spark plugs replace YAMAHA MT-03 2018 Owners Manual

Periodic maintenance an d a djustment
6-7
6
EAU19643
Checkin g the spark plu gs
The spark plugs are important engine
components, which should be
checked periodically, preferably by a
Yamaha dealer. Since heat and depos- its will cause any spark plug to slowly
erode, they should be removed and
checked in accordance with the peri-
odic maintenance and lubrication
chart. In addition, the condition of the
spark plugs can reveal the condition of
the engine.
The porcelain insulator around the
center electrode of each spark plug
should be a medium-to-light tan (the
ideal color when the vehicle is ridden
normally), and all spark plugs installed
in the engine should have the same
color. If any spark plug shows a dis-
tinctly different color, the engine could
be operating improperly. Do not at-
tempt to diagnose such problems
yourself. Instead, have a Yamaha deal-
er check the vehicle.
If a spark plug shows signs of elec-
trode erosion and excessive carbon or
other deposits, it should be replaced.
Before installing a spark plug, the
spark plug gap should be measured
with a wire thickness gauge and, if
necessary, adjusted to specification. Clean the surface of the spark plug
gasket and its mating surface, and
then wipe off any grime from the spark
plug threads.
TIP
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.
Specified
spark plu g:
NGK/LMAR8A-9
1. Spark plug gap
Spark plu g g ap:
0.8–0.9 mm (0.031–0.035 in)
Ti ghtenin g torque:
Spark plug: 13 N·m (1.3 kgf·m, 9.6 lb·ft)
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Periodic maintenance an d a djustment
6-37
6
EAU63470
Trou bleshootin g charts
Startin g pro blems or poor en gine performance
1. FuelThere is enough fuel.
There is no fuel.
Check the battery.
Supply fuel.
The engine turns over
quickly.
The engine turns over
slowly.
The engine does not
start.
Check the battery.
Wipe off with a dry
cloth and correct the
spark plug gaps, or
replace the spark
plugs.
Check the battery
lead connections, and
have a Yamaha dealer
charge the battery if
necessary.
2. BatteryThe battery is good.
The engine does not
start.
Check the ignition.
3. IgnitionWetOperate the electric
starter.
Dry
There is compression.
There is no
compression.
The engine does not start.
Have a Yamaha dealer check the vehicle.
Have a Yamaha dealer check the vehicle.
The engine does not
start.
Check the
compression.Have a Yamaha
dealer check the
vehicle.
Remove the spark
plugs and check
the electrodes.
Operate the electric
starter.
Operate the electric
starter.
Check the fuel level
in the fuel tank.
4. Compression
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