engine YAMAHA YFM350R 2008 Service Manual

8-20
8described in the following section, however, may
be performed by the owner as part of routine main-
tenance.
CAUTION:ECB00480The 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 ordamage to the engine.EBU24000Adjusting the engine idling speed The engine idling speed must be checked and, if
necessary, adjusted as follows at the intervals
specified in the periodic maintenance and lubrica-
tion chart.NOTE:A diagnostic tachometer is needed to make thisadjustment.
1. Start the engine and warm it up.NOTE:The engine is warm when it quickly responds to thethrottle.
2. Attach the tachometer to the spark plug lead.3. Check the engine idling speed and, if neces-
sary, adjust it to specification by turning the
throttle stop screw at the carburetor. To in-
crease the engine idling speed, turn the throt-
tle stop screw in direction (a), and to decrease
it, turn the screw in direction (b).
NOTE:If the specified idling speed cannot be obtained as
described above, have a Yamaha dealer make theadjustment.1. Throttle stop screwEngine idling speed:
1450–1550 r/min
U5YT64E0.book Page 20 Monday, April 9, 2007 1:03 PM

8-21
8
EBU24043Adjusting the throttle cable free play The throttle cable free play should be checked
and, if necessary, adjusted at the intervals speci-
fied in the periodic maintenance and lubrication
chart.
The throttle cable free play should measure 2.0–
4.0 mm (0.08–0.16 in) at the throttle lever. Period-
ically check the throttle cable free play and, if nec-
essary, adjust it as follows.NOTE:The engine idling speed must be checked, and ad-
justed if necessary, before adjusting the throttle ca-ble free play.
1. Loosen the locknut.
2. To increase the throttle cable free play, turn
the adjusting bolt in direction (a). To decrease
the throttle cable free play, turn the adjusting
bolt in direction (b).3. Tighten the locknut.
EBU24060Valve clearance The valve clearance changes with use, resulting in
improper air-fuel mixture and/or engine noise. To
prevent this from occurring, the valve clearance
must be adjusted by a Yamaha dealer at the inter-
vals specified in the periodic maintenance and lu-
brication chart.1. Locknut
2. Throttle cable free play adjusting bolt
3. Throttle cable free play
U5YT64E0.book Page 21 Monday, April 9, 2007 1:03 PM

8-32
8
CAUTION:ECB00560The drive chain must be lubricated after wash-ing the ATV or riding in the rain.
1. Clean the drive chain with kerosene and a
small soft brush.CAUTION:ECB00570To prevent damaging the O-rings, do not clean
the drive chain with steam cleaners, high-pres-sure washers or inappropriate solvents.
2. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a
special O-ring chain lubricant.
CAUTION:ECB00580Do not use engine oil or any other lubricants
for the drive chain, as they may contain sub-stances that could damage the O-rings.EBU24900Checking and lubricating the cables The operation and the condition of all control ca-
bles should be checked before each ride, and the
cables and cable ends should be lubricated if nec-
essary. If a cable is damaged or does not move
smoothly, have a Yamaha dealer check or replace
it.
WARNING
EWB02130Inspect cables frequently and replace if dam-
aged. Corrosion can result when the cable
sheaths become damaged, and cables can
also become frayed or kinked, which could re-
strict the operation of controls and lead to anaccident or injury.
1. O-ring
Recommended lubricant:
Engine oil
U5YT64E0.book Page 32 Monday, April 9, 2007 1:03 PM

8-44
8
EBU25751Troubleshooting chart
Check the fuel level in
the fuel tank.1. Fuel
There is enough fuel.
There is no fuel.
Check the compression.
Supply fuel.
The engine does not start.
Check the compression.
Operate the electric starter.2. Compression
There is compression.
There is no compression.
Check the ignition.
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.
Have a Yamaha dealer
check the ATV.
The engine does not start.
Check the battery.
Operate the electric starter.4. Battery
The engine turns over
quickly.
The engine turns over
slowly.
The battery is good.Check the battery lead connections,
and charge the battery if necessary.
DryWet
Open the throttle halfway and operate
the electric starter.
U5YT64E0.book Page 44 Monday, April 9, 2007 1:03 PM

