Buell 2004 XB9S, Service Manual, Page: 85 / 597

1-36 2004 Buell Lightning: Maintenance
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SPARK PLUGS 1.14
INSPECTION
Check spark plugs:
● Replace every 10,000 mile (16,000 km) service interval.
●
Use only Harley-Davidson 10R12A spark plugs.
1. Remove left side air scoop to access front cylinder spark
plug. See 2.36 AIR SCOOPS .
2. Disconnect spark plug wire from front spark plug.
3. Using a 5/8 in. box end wrench and 5/8 in. spark plug
socket, remove front spark plug.
4. Remove seat. See 2.41 SEAT .
5. Remove airbox assembly. See 4.30 AIRBOX .
6. Disconnect spark plug wire from rear spark plug (use
automotive spark plug boot remover/installer if required).
7. Using a 5/8 in. wobble socket and 12 in. extension,
remove rear spark plug.
8. See Figure 1-35. Compare your observations of the plug
deposits with the descriptions provided below.
a. A wet, black and shiny deposit on plug base, elec-
trodes and ceramic insulator tip indicates an oil
fouled plug. The condition may be caused by one or
more of the following: worn pistons, worn piston
rings, worn valves, worn valve guides, worn valve
seals, a weak battery or a faulty ignition system.
b. A dry, fluffy or sooty black deposit indicates an air-
fuel mixture that is too rich and/or engine idling for
excessive periods.
c. A light brown, glassy deposit indicates an over-
heated plug. This condition may be accompanied by
cracks in the insulator or by erosion of the elec-
trodes and is caused by an air-fuel mixture that is
too lean, a hot-running engine, valves not seating or
improper ignition timing. The glassy deposit on the
spark plug is a conductor when hot and may cause
high-speed misfiring. A plug with eroded electrodes,
heavy deposits or a cracked insulator must be
replaced.
d. A plug with a white, yellow, tan or rusty brown pow-
dery deposit indicates balanced combustion. Clean
off spark plug deposits at regular intervals.
Figure 1-35. Typical Spark Plug Deposits
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