2018 YAMAHA YFM90 check engine

6-5
60–160 km (0–100 mi) or 0–10 hours
Avoid prolonged operation above 1/2 throttle.
Vary the speed of the ATV regularly. Do not oper-
ate it at one set throttle position.
160–320 km (100–200 mi) or 10–20 hours
Avoid prolonged operation above 3/4 throttle. Rev
the engine freely, but do not use full throttle at any
time.
320 km (200 mi) or 20 hours and beyond
The ATV can now be operated normally.
NOTICEECB00221If any engine trouble should occur during the
engine break-in period, immediately have a
Yamaha dealer check the ATV. EBU30021ParkingWhen parking the ATV, apply the rear brake lever,
shift the drive select lever into the forward posi-
tion, stop the engine, apply the parking brake, and
then turn the fuel cock to “OFF”.
EBU20765Parking on a slope
WARNING
EWB00832Avoid parking on hills or other inclines. Parking
on a hill or other incline could cause the ATV to
roll out of control, increasing the chance of an
accident. If you must park on an incline, place
the ATV transversely across the incline, shift
the drive select lever to the forward position,
stop the engine, apply the parking brake, and
then block the front and rear wheels with rocks
or other objects.1. Parking brake lock plate
1
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7-5
7Pre-operation checks
Always inspect your ATV before use to make sure
that it is safe operating condition. Perform the pre-
operation checks listed on page 5-1. Follow the
maintenance schedules and procedures as de-
scribed in the “Periodic Maintenance and Adjust-
ment” section of this manual.
WARNING! Failure
to inspect the ATV before riding it or failure to
maintain it properly increases the possibility of
an accident and equipment damage.
[EWB01433]
Speed limiter
For beginning riders, riders less experienced with
this model, or whenever limited speed is desir-
able, the throttle lever housing is equipped with a vehicle speed limiter. The speed limiter keeps the
throttle from fully opening, even when the throttle
lever is pushed to the maximum. Turning in the
adjusting screw limits the maximum engine power
available and decreases the maximum speed of
the ATV. Turning in the adjusting screw decreases
top speed, and turning it out increases top speed.
(See page 4-3.)
This model also has an engine speed limiter plate
to limit the amount of engine power available.
Yamaha recommends that all beginning riders start off with the engine speed limiter plate in-
stalled and the vehicle speed limiter adjusting
screw turned in to limit the amount of speed avail-
able while they learn. The vehicle speed limiter
may be gradually adjusted to increase maximum
speed as the beginner becomes more familiar with
operating the ATV. Parents should decide when to
adjust the ATV for more power as their young-
ster’s riding skills improve. Once the ATV rider can
operate with skill at the top speed permitted by
adjusting the vehicle speed limiter alone, the en-
gine speed limiter plate can be removed. Since re-
moval of this plate will result in a significant
increase in power, turn the vehicle speed limiter
adjusting screw back in again and adjust it out inUBD362E0.book Page 5 Tuesday, January 31, 2017 5:10 PM

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. √√√
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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

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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
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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)
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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
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