9-1
9
EBU25860
CLEANING AND STORAGE
EBU25900Cleaning Frequent, thorough cleaning of your ATV will not
only enhance its appearance but will improve its
general performance and extend the useful life of
many components.
1. Before cleaning the ATV:
a. Block off the end of the exhaust pipe to
prevent water entry. A plastic bag and
strong rubber band may be used.
b. Make sure the spark plug and all filler caps
are properly installed.
2. If the engine case is excessively greasy, apply
degreaser with a paint brush. Do not apply de-
greaser to the chain, sprockets or wheel ax-
les.
3. Rinse the dirt and degreaser off with a garden
hose. Use only enough pressure to do the job.CAUTION:ECB00710Excessive water pressure may cause water
seepage and deterioration of wheel bearings,
brakes, transmission seals and electrical de-
vices. Many expensive repair bills have result-ed from improper high-pressure detergent
applications such as those available in coin-
operated car washers.
4. Once most of the dirt has been hosed off,
wash all surfaces with warm water and mild,
detergent-type soap. An old toothbrush or bot-
tle brush is handy for hard-to-reach places.
5. Rinse the ATV off immediately with clean wa-
ter and dry all surfaces with a chamois, clean
towel or soft absorbing cloth.
6. Dry the chain and lubricate it to prevent it from
rusting.
7. Clean the seat with a vinyl upholstery cleaner
to keep the cover pliable and glossy.
8. Automotive type wax may be applied to all
painted and chrome plated surfaces. Avoid
combination cleaner-waxes. Many contain
abrasives which may mar the paint or protec-
tive finish. When finished cleaning, start the
engine and let it idle for several minutes.
U5YT64E0.book Page 1 Monday, April 9, 2007 1:03 PM

9-2
9
WARNING
EWB02310Wet brakes may have reduced stopping ability,
increasing the chance of an accident. Test the
brakes after washing. Apply the brakes several
times at slow speeds to let friction dry out thelinings.EBU25932Storage Short-term
Always store your ATV in a cool, dry place and, if
necessary, protect it against dust with a porous
cover.CAUTION:ECB00720
Storing the ATV in a poorly ventilated 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 ammo-
nia) and areas where strong chemicals arestored.Long-term
Before storing your ATV for several months:
1. Follow all the instructions in the “Cleaning”
section of this chapter.
2. Turn the fuel cock lever to “OFF”.
3. Drain the carburetor float chamber by loosen-
ing the drain bolt; this will prevent fuel deposits
from building up. Pour the drained fuel into the
fuel tank.
4. Fill up the fuel tank and add fuel stabilizer (if
available) to prevent the fuel from deteriorat-
ing.
5. Perform the following steps to protect the cyl-
inder, piston rings, etc. from corrosion.
a. Remove the spark plug cap and spark
plug.
b. Pour a teaspoonful of engine oil into the
spark plug bore. Specified amount:
7.5 ml of stabilizer to each liter of fuel (or 1 oz
of stabilizer to each gallon of fuel)
U5YT64E0.book Page 2 Monday, April 9, 2007 1:03 PM

9-3
9 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.)
e. Remove the spark plug cap from the spark
plug, and then install the spark plug and
the spark plug cap.
6. Lubricate all control cables and the pivoting
points of all levers and pedals.
7. Check and, if necessary, correct the tire air
pressure, and then block up the ATV so that
all of its wheels are off the ground. Alternative-
ly, turn the wheels a little every month in order
to prevent the tires from becoming degraded
in one spot.
8. Cover the muffler outlet with a plastic bag to
prevent moisture from entering it.
9. Remove the battery and fully charge it. Store
it in a cool, dry place and charge it once a
month. Do not store the battery in an exces-
sively cold or warm place [less than 0 °C (30°F) or more than 30 °C (90 °F)]. For more in-
formation on storing the battery, see page
8-37.
NOTE:Make any necessary repairs before storing theATV.
U5YT64E0.book Page 3 Monday, April 9, 2007 1:03 PM

10-1
10
EBU25960
SPECIFICATIONS
Dimensions:Overall length:
1780 mm (70.1 in)
Overall width:
1095 mm (43.1 in)
Overall height:
1080 mm (42.5 in)
Seat height:
820 mm (32.3 in)
Wheelbase:
1210 mm (47.6 in)
Ground clearance:
115 mm (4.5 in)
Minimum turning radius:
3100 mm (122 in)Weight:With oil and fuel:
180.0 kg (397 lb)Engine:Engine type:
Air cooled 4-stroke, SOHC
Cylinder arrangement:
Forward-inclined single cylinder
Displacement:
349.0 cm³
Bore × stroke:
83.0 × 64.5 mm (3.27 × 2.54 in)Compression ratio:
9.20 :1
Starting system:
Electric starter
Lubrication system:
Wet sump
Engine oil:Type:
SAE5W30 or SAE10W30 or SAE10W40 or SAE15W40
or SAE20W40 or SAE20W50
Recommended engine oil grade:
API service SG type or higher, JASO standard MA-20˚ -10˚ 0˚
10˚20˚ 30˚40˚50˚C
10W/30
15W/4020W/4020W/50
10W/40
5W/30
U5YT64E0.book Page 1 Monday, April 9, 2007 1:03 PM

