Adjustments for Competition 133
Tuning Tips
An optional PGM-FI setting tool can change the
ignition timing and amount of the fuel injection
(page 157).
Be sure to observe the PGM-FI setting by
checking the spark plug.
Spark Plug Reading
Refer to Spark Plug on page 67.
The following procedure is recommended. You
may not get an accurate reading if you simply
turn off the engine and pull the plug for
inspection.
Use a new spark plug. Inspect the plug before
installing it.
Using spark plugs with an improper heat range
or incorrect reach can cause engine damage.
Ride for 10 – 15 minutes before taking a plug
reading. A new plug will not color immediately.
Before removing the spark plug, clean the spark
plug area thoroughly to prevent dirt from
entering the cylinder.
To obtain an accurate reading of a new spark
plug:
1. Accelerate at full throttle on a straight.
2. Depress and hold the engine stop button and
pull the clutch lever in.
3. Coast to a stop.
4. Remove the spark plug.
5. Use a magnifying glass to inspect the spark
plug. The porcelain insulator (1) around the
center electrode (2) should appear clean and
colorless with a gray ring around the center
electrode where it exits the porcelain.
Light gray or white color streaks the porcelain
insulator and center electrode indicate lean
air-fuel mixture. Wet or black sooty streaks
on the porcelain indicate rich air-fuel mixture.
NOTICE
Condition
Normal
Overheating
(Lean)
Wet
(Rich)
Spark Plug Appearance
Dark brown to light tan
color with dry electrode
Light gray or white color
Wet or sooty
Mixture
correct
lean
rich
An improperly tightened spark plug can damage
the engine. If a plug is too loose, a piston may
be damaged. If a plug is too tight, the threads
may be damaged.
NOTICE
(1) porcelain insulator (3) side electrode
(2) center electrode
Spark Plug Coloring Guidelines
Remember that in addition to improper air-fuel
mixture:
• A lean condition can be caused by air leaks in
the inlet tract or exhaust system, the passage
of too much air because of the use of the
wrong air cleaner, use of a less-restrictive
aftermarket exhaust system.
• A rich condition can be caused by a plugged
or dirty air cleaner, use of a more-restrictive
aftermarket exhaust system, or excessive oil
on the air cleaner.
Excessive smoking will occur.
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