Piston YAMAHA YZ65 2021 Owners Manual

Instrument and control functions
4-5
4
Gasoline
This model’s engine is designed to use
premium unleaded gasoline with a
pump octane number [(R+M)/2] of 91
or higher, or a research octane number
(RON) of 95 or higher. If knocking or
pinging occurs, try a gasoline of a dif-
ferent brand.
NOTICE
ECA15591
Use only unlea
ded g asoline. The use
of lead ed g asoline will cause severe
d ama ge to internal en gine parts,
such as the piston rin gs as well as to
the exhaust system.
Gasohol
There are two types of gasohol: gaso-
hol containing ethanol and that con-
taining methanol. Gasohol containing
ethanol can be used if the ethanol con-
tent does not exceed 10% (E10). Gas-
ohol containing methanol should not
be used as it can cause engine or fuel
system problems.
Fillin g the fuel tank
WARNING
EWA10882
Gasoline an d gasoline vapors are
extremely flamma ble. To avoi d fires
an d explosions an d to re duce the
risk of injury when refueling , follow
these instructions.
1. Before refueling, turn off the en- gine and be sure that no one is sit-
ting on the vehicle. Never refuel
while smoking, or while in the vi-
cinity of sparks, open flames, or
other sources of ignition such as
the pilot lights of water heaters
and clothes dryers.
2. Do not overfill the fuel tank. Stop filling when the fuel reaches the
bottom of the filler tube. Because
fuel expands when it heats up,
heat from the engine or the sun
can cause fuel to spill out of the
fuel tank.
3. Wipe up any spilled fuel immedi- ately. NOTICE: Immediately
wipe off spille d fuel with a clean,
d ry, soft cloth, since fuel may
d eteriorate painte d surfaces or
plastic parts.
[ECA10072]
4. Be sure to securely close the fuel tank cap.
WARNING
EWA15152
Gasoline is poisonous an d can
cause injury or death. Han dle gaso-
line with care. Never siphon gasoline
b y mouth. If you shoul d swallow
some gasoline or inhale a lot of gas-
oline vapor, or get some gasoline in
your eyes, see your d octor immedi-
ately. If g asoline spills on your skin,
1. Maximum fuel level
2. Fuel tank filler tube
12
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Operation and important ri din g points
6-2
6
the higher gears and check the
full-throttle response. Stop the en-
gine and check the spark plug.
5. After again allowing the engine to cool, restart and run the motorcy-
cle for 5 more minutes. Full throttle
and the higher gears may be used,
but sustained full-throttle opera-
tion should be avoided. Stop the
engine and check the spark plug
again.
6. Allow the engine to cool, remove the cylinder head and cylinder,
and inspect the piston and cylin-
der. Remove any high spots on
the piston with #600-grit wet
sandpaper. Clean all components
and carefully reassemble the cyl-
inder head and cylinder.
7. Drain the break-in oil-fuel mixture from the fuel tank and refill with
the normal oil-fuel mixture. (See
page 4-4.)
8. Start the engine and check its power delivery and throttle re-
sponse throughout all gear rang-
es. Stop the engine and check the
spark plug condition. It should be-
gin to lighten in color.
9. Restart the motorcycle and ride it for about 10 to 15 more minutes.
Stop the engine and check the
spark plug condition. (See page
7-6.)
10. Lastly, thoroughly check the mo- torcycle for loose parts, oil leak-
age and any other problems.
Check all fittings and fasteners
and tighten as necessary.
TIP
Be sure to inspect and make adjust-
ments thoroughly. In particular, check
control cable slack, drive chain slack
and for loose spokes.
Notes on en gine overhauls
If the following parts have been re-
placed, they must be broken in as fol-
lows.  Piston, rings or transmission
gears: 30 minutes of break-in op-
eration at half-throttle or less.
 Cylinder or crankshaft: 60 minutes
of break-in operation is necessary.
TIP
Observe the condition of the engine
carefully during break-in operation.
NOTICE
ECA10271
If any en gine trou ble shoul d occur
d urin g the en gine break-in perio d,
imme diately have a Yamaha dealer
check the vehicle.
UBR882E0.book Page 2 Wednesd ay, February 26, 2020 11:39 AM

Periodic maintenance an d a djustment
7-2
7
EAU84193
Perio dic maintenance an d lu brication chart
The following chart is intended as a general guide to maintenance and lubrication.
Bear in mind that such factors as weather, terrain, geographical location, and in-
dividual usage will alter the required maintenance and lubrication intervals. If you
are in doubt as to what intervals to follow in maintaining and lubricating your mo-
torcycle, consult your Yamaha dealer.
TIP
Items marked with an asterisk should be performed by a Yamaha dealer as they
require special tools, data and technical skills.
NO. ITEM ROUTINEAfter
break-in
Everyrace
Every
third race
Every
fifth race
As
required
1 *Piston Check piston for carbon deposits and
cracks or damage. Clean.
Replace.

2 *
Piston rings Check piston ring end gap and rings
for damage.
Replace.
3 *
Piston pin and small
end bearing Check piston pin and small end
bearing for damage.
Replace.
4 *
Cylinder head Check cylinder head for carbon
deposits.
 Clean.
Check cylinder head gasket fordamage.
 Tighten cylinder head bolts ifnecessary.
Replace cylinder head gasket.

5 *
Cylinder
6*YPVS Check cylinder for score marks or
wear.


 Clean.
Replace.
Check YPVS for carbon deposits andcracks or damage.
Clean.

UBR882E0.book Page 2 Wednesd ay, February 26, 2020 11:39 AM

Periodic maintenance an d a djustment
7-11
7
5. Apply YAMALUBE foam air filter
oil to the entire surface of the
sponge material, and then
squeeze out the excess oil.
TIP
The sponge material should be
wet but not dripping.
 If YAMALUBE foam air filter oil is
not available in your area, another
high-quality foam air filter oil may
be used instead.
6. Pull the sponge material over the
air filter element frame.
7. Insert the air filter element into the air filter case by aligning the pro-
jection on the element with the slot
in the case, and then install the
wing bolt and its washer.
NOTICE: Make sure that the air
filter element is properly seated
in the air filter case. The en gine
shoul d never b e operated with-
out the air filter element in-
stalle d, otherwise the piston(s)
an d/or cylin der(s) may become
excessively worn.
[ECA10482]
NOTICE: Be sure to install the
washer with its curve d si de fac-
in g outwar d as shown.
[ECA16692]
8. Install the seat.
1. Slot
2. Projection
1. Washer
1 2
1
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