maintenance YAMAHA YFM50R 2007 User Guide

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EBU23211
Checking the spark plug
The spark plug is an important engine component,
which is easy to check. Since heat and deposits
will cause any spark plug to slowly erode, the spark
plug should be removed and checked in accor-
dance with the periodic maintenance and lubrica-
tion chart. In addition, the condition of the spark
plug can reveal the condition of the engine.
To remove the spark plug
1. Remove the spark plug cap.
2. Remove the spark plug as shown, with thespark plug wrench included in the owner’s tool
kit.
To check the spark plug
1. Check that the porcelain insulator around the
center electrode of the spark plug is a medi-
um-to-light tan (the ideal color when the ATV
is ridden normally).
NOTE:

If the spark plug shows a distinctly different color,
the engine could be operating improperly. Do not
attempt to diagnose such problems yourself. In-
stead, have a Yamaha dealer check the ATV.
1. Spark plug cap
1

1. Spark plug wrench
1

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2. Check the spark plug for electrode erosion
and excessive carbon or other deposits, and
replace it if necessary.
To install the spark plug
1. Measure the spark plug gap with a wire thick-
ness gauge and, if necessary, adjust the gap
to specification.2. Clean the surface of the spark plug gasket
and its mating surface, and then wipe off any
grime from the spark plug threads.
3. Install the spark plug with the spark plug
wrench, and then tighten it to the specified
torque.NOTE:

If a torque wrench is not available when installing
a 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 specified torque as
soon as possible.
4. Install the spark plug cap.
EBU23251
Engine oil
The engine oil level should be checked before
each ride. In addition, the oil must be changed at
the intervals specified in the periodic maintenance
and lubrication chart. Specified spark plug:
NGK/CR7HSA
Spark plug gap:
0.6–0.7 mm (0.024–0.028 in)
1. Spark plug gap
Tightening torque:
Spark plug:
12.5 Nm (1.25 m·kgf, 9.0 ft·lbf)

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minutes while checking it for oil leakage. If oil
is leaking, immediately turn the engine off and
check for the cause.
9. Turn the engine off, and then check the oil lev-
el and correct it if necessary.
EBU23403
Final gear oil
The final gear case must be checked for oil leak-
age before each ride. If any leakage is found, have
a Yamaha dealer check and repair the ATV. In ad-
dition, the final gear oil level must be checked and
the oil changed as follows at the intervals specified
in the periodic maintenance and lubrication chart.
To check the final gear oil level
1. Place the ATV on a level surface.
NOTE:

The final gear oil level must be checked on a cold
engine.
2. Remove the final gear oil filler cap, wipe the
dipstick off with a clean rag, insert it back into
the oil filler hole (without screwing it in), and
then remove it again to check the oil level.
NOTE:

The final gear oil should be between the minimum
and maximum level marks.
3. If the oil is at or below the minimum level mark,
add sufficient oil of the recommended type to
raise it to the correct level.
4. Insert the dipstick into the oil filler hole, and
then tighten the oil filler cap.
1. Final gear oil filler cap
2. Dipstick
3. Maximum level mark
4. Minimum level mark
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To change the final gear oil
1. Place the ATV on a level surface.
2. Place an oil pan under the final gear case to
collect the used oil.
3. Remove the final gear oil filler cap and the fi-
nal gear oil drain bolt to drain the oil from the
final gear case.
4. Install the drain bolt, and then tighten it to the
specified torque.5. Add the specified amount of the recommend-
ed final gear oil, and then check the oil level.CAUTION:
ECB00420
Be sure no foreign material enters the final
gear case.
6. Install and tighten the oil filler cap.
7. Check the final gear case for oil leakage. If oil
is leaking, check for the cause.
EBU23801
Cleaning the air filter element
The air filter element should be cleaned at the in-
tervals specified in the periodic maintenance and
lubrication chart. Clean the air filter element more
frequently if you are riding in unusually wet or dusty
areas.
NOTE:

There is a check hose at the bottom of the air filter
case. If dust or water collects in this hose, empty
1. Final gear oil drain bolt
Tightening torque:
Final gear oil drain bolt:
23 Nm (2.3 m·kgf, 16.6 ft·lbf)
1

Recommended final gear oil:
See page 10-1.
Oil quantity:
0.12 L (0.13 US qt) (0.11 Imp.qt)

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plode.
5. Squeeze the excess solvent out of the sponge
material and let it dry.
CAUTION:

ECB00440
Do not twist the sponge material when squeez-
ing it.
6. Check the sponge material and replace it if
damaged.
7. Apply a quality foam air filter oil to the sponge
material.
NOTE:

