2020 YAMAHA YFZ50 Starter

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EBU20292Starting a warm engineFollow the same procedure as for starting a cold
engine, with the exception that the starter (choke)
is not required when the engine is warm. Instead,
start the engine with the throttle slightly open.EBU36861Engine break-inThere is never a more important period in the life
of your engine than the first 240 km (150 mi) or 20
hours of operation. For this reason, you should fol-
low the engine break-in instructions carefully.
Since the engine is brand new, do not put an ex-
cessive load on it for the first 240 km (150 mi) or
20 hours. During this period the various parts in
the engine wear and polish themselves to the cor-
rect operating clearances. Avoid prolonged full-
throttle operation or any condition that might re-
sult in engine overheating.
0–120 km (0–75 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.120–240 km (75–150 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.
240 km (150 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. EBU36370ParkingWhen parking the ATV, apply the rear brake lever,
stop the engine, apply the parking brake, and then
turn the fuel cock to “OFF”.
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EBU36872Periodic 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 distance 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) 240
(150) 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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EBU25812Troubleshooting chart
Check the fuel level in
the fuel tank.1. Fuel
There is enough fuel.There is no fuel.
Check the battery.
Supply fuel.
The engine does not start.
Check the battery.
The engine does not start.
Check the ignition.
Operate the electric starter.4. Compression
There is compression.
There is no compression.
The engine does not start. Have a Yamaha dealer check the ATV.Have a Yamaha dealer check the ATV.
Remove the spark plug
and check the electrodes.3. Ignition
Wipe off with a dry cloth and correct the
spark plug gap, or replace the spark plug.
Have a Yamaha dealer check the ATV.
The engine does not start.
Check the compression.
Operate the electric starter.2. Battery
The engine turns over
quickly.
The engine turns over
slowly.
The battery is good.Check the battery lead connections.
Recharge the battery or use the
kickstarter.
DryWet
Open the throttle halfway and try
starting the engine.
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abrasives which may mar the paint or protec-
tive finish. When finished cleaning, start the
engine and let it idle for several minutes.
EBU30362StorageShort-term
Always store your ATV in a cool, dry place and, if
necessary, protect it against dust with a porous
cover.
NOTICE: Storing the ATV in a poorly ven-
tilated room or covering it with a tarp while it is
still wet, will allow water and humidity to seep
in and cause rust. To prevent corrosion, avoid
damp cellars, stables (because of the presence
of ammonia) and areas where strong chemi-
cals are stored.
[ECB00722]
Long-term
Before storing your ATV for several months: 1. Make any necessary repairs and perform all outstanding maintenance.
2. Follow all the instructions in the Cleaning sec- tion of this chapter. 3. Fill up the fuel tank and add fuel stabilizer (Fu-
el Med Rx if available), and then run the en-
gine for 5 minutes to distribute the treated
fuel.
4. Turn the fuel cock lever off, and then drain the carburetor float chamber by loosening the
drain bolt. Pour the drained fuel into the fuel
tank.
5. Perform the following steps to protect the en- gine from internal corrosion.a. Remove the spark plug cap and spark plug.
b. Pour a teaspoonful of engine oil into the spark plug bore.
c. Install the spark plug cap onto the spark plug, and then place the spark plug on the
cylinder head so that the electrodes are
grounded. (This will limit sparking during
the next step.)
d. Turn the engine over several times with the starter. (This will coat the cylinder wall
with oil.)
