2020 YAMAHA YZ85 engine

Periodic maintenance an d a djustment
7-6
7
EAU84450
Checkin g the spark plu g
The 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 the spark plug cap.
2. Remove the spark plug as shown, with a spark plug wrench available
at a Yamaha dealer. 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).
TIP
If 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. Spark plug cap
1. Spark plug wrench
1
1
Specified spark plu g:
NGK/BR10EG
1. Spark plug gap
Spark plu g g ap:
0.5–0.6 mm (0.020–0.024 in)
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Periodic maintenance an d a djustment
7-7
7
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.
TIP
If 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 asshown.
EAU4144C
Transmission oil
The transmission must be checked for
oil leakage before each ride. If any
leakage is found, have a Yamaha deal-
er check and repair the motorcycle. In
addition, the transmission oil must be
changed at the intervals specified in
the periodic maintenance and lubrica-
tion chart.1. Start the engine, warm it up for several minutes, and then turn it
off.
2. Place the motorcycle on a level surface and hold it in an upright
position.
3. Place an oil pan under the trans- mission case to collect the used
oil.
4. Remove the transmission oil filler cap and its O-ring, and then re-
move the transmission oil drain
bolt and its gasket to drain the oil
from the transmission.
5. Install the drain bolt and its new gasket, and then tighten the bolt
to the specified torque.
Tightening torque:
Spark plug: 20 N·m (2.0 kgf·m, 15 lb·ft)
1. Spark plug cap
1
1. Transmission oil filler cap
2. O-ring
3. Transmission oil drain bolt
4. Gasket
1
2
43
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Periodic maintenance an d a djustment
7-8
7 6. Refill with the specified amount of
the recommended transmission
oil.
NOTICE
ECA10453
In or der to prevent clutch slip-
pa ge (since the transmission oil
also lu bricates the clutch), d o
not mix any chemical additives.
Do not use oils with a diesel
specification of “CD” or oils of a
hi gher quality than specifie d. In
a ddition, do not use oils la bele d
“ENERGY CONSERVING II” or
hi gher.
 Make sure that no forei gn mate-
rial enters the transmission.
7. Check the O-ring for damage, and replace it if necessary.
8. Install and tighten the transmis- sion oil filler cap and its O-ring.
9. 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.
EAU20071
Coolant
The coolant level should be checked
before each ride. In addition, the cool-
ant must be changed at the intervals
specified in the periodic maintenance
and lubrication chart.
EAUM1296To check the coolant level1. Place the vehicle on a level surfa- ce and hold it in an upright posi-
tion.
TIP
The coolant level must be
checked on a cold engine since
the level varies with engine tem-
perature.
 Make sure that the vehicle is posi-
tioned straight up when checking
the coolant level. A slight tilt to the
side can result in a false reading.
2. Remove the radiator cap and
check the coolant level in the radi-
ator. WARNING! Never attempt
to remove the ra diator cap
when the en gine is hot.
[EWA10382]
Ti ghtenin g torque:
Transmission oil drain bolt: 10 N·m (1.0 kgf·m, 7.4 lb·ft)
Recommen ded transmission oil:
Motor oil SAE 10W-30 type SE or
higher or Gear oil SAE 85W GL-3
Oil chan ge quantity:
0.50 L (0.53 US qt, 0.44 Imp.qt)
1. Radiator cap
1
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Periodic maintenance an d a djustment
7-9
7
TIP
The coolant should be at the bottom of
the radiator filler neck. The level will
change with variation of engine tem-
perature.
3. If the coolant is below the correct
coolant level, add coolant, and
then install the radiator cap.
NOTICE: If coolant is not avail-
a b le, use distille d water or soft
tap water instea d. Do not use
har d water or salt water since it
is harmful to the en gine. If water
has been used instead of cool-
ant, replace it with coolant as
soon as possi ble, otherwise the
coolin g system will not be pro-
tected against frost an d corro-
sion. If water has b een added to
the coolant, have a Yamaha
d ealer check the antifreeze con-
tent of the coolant as soon as
possi ble, otherwise the effec-
tiveness of the coolant will be
re duce d.
[ECA10473]
EAUM1318
To change the coolant
1. Place the vehicle on a level surfa- ce and let the engine cool if neces-
sary. 2. Place a container under the en-
gine to collect the used coolant.
3. Remove the radiator cap, and then the coolant drain bolt and its
gasket to drain the cooling sys-
tem. WARNING! Never attempt
to remove the ra diator cap
when the en gine is hot.
[EWA10382]
4. After the coolant is completely
drained, thoroughly flush the cool-
ing system with clean tap water.
