8-39
EBU00287Spark 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.
5FK-9-63-8 2/7/02 1:28 PM Page 40
8-117
EBU00440Troubleshooting chartStarting problems or poor engine performance
Check fuel flow
1. FuelCheck if there is
fuel in the fuel
tank2. CompressionKick the kick starter
to see if there is
compression3. IgnitionRemove plugs and
check electrodes
Wet
Wipe clean with
dry cloth
Dry
Attach plug cap and
ground to chassis
Kick the kick
starter strongly
Spark weakSpark good
Ignition system normal
No spark
Ask a Yamaha dealer to inspect
Adjust plug gap or
replace plug(s)
There is compresson
Compression normalAsk a Yamaha dealer to inspect
No compression
There is fuel
Turn the fuel
cock to “OFF”Remove the
fuel pipe
No fuel
Fuel cock clogged
Some fuel
Turn the fuel
cock to “RES”
Restart engine
No fuel
Supply fuel
Clean fuel cock
5FK-9-63-8 2/7/02 1:28 PM Page 118
