check engine YAMAHA YFM90 2018 User Guide

7-8
7
modifications may cause changes in handling
which in some situations could lead to an acci-
dent.
[EWB01492]
Exhaust system
WARNING
EWB01502
Dry grass or brush or other combustible ma-
terial accumulated around the engine area
could catch fire. Do not operate, idle, or park
the ATV in dry grass or other dry ground cov-
er. Keep the engine area free of dry grass,
brush, or other combustible material.
 Someone touching the exhaust system dur-
ing or after operation could be burned. Do
not touch the hot exhaust system. Do not
park the ATV in a place where others might
be likely to touch it. The muffler and other engine parts become ex-
tremely hot during operation and remain hot after
the engine has stopped. To reduce the risk of fire
during operation or after leaving the ATV, do not
let brush, grass and other materials collect under
the vehicle, near the muffler or exhaust pipe, or
next to other hot parts. Check under the vehicle
after operating in areas where combustible mate- rials may have collected. Do not idle or park the
vehicle in long dry grass or other dry ground cov-
er.
To prevent burns, avoid touching the exhaust sys-
tem. Park the ATV in a place where pedestrians or
children are not likely to touch it.UBD362E0.book Page 8 Tuesday, January 31, 2017 5:10 PM

8-3
8
EBU21745Periodic maintenance chart for the emission control systemTIPFor ATVs not equipped with an odometer or an hour meter, follow the month maintenance intervals.
 For ATVs equipped with an odometer or an hour meter, follow the km (mi) or hours maintenance inter-
vals. However, keep in mind that if the ATV isn’t used for a long period of time, the month maintenance
intervals should still be followed.
 Items marked with an asterisk should be performed by a Yamaha dealer as they require special tools,
data and technical skills. NO. ITEM CHECK OR MAINTENANCE
JOB INITIAL
EVERY
Whichev-
er comes first month136612
km (mi) 320
(200) 1300
(800) 2500
(1600) 2500
(1600) 5000
(3200)
hours 20 80 160 160 320
1 *Fuel line • Check fuel hoses for cracks or other damage, and
replace if necessary. √√√
2 Spark plug • Check condition and clean, regap, or replace if
necessary. √√√√√
3 *Va l ve s • Check valve clearance and adjust if necessary. √ √√√
4 *Carburetor • Check starter (choke) operation and correct if
necessary.
• Check engine idling speed and adjust if neces- sary. √√√√
5 *Crankcase breath-
er system • Check breather hose for cracks or other damage,
and replace if necessary. √√√
UBD362E0.book Page 3 Tuesday, January 31, 2017 5:10 PM

8-7
8
15*Steering system • Check operation and repair or replace if dam-
aged.
• Check toe-in and adjust if necessary. √√√√√
16 Engine oil • Change.
• Check ATV for oil leakage, and correct if neces-
sary. √ √√√
17 Engine oil strainer • Clean. √√√
18 Transmission oil • Change.
• Check ATV for oil leakage, and correct if neces-
sary. √√
19 *Moving parts and
cables
• Lubricate.
√√√√
20 *Throttle lever • Check operation.
• Check throttle lever free play, and adjust if neces-
sary.
• Lubricate cable and lever housing. √√√√√
21 *Brake switch • Check operation and correct if necessary. √√√√√
22 *Switches • Check operation and correct if necessary. √√√√√
NO. ITEM
CHECK OR MAINTENANCE
JOB INITIAL EVERY
Whichev-
er comes first month136612
km (mi) 320
(200) 1300
(800) 2500
(1600) 2500
(1600) 5000
(3200)
hours 20 80 160 160 320UBD362E0.book Page 7 Tuesday, January 31, 2017 5:10 PM

8-9
8
EBU23214Checking 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 ac-
cordance with the periodic maintenance and lubri-
cation chart. In addition, the condition of the spark
plug can reveal the condition of the engine.
To remove the spark plug1. Remove the spark plug cap. 2. Remove the spark plug as shown, with the
spark plug wrench included in the owner’s
tool kit.
To check the spark plug 1. Check that the porcelain insulator around the center electrode of the spark plug is a medi-
um-to-light tan (the ideal color when the ATV
is ridden normally).1. Spark plug cap
1
1. Spark plug wrench
1
UBD362E0.book Page 9 Tuesday, January 31, 2017 5:10 PM

