2021 YAMAHA YFZ50 torque

9-11
92. 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)
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9-13
92. 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]
5. Clean the oil strainer with solvent.
6. Discard the old engine oil drain bolt O-ring, and then apply a thin coat of clean engine oil
to the new O-ring.
7. Install the oil strainer, the compression spring, the new O-ring and the engine oil
drain bolt. Tighten the engine oil drain bolt to
the specified torque. NOTICE: Before in-
stalling the engine oil drain bolt, be sure to
install the O-ring, compression spring and
oil strainer.
[ECB00322]
8. Refill with the specified amount of the recom- mended engine oil.
1. Oil strainer
2. Compression spring
3. O-ring
4. Engine oil drain bolt
1234
Tightening torque:Engine oil drain bolt:25 N

9-16
9
5. Install the transmission oil drain bolt and its
new gasket, and then tighten the bolt to the
specified torque.
6. Refill with the specified amount of the recom- mended oil. NOTICE: Make sure that no
foreign material enters the transmission
case.
[ECB03380]
7. Check the oil filler cap O-ring for damage, and replace it if necessary.
8. Install and tighten the oil filler cap.
9. Check the transmission case for oil leakage. If oil is leaking, check for the cause.EBU34111Cleaning the air filter elementThe air filter element should be serviced at the in-
tervals specified in the periodic maintenance
chart. Clean or, if necessary, replace the air filter
element more frequently if you are riding in unusu-
ally wet or dusty areas.TIPThere is a check hose at the bottom of the air filter
case. If dust or water collects in this hose, empty
the hose and clean the air filter element and air fil-
ter case.
1. Transmission oil drain bolt
2. GasketTightening torque:Transmission oil drain bolt:30 N

9-20
9
WARNING
EWB02342Always let the exhaust system cool prior to
touching exhaust components.
Do not start the engine with the spark arrester
removed. Sparks or exhaust particulate can
cause eye injury, burns, or start a fire. 1. Remove the tailpipe bolts.
2. Remove the tailpipe by pulling it out of themuffler, and then remove the gasket.
3. Tap the tailpipe lightly, and then use a wire brush to remove any carbon deposits from
the spark arrester portion of the tailpipe and
inside of the tailpipe housing.
4. Check the gasket for damage. Replace if nec- essary.
5. Install the gasket onto the tailpipe, then insert the tailpipe into the muffler and align the bolt
holes.
6. Install the bolts and tighten to the specified torque.
EBU23942Adjusting the carburetorThe carburetor should be checked and, if neces-
sary, adjusted at the intervals specified in the pe-
riodic maintenance chart. The carburetor is an
important part of the engine and requires very so-
phisticated adjustment. Therefore, most carbure-
tor adjustments should be left to a Yamaha dealer,
who has the necessary professional knowledge
and experience. The adjustment described in the
following section, however, may be performed by
the owner as part of routine maintenance.NOTICEECB00481The carburetor has been set and extensively
tested at the Yamaha factory. Changing these
settings without sufficient technical knowl-
edge may result in poor performance of or
damage to the engine. EBU24002Adjusting the engine idling speedThe engine idling speed must be checked and, if
necessary, adjusted as follows at the intervals
specified in the periodic maintenance chart.
Tightening torque:
Tailpipe bolt:10 N·m (1.0 kgf·m, 7.4 lb·ft)
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9-28
9
3. Loosen the locknut. 4. To tighten the drive chain, turn the drive chain
slack adjusting nut in direction (a). To loosen
the drive chain, turn the adjusting nut in direc-
tion (b) and push the rear wheels forward.
NOTICE: Improper drive chain slack will
overload the engine as well as other vital
parts of the ATV and can lead to drive
chain slippage or breakage. To prevent
this from occurring, keep the drive chain
slack within the specified limits.
[ECB00543]
5. Tighten the locknut, and then the bolts and nuts to their specified torques.
6. Adjust the rear brake lever free play. (See page 9-26.)
1. Rear brake lever free play adjusting nut
1. Drive chain slack adjusting nut
2. Locknut
1
1
2(a)(b)
Tightening torquesWLocknut:22 N

9-37
92. Lower the ATV to the ground.
3. Tighten the wheel bolts to the specified
torques.
EBU25721TroubleshootingAlthough Yamaha ATVs receive a thorough in-
spection before shipment from the factory, trouble
may occur during operation. Any problem in the
fuel, compression, or ignition systems, for exam-
ple, can cause poor starting and loss of power.
The following troubleshooting chart represents a
quick and easy procedure for checking these vital
systems yourself. However, should your ATV re-
quire any repair, take it to a Yamaha dealer, whose
skilled technicians have the necessary tools, ex-
perience, and know-how to service the ATV prop-
erly.
Use only genuine Yamaha replacement parts. Im-
itation parts may look like Yamaha parts, but they
are often inferior, have a shorter service life and
can lead to expensive repair bills.
WARNING
EWB02281Do not smoke when checking the fuel system.
Fuel can ignite or explode, causing severe inju-
ry or property damage. Make sure there are no
open flames or sparks in the area, including pi-
lot lights from water heaters or furnaces.
1. Arrow mark
2. Forward rotating direction
3. Wheel boltTightening torques:Front wheel bolt:45 N·m (4.5 kgf·m, 33 lb·ft)
Rear wheel bolt: 45 N·m (4.5 kgf·m, 33 lb·ft)3
1
2
UBW464E0.book Page 37 Thursday, January 23, 2020 2:42 PM