engine YAMAHA YFM400F 2001 Workshop Manual

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8. Reinstall the element to the element
guide.
9. Reinstall the element assembly and parts
removed for access.NOTE:The air filter element should be cleaned every
20 ~ 40 hours. It should be cleaned and lubri-
cated more often if the machine is operated in
extremely dusty areas. Each time filter element
maintenance is performed, check the air inlet
to the filter case for obstructions. Check the air
cleaner rubber joint to the carburetor and man-
ifold fittings for an air-tight seal. Tighten all fit-
tings securely to avoid the possibility ofunfiltered air entering the engine.CAUTION:Never operate the engine with the air filter el-
ement removed. This will allow unfiltered air
to enter, causing rapid engine wear and possi-
ble engine damage. Additionally, operation
without the filter element will affect carbure-
tor jetting with subsequent poor performanceand possible engine overheating.
1. Connect the hose.
1. Brancher le flexible.
1. Conecte la manguera.

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Carburetor adjustment
The carburetor is a vital part of the engine and
requires very sophisticated adjustment. Most
adjusting should be left to a Yamaha dealer
who has the professional knowledge and expe-
rience to do so. However, the idling speed may
be performed by the owner as a part of the
usual maintenance routine.CAUTION:The carburetor was set at the Yamaha factory
after many tests. If the settings are disturbed
by someone without sufficient technical
knowledge, poor engine performance anddamage may result.

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Idle speed adjustmentNOTE:A diagnostic tachometer must be used for thisprocedure.
1. Start the engine and warm it up for a few
minutes at approximately 1,000 to
2,000 r/min. Occasionally rev the engine
to 4,000 to 5,000 r/min. The engine is
warm when it quickly responds to the
throttle.
2. Remove panel D. (See pages 8-17 ~ 8-21
for removal and installation procedures.)
3. Connect the tachometer and set the idle to
the specified idling speed by adjusting the
throttle stop screw. Turn the screw in to
increase engine speed, and out to de-
crease engine speed.
4. Install the panel.Specified idle speed:
1,450 ~ 1,550 r/min
1. Throttle stop screw
1. Vis d’arrêt de l’accélérateur
1. Tornillo de tope del acelerador

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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.

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Throttle lever adjustmentNOTE:Adjust the engine idling speed before adjust-ing the throttle lever free play.
1. Loosen the locknut.
2. Turn the adjusting bolt until the throttle le-
ver free play is 3 ~ 5 mm.
3. Tighten the locknut.
1. Locknut 2. Adjusting bolt
1. Contre-écrou 2. Bouchon de réglage
1. Contratuerca 2. Perno de ajustea. Free play
a. Jeu
a. Juego libre

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Cable inspection and lubrication
WARNING
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the outer
covering of control cables becomes damaged.
Cables can also become frayed or kinked. Op-
eration of controls could be restricted, whichcould cause an accident or injury.
Lubricate the inner cables and the cable ends.
If the cables do not operate smoothly, ask a
Yamaha dealer to replace them.
Recommended lubricant:
Engine oil

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EBU00724Troubleshooting chart
Starting problems or poor engine performance1. Fuel
Check if there is fuel
in the fuel tank.There is fuel.Turn the fuel cock
lever to “OFF”.No fuel.Fuel cock is
clogged.
Clean the
fuel cock. Some fuel.Turn the fuel cock
lever to “RES”.Restart the engine.
No fuel.Supply fuel.
2. Compression
Use the electric
starter to see if
there is compression.There is compression.
Compression normal.
No compression.Ask a Yamaha dealer to
inspect.
3. Ignition
Remove the
spark plug and
check electrodes.WetWipe clean with dry cloth.
DryAttach spark plug cap and
ground to chassis.Use the
electric starter.Spark is good.Ignition system is
normal.
Spark is weak.
Adjust the spark plug gap
or replace the spark plug. No spark.
Ask a Yamaha dealer to
inspect. 4. Battery
Use the electric starter.Engine turns over
quickly.Battery is good.
Engine turns over
slowly.Check the connections.Check the
fuel flow.
Turn the fuel cock
lever to “ON”.
Remove the fuel hose
from the fuel cock.

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Engine overheatingNOTE:If it is difficult to get the recommended coolant, tap water can be temporarily used, provided that itis changed to the recommended coolant as soon as possible.
WARNING
Wait for the engine and radiator to cool before removing the radiator cap. You could be burned by
hot fluid and steam blown out under pressure. Always put a thick rag over the cap when opening.Allow any remaining pressure to escape before completely removing the cap. Wait until the
engine has cooled.
Check the coolant level in the
reservoir tank and/or radiator.
Level is OK.Level is low, check the
cooling system for leakage.
No
leakage.Leakage.
Ask a Yamaha dealer to inspect
and repair the cooling system.Add coolant. (See NOTE.)
Restart the engine. If the engine overheats again, ask a
Yamaha dealer to inspect and/or repair the cooling system.

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CLEANING AND STORAGE
A. CLEANING
Frequent, thorough cleaning of your machine
will not only enhance its appearance but will
improve its general performance and extend
the useful life of many components.
1. Before cleaning the machine:
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 degreaser to the wheel axles.
3. Rinse the dirt and degreaser off with a
garden hose. Use only enough pressure
to do the job.

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7. 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 protective finish.
When finished, start the engine and let it
idle for several minutes.
WARNING

Wet brakes may have reduced stopping abili-
ty, increasing the chance of an accident. Test
the brakes after washing. Apply the brakes
several times at slow speeds to let friction dry
out the linings.