts. Always
clean up spille d flui d imme diately.
As the brake pads wear, it is normal for
the brake fluid level to gradually go
down. A low brake fluid level may indi-
cate worn brake pads and/or brake
system leakage; therefore, be sure to
check the brake pads for wear and the
brake system for leakage. If the brake
fluid level goes down suddenly, have a
Yamaha dealer check the cause before further riding.
EAU22724
Chan gin g the brake flui d Have a Yamaha dealer change the
brake fluid at the intervals specified in
the periodic maintenance and lubrica-
tion chart. In addition, have the oil seals
of the brake master cylinder and cali-
per as well as the brake hose replaced
at the intervals listed below or whenev-
er they are damaged or leaking.
Oil seals: Replace every two
years.
Brake hose: Replace every four
years.
UBT4E0E0.book Page 23 Thursday, November 17, 2016 10:55 AM

Periodic maintenance an d a djustment
6-29
6
EAU23273
Checkin g the front forkThe condition and operation of the
front fork must be checked as follows
at the intervals specified in the periodic
maintenance and lubrication chart.
To check the con dition
Check the inner tubes for scratches,
damage and excessive oil leakage.
To check the operation 1. Place the vehicle on a level surfa- ce and hold it in an upright posi-
tion. WARNING! To avoi d injury,
securely support the vehicle so
there is no dan ger of it fallin g
over.
[EWA10752]
2. While applying the front brake, push down hard on the handle-
bars several times to check if the
front fork compresses and re-
bounds smoothly.
NOTICE
ECA10591
If any d amage is foun d or the front
fork does not operate smoothly,
have a Yamaha dealer check or re-
pair it.
EAU45512
Checkin g the steerin gWorn or loose steering bearings may
cause danger. Therefore, the operation
of the steering must be checked as fol-
lows at the intervals specified in the
periodic maintenance and lubrication
chart.
1. Place the vehicle on the center- stand. WARNING! To avoi d inju-
ry, securely support the vehicle
so there is no dan ger of it fallin g
over.
[EWA10752]
2. Hold the lower ends of the front fork legs and try to move them for-
ward and backward. If any free
play can be felt, have a Yamaha
dealer check or repair the steer-
ing.
UBT4E0E0.book Page 29 Thursday, November 17, 2016 10:55 AM