5. Install the coolant drain bolt and its new gasket, and then tighten
the bolt to the specified torque.
1. Correct coolant level
1
1. Radiator cap
1. Coolant drain bolt
2. Gasket
Tightenin g torque:
Coolant drain bolt: 10 N·m (1.0 kgf·m, 7.4 lb·ft)
1
21
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Periodic maintenance an d a djustment
7-10
7 6. Pour the recommended coolant
into the radiator until it is full.
7. Install the radiator cap, start the engine, let it idle for several minu-
tes, and then turn it off.
8. Remove the radiator cap to check the coolant level in the radiator. If
necessary, add sufficient coolant
until it reaches the bottom of the
radiator filler neck, and then install
the radiator cap.
9. Start the engine, and then check the vehicle for coolant leakage. If
coolant is leaking, have a Yamaha
dealer check the cooling system.
EAU48393
Cleanin g the air filter element
The air filter element should be cleaned
or replaced at the intervals specified in
the periodic maintenance and lubrica-
tion chart. Clean or, if necessary, re-
place the air filter element more
frequently if you are riding in unusually
wet or dusty areas.
1. Remove the seat. (See page 4-8.)
2. Remove the air filter case cover as shown.
3. Remove the air filter element by removing the wing bolt and its
washer.
Antifreeze/water mixture ratio:1:1
Recommen ded antifreeze:
High-quality ethylene glycol anti-
freeze containing corrosion inhibi-
tors for aluminum engines
Coolant quantity:
Radiator (including all routes):0.55 L (0.58 US qt, 0.48 Imp.qt)
1. Air filter case cover
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Periodic maintenance an d a djustment
7-12
7 9. Install the air filter case cover in
the original position as shown.
10. Install the seat.
EAU42111
A djustin g the car buretor
The carburetor is an important part of
the engine and requires very sophisti-
cated adjustment. Therefore, most
carburetor adjustments should be left
to a Yamaha dealer, who has the nec-
essary professional knowledge and ex-
perience. The adjustment described in
the following section, however, may be
serviced by the owner as part of rou-
tine maintenance.
NOTICE
ECA10551
The car buretor has been set an d ex-
tensively teste d at the Yamaha fac-
tory. Chan gin g these settin gs
without sufficient technical knowl-
e dge may result in poor perfor-
mance of or d amage to the en gine.
1. Washer
1
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Periodic maintenance an d a djustment
7-13
7
EAU44391
A djustin g the eng ine idlin g
spee d
The engine idling speed must be ad-
justed when necessary.
1. Start the engine and thoroughly warm it up.
2. Turn the throttle stop screw until the engine runs at the lowest pos-
sible speed.
3. To increase the engine idling speed, turn the throttle stop screw
in direction (a). To decrease the
engine idling speed, turn the throt-
tle stop screw in direction (b).
EAU48434
Adjustin g the throttle grip free
play
Measure the throttle grip free play as
shown.
Periodically check the throttle grip free
play and, if necessary, adjust it as fol-
lows.
TIP
The engine idling speed must be cor-
rectly adjusted before checking and
adjusting the throttle grip free play.
1. Slide the rubber cover back.
2. Loosen the locknut.
3. To increase the throttle grip free
play, turn the adjusting nut in di-
rection (a). To decrease the throt-
tle grip free play, turn the adjusting
nut in direction (b).
1. Throttle stop screw
1. Throttle grip free play
Throttle grip free play:
3.0–6.0 mm (0.12–0.24 in)
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Periodic maintenance an d a djustment
7-21
7
EAU51721
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 master cylinders and calipers as
well as the brake hoses replaced at the
intervals listed below or whenever they
are damaged or leaking.
 Oil seals: Replace every two
years.
 Brake hoses: Replace every four
years.
EAU22762
Drive chain slack
The drive chain slack should be
checked before each ride and adjusted
if necessary.
EAU84400To check the d rive chain slack
1. Place the motorcycle on a suitable stand. (See page 7-28.)
2. Confirm the rear wheel is off the ground and the rear shock ab-
sorber is fully extended.
3. Shift the transmission into neutral.
4. Pull up the drive chain until the chain is taut, and then measure
distance A between the top of the
swingarm and the bottom of the
chain as shown.
5. If the drive chain slack is incorrect, adjust it as follows. NOTICE: Im-
proper drive chain slack will
overload the engine as well as
other vital parts of the motorcy-
cle an d can lead to chain slip-
pa ge or breakag e. To prevent
1. Distance A
Distance A:
58.0–68.0 mm (2.28–2.68 in) (YZ85,
YZ85L)
65.0–75.0 mm (2.56–2.95 in)
(YZ85LW, YZ85LWL)
1
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