10-2
10
Engine oil quantity:
Without oil filter element replacement:
2.50 L (2.64 US qt) (2.20 Imp.qt)
With oil filter element replacement:
2.60 L (2.75 US qt) (2.29 Imp.qt)Air filter:Air filter element:
Wet elementFuel:Recommended fuel:
Regular unleaded gasoline only (EUR)
Unleaded gasoline only (AUS)(NZL)
Fuel tank capacity:
9.0 L (2.38 US gal) (1.98 Imp.gal)
Fuel reserve amount:
2.7 L (0.71 US gal) (0.59 Imp.gal)Carburetor:Manufacturer:
MIKUNI
Type x quantity:
BSR36 x 1Spark plug (s):Manufacturer/model:
NGK/DR8EA
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)Clutch:Clutch type:
Wet, multiple-disc
Operation:
Left hand operation
Transmission:Primary reduction system:
Spur gear
Primary reduction ratio:
76/24 (3.166)
Secondary reduction system:
Chain drive
Secondary reduction ratio:
38/13 (2.923)
Transmission type:
Constant mesh 6-speed.forward, 1-speed.reverse
Operation:
Left foot operation
Gear ratio:
1st:
36/16 × 20/27 × 29/18 (2.685)
2nd:
33/20 × 20/27 × 29/18 (1.969)
3rd:
29/23 × 20/27 × 29/18 (1.504)
4th:
27/26 × 20/27 × 29/18 (1.239)
5th:
25/28 × 20/27 × 29/18 (1.065)
6th:
23/29 × 20/27 × 29/18 (0.946)
Reverse gear:
33/16 × 33/10 (6.806)Chassis:Frame type:
Steel tube frame
U5YT64E0.book Page 2 Monday, April 9, 2007 1:03 PM

INDEX
AAccessories and loading ................................................ 6-8
Air filter element, cleaning ............................................ 8-14BBattery .......................................................................... 8-37
Brake and clutch levers, checking and lubricating ....... 8-33
Brake and shift pedals, checking and lubricating ......... 8-33
Brake fluid, changing .................................................... 8-24
Brake fluid level, checking ............................................ 8-23
Brake lever ..................................................................... 4-5
Brake lever free play, checking the front ...................... 8-24
Brake light switches ..................................................... 8-27
Brake pads, checking the front and rear ...................... 8-22
Brake pedal .................................................................... 4-5
Brake pedal position, checking .................................... 8-25
Brakes, front and rear .................................................... 5-3CCables, checking and lubricating ................................. 8-32
Carburetor, adjusting .................................................... 8-19
Chassis fasteners ........................................................... 5-7
Cleaning ......................................................................... 9-1
Clutch lever .................................................................... 4-5
Clutch lever free play, adjusting ................................... 8-28DDrive chain ..................................................................... 5-4
Drive chain, lubricating ................................................. 8-31
Drive chain slack .......................................................... 8-29
Drive select lever ............................................................ 4-7Drive select lever and driving in reverse ........................ 6-3
EEngine break-in .............................................................. 6-6
Engine, cold start ........................................................... 6-1
Engine idling speed ...................................................... 8-20
Engine oil ....................................................................... 5-3
Engine oil and oil filter element .................................... 8-11
Engine, starting a warm ................................................. 6-3
Engine stop switch ......................................................... 4-2FFuel ......................................................................... 4-8, 5-3
Fuel cock ........................................................................ 4-9
Fuel tank cap .................................................................. 4-8
Fuse, replacing ............................................................. 8-38HHandlebar switches ........................................................ 4-2
Headlight beam, adjusting ............................................ 8-41
Headlight bulb, replacing .............................................. 8-39IIdentification numbers .................................................. 11-1
Indicator lights ................................................................ 4-2
Instruments, lights and switches .................................... 5-7KKey identification number ............................................. 11-1LLabel locations ............................................................... 2-1
Light switch .................................................................... 4-3
U5YT64E0.book Page 1 Monday, April 9, 2007 1:03 PM