Spark Plugs - Buell 2007 LIGHTNING Service Manual

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SPARK PLUGS

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 2.39 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 2.44
5. Remove air cleaner assembly. See
ASSEMBLY/ 4.44 AIR CLEANER
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 1-37. 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.
SEAT.
2.38 INTAKE COVER
ASSEMBLY.
4636
Figure 1-37. Typical Spark Plug Deposits
2007 Buell Lightning: Maintenance
1.13
1-39