8-39
EBU00287
Spark plug inspection
The spark plugs are important engine compo-
nents and are easy to inspect. The condition of
the spark plugs can indicate the condition of the
engine.
Normally, all spark plugs from the same engine
should have the same color on the white porce-
lain insulator around the center electrode. The
ideal color at this point is a medium to light tan
color for a machine that is being ridden normal-
ly. If one spark plug shows a distinctly different
color, there could be something wrong with the
engine.
Do not attempt to diagnose such problems your-
self. Instead, take the machine to a Yamaha
dealer. You should periodically remove and
inspect the spark plugs because heat and
deposits will cause any spark plug to slowly
break down and erode. If electrode erosion
becomes excessive, or if carbon and other
deposits are excessive, you should replace the
spark plug with the specified plug.
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EBU00440
Troubleshooting chart
Starting problems or poor engine performance
Check fuel flow
1. Fuel
Check if there is
fuel in the fuel
tank
2. Compression
Kick the kick starter
to see if there is
compression
3. Ignition
Remove plugs and
check electrodes
WetWipe clean with
dry cloth
DryAttach plug cap and
ground to chassisKick the kick
starter stronglySpark weak
Spark goodIgnition system normal
No spark
Ask a Yamaha dealer to inspect
Adjust plug gap or
replace plug(s)
There is compressonCompression normal
Ask a Yamaha dealer to inspectNo compression
There is fuelTurn the fuel
cock to “OFF”
Remove the
fuel pipeNo fuelFuel cock clogged
Some fuelTurn the fuel
cock to “RES”Restart engine
No fuelSupply fuel
Clean fuel cock
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