1-36 2003 Buell XB9S: Maintenance
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SPARK PLUGS 1.14
INSPECTION
Check spark plugs:
●
Inspect at every 5000 mile (8000 km) service interval.
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Replace every 10,000 mile (16,000 km) service interval.
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Use only Harley-Davidson 10R12A spark plugs (Part No.
27671-01K).
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 4.43 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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