Specified amount:
7.5 ml per liter of fuel (1 oz per gallon)UBW463E0.book Page 2 Monday, January 28, 2019 10:22 AM

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EBU25963
SPECIFICATIONS
Dimensions:Overall length:1250 mm (49.2 in)
Overall width: 820 mm (32.3 in)
Overall height:
770 mm (30.3 in)
Seat height: 585 mm (23.0 in)
Wheelbase: 830 mm (32.7 in)
Ground clearance:
125 mm (4.9 in)
Minimum turning radius: 2.3 m (7.55 ft)
Maximum water depth: 11 cm (4 in)Weight:Curb weight:100.0 kg (220 lb)Loading:Maximum loading limit:
41.0 kg (90 lb)
(Total weight of rider, cargo, accessories, and tongue)Noise and vibration level:Noise level (77/311/EEC):74.0 dB(A) at 3625 r/min Uncertainty of measurement:
0.3 dB(A)
Vibration on seat (EN1032, ISO5008): Will not exceed 0.5 m/s²
Uncertainty of measurement: 0.1 m/s²
Vibration on handle (EN1032, ISO5008):
4.6 m/s²
Uncertainty of measurement: 0.4 m/s²
Engine:Combustion cycle:
4-stroke
Cooling system: Air cooled
Valve train: SOHC
Number of cylinders:
Single cylinder
Displacement: 49 cm³
Bore × stroke:
39.0 × 41.4 mm (1.54 × 1.63 in)
Compression ratio:
8.5 : 1
Starting system: Electric starter and kickstarter
Lubrication system: Wet sump
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INDEX
AAccessories and loading ................................................ 6-5
Air filter element, cleaning ........................................... 8-16BBattery ......................................................................... 8-32
Brake lever free play, adjusting the front ..................... 8-24
Brake lever free play (rear), adjusting .......................... 8-26
Brake lever, front ........................................................... 4-5
Brake lever, rear ............................................................. 4-6
Brake levers, checking and lubricating ........................ 8-30
Brakes .......................................................................... 8-22
Brakes, front and rear .................................................... 5-3CCables, checking and lubricating ................................ 8-29
Carburetor, adjusting ................................................... 8-20
Chassis fasteners .......................................................... 5-6
Cleaning ......................................................................... 9-1DDrive chain ..................................................................... 5-3
Drive chain, cleaning and lubricating ........................... 8-29
Drive chain slack .......................................................... 8-26EEngine break-in .............................................................. 6-3
Engine, cold start ........................................................... 6-1
Engine idling speed ..................................................... 8-20
Engine oil ..............................................................5-3, 8-11
Engine, starting a warm ................................................. 6-3
Engine stop switch ........................................................ 4-1
Engine stop switch with lanyard .................................... 4-2
FFront and rear brake shoes, checking ......................... 8-23
Front arm pivots, lubricating ........................................ 8-31
Front knuckle pivots, lubricating ................................. 8-31
Fuel ......................................................................... 4-9, 5-3
Fuel cock ..................................................................... 4-10
Fuel tank cap ................................................................. 4-8
Fuse, replacing ............................................................ 8-35HHandlebar switches ....................................................... 4-1IIdentification numbers ................................................. 11-1
Instruments and switches .............................................. 5-6KKickstarter ...................................................................... 4-7LLabel locations ............................................................... 1-1MMain switch .................................................................... 4-1
Maintenance and lubrication chart ................................ 8-5
Maintenance chart, emission control system ................ 8-3
Model label .................................................................. 11-1OOwner’s Manual and tool kit .......................................... 8-2PPanel, removing and installing ....................................... 8-9
Parking ........................................................................... 6-3
Parking brake ................................................................. 4-6
Parking on a slope ......................................................... 6-4
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Part locations ................................................................. 3-1RRiding your ATV ............................................................. 7-1SSafety information .......................................................... 2-1
Seat .............................................................................. 4-13
Shock absorber, rear ...................................................4-13
Spark arrester, cleaning ............................................... 8-19
Spark plug, checking .....................................................8-9
Specifications ............................................................... 10-1
Speed limiter .................................................................. 4-3
Starter (choke) .............................................................. 4-12
Start switch .................................................................... 4-2
Steering shaft, lubricating ............................................ 8-32
Storage ........................................................................... 9-2TThrottle lever .......................................................... 4-3, 5-3
Throttle lever free play, adjusting ................................. 8-22
Tires ............................................................................... 5-3
Transmission oil ................................................... 5-3, 8-15
Troubleshooting ........................................................... 8-37
Troubleshooting chart .................................................. 8-38VValve clearance ............................................................ 8-22
Vehicle identification number ....................................... 11-1WWheel hub bearings, checking ..................................... 8-30
Wheel, installing ........................................................... 8-36
Wheel, removing .......................................................... 8-36YYamalube ..................................................................... 8-14UBW463E0.book Page 2 Monday, January 28, 2019 10:22 AM