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Tuning Tips
Tuning Tips
An optional PGM-FI setting tool can change the
ignition timing and amount of the fuel injection
(page 186).
Be sure to observe the PGM-FI setting by checking
the spark plug.
Spark Plug Reading
Refer to Spark Plug on page 82.
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.
158
Adjustments for Competition
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 colour 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
centre electrode (2) should appear clean and
colourless with a gray ring around the centre
electrode where it exits the porcelain.
Light gray or white colour streaks on the
porcelain insulator and centre electrode
indicate lean air-fuel mixture. Wet or black
sooty streaks on the porcelain indicate rich air-
fuel mixture.
An improperly tightened spark plug can damage
the engine. If a plug is too loose, the piston may be
damaged. If a plug is too tight, the threads may be
damaged.
(1) porcelain insulator
(2) centre electrode
Spark Plug Colouring Guidelines
Condition
Spark Plug Appearance
Normal
Dark brown to light tan
colour with dry electrode
Overheating
Light gray or white colour
(Lean)
Wet (Rich)
Wet or sooty
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, or 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.
(2)
(1)
Mixture
correct
lean
rich
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