8-10
8
TIPIf the spark plug shows a distinctly different color,
the engine could be operating improperly. Do not
attempt to diagnose such problems yourself. In-
stead, have a Yamaha dealer check the ATV. 2. Check the spark plug for electrode erosionand excessive carbon or other deposits, and
replace it if necessary.
3. Measure the spark plug gap with a wire thick- ness gauge and, if necessary, adjust the gap
to specification.
To install the spark plug1. Clean the surface of the spark plug gasket and its mating surface, and then wipe off any
grime from the spark plug threads.
2. Install the spark plug with the spark plug wrench, and then tighten it to the specified
torque.
Specified spark plug:
NGK/CR6HSA
1. Spark plug gapSpark plug gap:0.6–0.7 mm (0.024–0.028 in)
UBD362E0.book Page 10 Tuesday, January 31, 2017 5:10 PM

8-11
8
TIPIf a torque wrench is not available when installing
the 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 speci-
fied torque as soon as possible. 3. Install the spark plug cap.EBU37000Engine oilThe engine oil level should be checked before
each ride. In addition, the oil must be changed at
the intervals specified in the periodic maintenance
and lubrication chart.
To check the engine oil level1. Place the ATV on a level surface.
2. Check the engine oil level on a cold engine.
TIPIf the engine was started before checking the oil
level, warm up the engine and then wait at least
ten minutes until the oil settles for an accurate
reading. 3. Remove the engine oil filler cap, and then wipe the engine oil dipstick off with a clean
rag.
4. Insert the dipstick into the filler hole, screw it in, and then remove it again to check the oil
level.
Tightening torque:
Spark plug:12 N·m (1.2 kgf·m, 8.9 lb·ft)1. Engine oil filler cap
1
UBD362E0.book Page 11 Tuesday, January 31, 2017 5:10 PM

8-12
8
TIPThe engine oil should be between the minimum
and maximum level marks. 5. If the engine oil is at or below the minimumlevel mark, add sufficient oil of the recom-
mended type to raise it to the correct level.
NOTICE: Be sure the engine oil is at the
correct level, otherwise engine damage
may result.
[ECB00852]
6. Check the O-ring for damage, and then insert the dipstick and tighten the engine oil filler
cap.
To change the engine oil 1. Place the ATV on a level surface.
2. Start the engine, warm it up for several minu- tes, and then turn it off.
3. Place an oil pan under the engine to collect the used oil.
4. Remove the engine oil filler cap, and then re- move the engine oil drain bolt to drain the oil
from the crankcase. NOTICE: When remov-
ing the engine oil drain bolt, the compres-
sion spring, oil strainer and O-ring will fall
out. Take care not to lose these parts.
[ECB00312]
1. Engine oil filler cap
2. O-ring
3. Engine oil dipstick
4. Maximum level mark
5. Minimum level mark
1
4
5 3 2
UBD362E0.book Page 12 Tuesday, January 31, 2017 5:10 PM

8-14
8
9. Check the engine oil filler cap O-ring for dam-
age, and then install and tighten the engine oil
filler cap.
10. 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.
11. Turn the engine off, wait at least ten minutes, and then check the oil level and correct it if
necessary.
EBU34472Transmission oilThe transmission case must be checked for oil
leakage before each ride. If any leakage is found,
have a Yamaha dealer check and repair the ATV.
In addition, the transmission oil must be changed
at the intervals specified in the periodic mainte-
nance and lubrication chart.
To change the transmission oil1. Place the ATV on a level surface.
2. Place an oil pan under the transmission case to collect the used oil.
3. Remove the transmission oil filler cap and its O-ring from the transmission case. 4. Remove the transmission oil drain bolt and its
gasket to drain the oil from the transmission
case.
1. Transmission oil filler cap
2. O-ring12
UBD362E0.book Page 14 Tuesday, January 31, 2017 5:10 PM

8-16
8
1. Park the ATV on a level surface.
2. Remove the seat. (See page 4-12.)
3. Remove the air filter case cover by unhooking
the air filter case cover holders. 4. Remove the air filter element, and clean it with
solvent. WARNING! Always use parts
cleaning solvent to clean the air filter ele-
ment. Never use low-flash-point solvents
or gasoline to clean the air filter element
because the engine could catch fire or ex-
plode.
[EWB03540]
1. Air filter case check hose
1
1. Air filter case cover
2. Air filter case cover holder
1
2
UBD362E0.book Page 16 Tuesday, January 31, 2017 5:10 PM

8-17
85. Squeeze the excess solvent out of the air filter
element and let it dry. NOTICE: Do not twist
the air filter element when squeezing it.
[ECB02310]
6. Check the air filter element and replace it if damaged.
7. Apply Yamaha foam air filter oil or other qual- ity foam air filter oil to the element.TIPThe air filter element should be wet but not drip-
ping. 8. Insert the air filter element into the air filtercase.
9. Install the air filter case cover by hooking the holders onto the air filter case. NOTICE:
Make sure that the air filter element is
properly seated in the air filter case. Never
operate the engine with the air filter ele-
1. Air filter element
1
UBD362E0.book Page 17 Tuesday, January 31, 2017 5:10 PM