YAMAHA YFM90R 2021 Manual Online

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EBU33902Owner’s Manual and tool kitPlace the Owner’s Manual in a plastic bag, and
along with the tool kit, store it on the bottom of the
seat.
The information included in this manual and the
tools provided in the tool kit are intended to assist
you in the performance of preventive maintenance
and minor repairs. However, additional tools are
necessary to perform certain maintenance work
correctly.TIPThere is a tire pressure gauge in the tool kit. 
If you do not have the tools or experience re-
quired for a particular job, have a Yamaha deal-
er perform it for you.

1. Tool kit
2. Owner’s Manual
1
2
UBD365E0.book Page 2 Monday, January 27, 2020 9:05 AM

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EBU21747Periodic maintenance chart: Emission control systemTIPFor ATVs not equipped with an odometer or an hour meter, follow the month maintenance intervals in-
stead.
 For odometer or hour meter-equipped vehicles, follow the month maintenance interval if the ATV isn’t
ridden for the stated mileage or engine operating hours.
 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. √√√
UBD365E0.book Page 3 Monday, January 27, 2020 9:05 AM

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6*Exhaust system • Check for leakage and replace gasket(s) if neces-
sary.
• Check for looseness and tighten all screw clamps and joints if necessary. √√√
7Spark arrester • Clean. √√√
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
UBD365E0.book Page 4 Monday, January 27, 2020 9:05 AM

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EBU2186EPeriodic maintenance chart: General maintenance and lubricationTIPFor ATVs not equipped with an odometer or an hour meter, follow the month maintenance intervals in-
stead.
 For odometer or hour meter-equipped vehicles, follow the month maintenance interval if the ATV isn’t
ridden for the stated mileage or engine operating hours.
 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 Air filter element • Clean and replace if necessary. Every 20–40 hours (more often in wet or
dusty areas)
2 Air filter check hose • Clean. √√√√√
3 *Front brake • Check operation and correct if necessary.
• Check brake lever free play and adjust if neces-
sary. √√√√√
• Replace brake shoes. Whenever worn to the limit
4 *Rear brake • Check operation and correct if necessary.
• Check brake lever free play and adjust if neces-
sary. √√√√√
• Replace brake shoes. Whenever worn to the limit
UBD365E0.book Page 5 Monday, January 27, 2020 9:05 AM

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5*Wheels • Check runout and for damage, and replace if nec-
essary. √ √√√
6 *Tires • Check tread depth and for damage, and replace if
necessary.
• Check air pressure and balance, and correct if necessary. √ √√√
7 *Wheel hub bearings • Check for looseness or damage, and replace if
necessary. √ √√√
8 *Front arm pivots • Lubricate with lithium-soap-based grease. √√√
9 Drive chain • Check chain slack and adjust if necessary.
• Check rear wheel alignment and correct if neces-
sary.
• Clean and lubricate. √√√√√
10 *Drive chain rollers • Check for wear and replace if necessary. √√√
11 *V- b e l t • Check for wear, cracks or other damage, and re-
place if necessary. √ √√√
12 *Chassis fasteners • Make sure that all nuts, bolts, and screws are
properly tightened. √√√√√
13 *Shock absorber as-
semblies • Check operation and correct if necessary.
• Check for oil leakage and replace if necessary.
√√√
14 *Front knuckle piv-
ots • Lubricate with lithium-soap-based grease.
√√√
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
UBD365E0.book Page 6 Monday, January 27, 2020 9:05 AM

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15*Steering shaft • Lubricate with lithium-soap-based grease. √√√
16 *Steering system • Check operation and repair or replace if dam-
aged.
• Check toe-in and adjust if necessary. √√√√√
17 Engine oil • Change.
• Check ATV for oil leakage, and correct if neces-
sary. √ √√√
18 Engine oil strainer • Clean. √√√
19 Transmission oil • Change.
• Check ATV for oil leakage, and correct if neces-
sary. √√
20 *Moving parts and
cables • Lubricate.
√√√√
21 *Throttle lever • Check operation.
• Check throttle lever free play, and adjust if neces-
sary.
• Lubricate cable and lever housing. √√√√√
22 *Brake switch • Check operation and correct if necessary. √√√√√
23 *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 320UBD365E0.book Page 7 Monday, January 27, 2020 9:05 AM

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EBU23062TIPSome maintenance items need more frequent service if you are riding in unusually wet, dusty, sandy or
muddy areas, or at full-throttle. UBD365E0.book Page 8 Monday, January 27, 2020 9:05 AM

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EBU23216Checking 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 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 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).
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.
1. Spark plug cap
1
1. Spark plug wrench
1
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2. Check the spark plug for electrode erosion
and 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 plug
1. 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.
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.EBU37001Engine 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
chart.
Specified spark plug:
NGK/CR6HSA
1. Spark plug gapSpark plug gap:0.6–0.7 mm (0.024–0.028 in)
Tightening torque:Spark plug:12 N·m (1.2 kgf·m, 8.9 lb·ft)
UBD365E0.book Page 10 Monday, January 27, 2020 9:05 AM

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9To check the engine oil level
1. Park the ATV on a level surface.
2. Wait for the engine to cool.
TIPIf the engine was started before checking the oil
level, wait 10 minutes. This will allow oil to settle
into the crankcase for an accurate reading. 3. Remove the engine oil filler cap and wipe the dipstick 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. 5. If the engine oil is at or below the minimum
level mark, add sufficient quantity of the rec-
ommended engine oil. 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. Park the ATV on a level surface.
1. Engine oil filler cap
1
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
UBD365E0.book Page 11 Monday, January 27, 2020 9:05 AM