2004 YAMAHA YFM50S fuel

6-3
EBU14410
Starting a cold engine
w
Always make sure all control cables work
smoothly before you begin riding in cold
weather. If the control cables are froze or do
not work smoothly, you could be unable to
control the ATV, which could lead to an acci-
dent or collision.
1. Set the parking brake.
2. Turn the fuel cock to “ON”.
3. Turn the main switch to “ON” and the
engine stop switch to “RUN”.
4. Shift the transmission into neutral.
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6-23
EBU00211
Parking
When parking, stop the engine and shift into
neutral. Turn the fuel cock to “OFF” and apply
the parking brake.q
1
1. Lock plate1. Plaque de verrouillage1. Placa de bloqueo
1. Locked position
1. Verrouillé1. Posición bloqueada
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8-7
EBU00262
PERIODIC MAINTENANCE/LUBRICATION
INITIAL EVERY
ITEM ROUTINE 1 3 6 6 1
month months months months year
Valves*9Check valve clearance.
9Adjust if necessary.2 222
Cam chain*9Check chain tension.
9Adjust if necessary.2 222
9Check condition.
Spark plug9Adjust gap and clean.22222
9Replace if necessary.
Air filter element9Clean. Every 20–40 hours.
9Replace if necessary. (more often in wet or dusty areas)
Carburetor*9Check idle speed/choke lever operation.
2222
9Adjust if necessary.
Crankcase breather9Check breather hose for cracks or damage.
system*9Replace if necessary.222
9Check for leakage.
Exhaust system*9Tighten if necessary.222
9Replace gasket if necessary.
Fuel line*9Check fuel hose for cracks or damage.
222
9Replace if necessary.
Engine oil9Replace (warm engine before draining).2 222
Final gear oil9Check oil level/oil leakage.
22
9Replace every 12 months.
Brakes*9Check operation.
22222
9Adjust if necessary.
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8-39
EBU00303
Valve clearance adjustment
The correct valve clearance changes with use,
resulting in improper fuel/air supply or engine
noise. To prevent this, the valve clearance must
be adjusted regularly. This adjustment however,
should be left to a professional Yamaha service
technician.
EBU00304
Cam chain adjustment
The cam chain becomes loose with use, result-
ing in improper valve timing and engine noise.
To prevent this, the cam chain tensioner must
be adjusted regularly. This adjustment should be
left to a Yamaha service technician.
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8-67
EBU00413
Troubleshooting
Although Yamaha machines receive a rigid
inspection before shipment from the factory,
trouble may occur during operation.
Any problem in the fuel, compression, or ignition
systems can cause poor starting and loss of
power. The troubleshooting chart describes a
quick, easy procedure for making checks. If
your machine requires any repair, take it to a
Yamaha dealer.
The skilled technicians at a Yamaha dealership
have the tools, experience, and know-how to
properly service your machine. Use only gen-
uine Yamaha parts on your machine. Imitation
parts may look like Yamaha parts, but they are
often inferior. Consequently, they have a short-
er service life and can lead to expensive repair
bills.
5YF-9-60 8 4/24/03 6:35 PM Page 8-67

w
Do not smoke when checking the fuel sys-
tem. Fuel can ignite or explode, causing
severe injury or property damage. Make sure
there are no open flames or sparks in the
area, including pilot lights from water
heaters or furnaces.
8-69
5YF-9-60 8 4/24/03 6:35 PM Page 8-69

EBU00440
Troubleshooting chart
1. Fuel
Check if there is
fuel in the fuel
tank
2. Compression
Use electric starter
to see if there is
compression
3. Ignition
Remove spark plug
and check electrodes
WetWipe clean with dry
cloth
DryAttach spark plug cap
and ground to chassisUse electric
starterSpark weak
Spark goodIgnition system normal
No spark
Ask a Yamaha dealer to inspect
Adjust spark plug gap
or replace spark plug
There is compressonCompression normal
Ask a Yamaha dealer to inspectNo compression
There is fuelTurn the fuel
cock to “OFF”
Remove the
fuel hose from
the fuel cock.
Some fuelTurn the fuel
cock to “RES”Restart engine
No fuelSupply fuel
4. Battery
Use electric
starter
Engine turns
over quicklyBattery good
Engine turns
over slowlyCheck fluid, recharge,
check connections
Check fuel flow
Water or dirt
mixed in fuel
Turn the fuel
cock to “ON”No fuelFuel cock clogged
Clean the fuel filter
and the fuel tank
Clean fuel cock
8-71
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9-7
EBU00427
B. STORAGE
Long term storage (60 days or more) of your
machine will require some preventive proce-
dures to guard against deterioration. After thor-
oughly cleaning the machine, prepare for stor-
age as follows:
1. Fill the fuel tank with fresh fuel and add
fuel stabilizer (if available).
NOTE:
Use of fuel stabilizer eliminates the need to
drain the fuel system. Consult a Yamaha dealer
if the fuel system is to be drained instead.
2. Remove the spark plug, pour about one
tablespoon of SAE 10W30 or 20W40
motor oil in the spark plug hole and rein-
stall the spark plug. Ground the spark plug
wire and turn the engine over several times
to coat the cylinder wall with oil.
3. Lubricate all control cables.
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