2017 YAMAHA YS125 engine

Operation and important ri din g points
5-2
5
3. Start the engine by pushing the
start switch.
If the engine fails to start when us-
ing the start switch, release it, wait
a few seconds, and then try again.
Each starting attempt should be
as short as possible to preserve
the battery. Do not crank the en-
gine more than 10 seconds on any
one attempt.
NOTICE
ECA11043
For maximum en gine life, never ac-
celerate har d when the en gine is
col d!
EAU16673
Shiftin gShifting gears lets you control the
amount of engine power available for
starting off, accelerating, climbing hills,
etc.
The gear positions are shown in the il-
lustration.TIPTo shift the transmission into the neu-
tral position, press the shift pedal down
repeatedly until it reaches the end of its
travel, and then slightly raise it.
NOTICE
ECA10261
Even with the transmission in
the neutral position, d o not
coast for lon g period s of time
with the en gine off, an d d o not
tow the motorcycle for lon g d is-
tances. The transmission is
properly lu bricated only when
the en gine is runnin g. Ina de-
quate lu brication may d amage
the transmission.
 Always use the clutch while
chan gin g g ears to avoi d d am-
a g in g the en gine, transmission,
an d d rive train, which are not
d esi gne d to withstan d the
shock of force d shiftin g.
1. Shift pedal
2. Neutral position
1
N
2 3
4
5
1
2
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Operation and important rid ing points
5-3
5
EAU16811
Tips for re ducin g fuel con-
sumptionFuel consumption depends largely on
your riding style. Consider the follow-
ing tips to reduce fuel consumption:
 Shift up swiftly, and avoid high en-
gine speeds during acceleration.
 Do not rev the engine while shift-
ing down, and avoid high engine
speeds with no load on the en-
gine.
 Turn the engine off instead of let-
ting it idle for an extended length
of time (e.g., in traffic jams, at traf-
fic lights or at railroad crossings).
EAU16831
Engine break-inThere is never a more important period
in the life of your engine than the period
between 0 and 1000 km (600 mi). For
this reason, you should read the fol-
lowing material carefully.
Since the engine is brand new, do not
put an excessive load on it for the first
1000 km (600 mi). The various parts in
the engine wear and polish themselves
to the correct operating clearances.
During this period, prolonged full-throt-
tle operation or any condition that
might result in engine overheating
must be avoided.
EAU16883
0–150 km (0–90 mi)
Avoid prolonged operation above 4500
r/min.
After every hour of operation, stop the
engine, and then let it cool for five to
ten minutes.
Vary the engine speed from time to
time. Do not operate the engine at one
set throttle position. 150–500 km (90–300 mi)
Avoid prolonged operation above 5400
r/min.
Rev the engine freely through the
gears, but do not use full throttle at any
time.
500–1000 km (300–600 mi)
Avoid prolonged full-throttle operation.
Avoid prolonged operation above 7000
r/min.
NOTICE: After 1000 km (600
mi) of operation, the en gine oil must
b e chan ged an d the oil filter car-
tri dge or element replace d.
[ECA10303]
1000 km (600 mi) an d b eyon d
The vehicle can now be operated nor-
mally.NOTICE
ECA10311
 Keep the en gine spee d out of
the tachometer red zone.
 If any en gine trou ble shoul d oc-
cur during the en gine break-in
period , imme diately have a
Yamaha dealer check the vehi-
cle.
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Operation and important ri din g points
5-4
5
EAU17214
Parkin gWhen parking, stop the engine, and
then remove the key from the main
switch.
WARNING
EWA10312
Since the en gine an d exhaust
system can b ecome very hot,
park in a place where pe destri-
ans or chil dren are not likely to
touch them an d b e burne d.
 Do not park on a slope or on soft
groun d, otherwise the vehicle
may overturn, increasin g the
risk of a fuel leak an d fire.
 Do not park near grass or other
flamma ble materials which
mi ght catch fire.
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Periodic maintenance an d a djustment
6-1
6
EAU17246
Periodic inspection, adjustment, and
lubrication will keep your vehicle in the
safest and most efficient condition
possible. Safety is an obligation of the
vehicle owner/operator. The most im-
portant points of vehicle inspection,
adjustment, and lubrication are ex-
plained on the following pages.