The sponge material should be wet but not drip-
ping.
8. Install the sponge material into the air filter el-
ement.
9. Place the air filter element in the original posi-
tion, and then hook the holder.
10. Install the air filter case cover by hooking the
holders onto the air filter case.
11. Install the panel by installing the bolts.
NOTE:

The air filter element should be cleaned every 20–
40 hours. It should be cleaned and lubricated moreoften if the ATV is operated in extremely dusty ar-
eas. Each time the air filter element maintenance
is performed, check the air inlet of the air filter case
for obstructions.
CAUTION:

ECB00460

Make sure that the air filter element is prop-
erly seated in the air filter case.

Never operate the engine with the air filter el-
ement removed. This will allow unfiltered air
to enter the engine, causing rapid engine
wear and possible engine damage. Addition-
ally, operation without the air filter element
will affect carburetor jetting with subsequent
poor performance and possible engine over-
heating.
EBU27630
Cleaning the spark arrester
Be sure the exhaust pipe and muffler are cool be-
fore cleaning the spark arrester.
1. Remove the screws.

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EBU23940
Adjusting the carburetor
The carburetor should be checked and, if neces-
sary, adjusted at the intervals specified in the peri-
odic maintenance and lubrication chart. The
carburetor is an important part of the engine and
requires very sophisticated adjustment. Therefore,
most carburetor adjustments should be left to a
Yamaha dealer, who has the necessary profes-
sional knowledge and experience. The adjustment
described in the following section, however, may
be performed by the owner as part of routine main-
tenance.
CAUTION:

ECB00480
The 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.
EBU24000
Adjusting 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 this
adjustment.
1. Start the engine and warm it up.
NOTE:

The engine is warm when it quickly responds to the
throttle.
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).

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NOTE:

If the specified idling speed cannot be obtained as
described above, have a Yamaha dealer make the
adjustment.
EBU27071
Checking the throttle cable free play
The throttle cable free play should be checked at
the intervals specified in the periodic maintenance
and lubrication chart.The throttle cable free play should measure 1.0–
3.0 mm (0.04–0.12 in) at the throttle lever. Period-
ically check the throttle cable free play and, if nec-
essary, have a Yamaha dealer adjust it.
EBU24060
Valve 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. Throttle stop screw
Engine idling speed:
1750–1850 r/min
1 (a) (b)

1. Throttle lever free play
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EBU24090
Checking the front and rear brake
shoes
The front and rear brake shoes must be checked
for wear at the intervals specified in the periodic
maintenance and lubrication chart. Each brake is
provided with a wear indicator, which allows you to
check the brake shoe wear without having to dis-
assemble the brake. To check the brake shoe
wear, check the position of the wear indicator while
applying the brake. If a brake shoe has worn to the
point that the wear indicator reaches the wear limit
line or mark, have a Yamaha dealer replace the
brake shoes as a set.
Front brake
1. Wear limit line
2. Wear indicator
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Rear brake

EBU24330
Adjusting the front brake lever free
play
The brake lever free play must be checked and, if
necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
NOTE:

Before adjusting the brake lever free play, check
the front brake shoes for wear.
The brake lever free play should measure 10.0–12.0 mm (0.39–0.47 in) as shown. If the free play
is incorrect, adjust it as follows.
1. Loosen the upper locknut and fully turn in the
upper adjusting bolt.
2. Loosen the lower locknut.
3. Turn the lower adjusting bolt in direction (a) to
increase the free play, and in direction (b) to
decrease it.
1. Wear limit mark
2. Wear indicator
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1. Brake lever free play
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should be performed by a Yamaha dealer.
EBU24451
Adjusting the rear brake lever free play
The brake lever free play must be checked and, if
necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
NOTE:

Before adjusting the brake lever free play, check
the rear brake shoes for wear.
The brake lever free play should measure 7.0–
10.0 mm (0.28–0.39 in) as shown. If the free play
is incorrect, adjust it as follows.
1. Loosen the locknut at the brake lever.
2. Turn the brake lever free play adjusting bolt at
the brake lever in direction (a) to increase the
free play, and in direction (b) to decrease it.
3. Tighten the locknut at the brake lever.
If the specified free play cannot be obtained,
proceed with the following steps.
4. Loosen the locknut at the brake lever.
5. Fully turn the adjusting bolt at the brake lever
in direction (a) to loosen the brake cable.
6. To increase the brake lever free play, turn the
1. Brake lever free play
2. Locknut
3. Brake lever free play adjusting bolt
312
(a)
(b)