The intervals given in the periodic
maintenance charts should be simply
considered as a general guide under
normal riding conditions. However, de-
pending on the weather, terrain, geo-
graphical location, and individual use,
the maintenance intervals may need to
be shortened.
WARNING
EWA10322
Failure to properly maintain the vehi-
cle or performin g maintenance ac-
tivities incorrectly may increase
your risk of injury or death durin g
service or while usin g the vehicle. If
you are not familiar with vehicle ser-
vice, have a Yamaha d ealer perform
service.
WARNING
EWA15123
Turn off the en gine when performin g
maintenance unless otherwise
specified .
 A runnin g en gine has movin g
parts that can catch on body
parts or clothin g an d electrical
parts that can cause shocks or
fires.
 Runnin g the en gine while ser-
vicin g can lead to eye injury,
b urns, fire, or car bon monoxi de
poisonin g – possi bly lea din g to
d eath. See pag e 1-3 for more in-
formation a bout car bon monox-
i d e.
WARNING
EWA15461
Brake discs, calipers, drums, and
linin gs can b ecome very hot d uring
use. To avoi d possi ble burns, let
b rake components cool before
touchin g them.
EAU17303
Emission controls not only function to
ensure cleaner air, but are also vital to
proper engine operation and maximum
performance. In the following periodic
maintenance charts, the services relat-
ed to emissions control are grouped
separately. These services require
specialized data, knowledge, and
equipment. Maintenance, replace-
ment, or repair of the emission control
devices and systems may be per-
formed by any repair establishment or
individual that is certified (if applicable).
Yamaha dealers are trained and equipped to perform these particular
services.
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Periodic maintenance an d a djustment
6-3
6
EAU71020
TIP The annual checks must b e performed every year, except if a kilometer- based maintenance, or for the UK, a
milea ge- base d maintenance, is performe d instead .
 From 30000 km (17500 mi), repeat the maintenance intervals starting from 6000 km (3500 mi).
 Items marked with an asterisk should be performed by a Yamaha dealer as they require special tools, data and tech-
nical skills.
EAU71040
Perio dic maintenance chart for the emission control systemNO. ITEM CHECK OR MAINTENANCE JOB ODOMETER READING
ANNUAL
CHECK
1000 km
(600 mi) 6000 km
(3500 mi) 12000 km
(7000 mi) 18000 km
(10500 mi) 24000 km
(14000 mi)
1 *Fuel line • Check fuel hoses for cracks or
damage.
• Replace if necessary. √√√√√
2 *Spark plu g • Check condition.
• Adjust gap and clean.
√√
• Replace. √√
3 *Valve clearance • Check and adjust. √√√√
4 *Fuel injection • Check and adjust engine idle
speed. √√√√√√
5 *Exhaust system • Check for leakage.
• Tighten if necessary.
• Replace gasket if necessary. √√√√√
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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
6-10
6
EAU78710
Checkin g the spark plugThe spark plug is an important engine
component, which is easy to check.
Since heat and deposits will cause any
spark plug to slowly erode, the spark
plug should be removed and checked
in accordance with the periodic main-
tenance and lubrication chart. In addi-
tion, the condition of the spark plug
can reveal the condition of the engine.
To remove the spark plu g
1. Remove cowling A. (See page 6-8.)
2. Remove the Y.R.C.S. (Yamaha Ram-Air Cooling System) cap by
removing the bolts and then, re-
move the spark plug cap. 3. Remove the spark plug as shown,
with the spark plug wrench includ-
ed in the owner’s tool kit. To check the spark plu
g
1. Check that the porcelain insulator around the center electrode of the
spark plug is a medium-to-light
tan (the ideal color when the vehi-
cle is ridden normally).
TIPIf the spark plug shows a distinctly dif-
ferent color, the engine could be oper-
ating improperly. Do not attempt to
diagnose such problems yourself. In-
stead, have a Yamaha dealer check
the vehicle.2. Check the spark plug for electrodeerosion and excessive carbon or
other deposits, and replace it if
necessary.
3. Measure the spark plug gap with a wire thickness gauge and, if nec-
essary, adjust the gap to specifi-
cation.
1. Cowling A
2. Y.R.C.S (Yamaha Ram–Air Cooling System) cap
3. Bolt
4. Spark plug cap
1. Spark plug wrench
4 32
1
1
Specified
spark plu g:
NGK/CPR8EA-9
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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