Honda 85RB EXPERT 2006, Owner'S Manual

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94
Adjustments for Competition
Carburetor Adjustments & Tuning Tips
Spark Plug Reading
Refer to Spark Plug on page 46.
Check any jetting change by reading the spark
plug. 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.
Before removing the spark plug, clean the spark
plug area thoroughly to prevent dirt from enter-
ing the cylinder.
Ride for 10 - 15 minutes before taking a plug
reading. A new plug will not color immediately.
To obtain an accurate reading of a new spark
plug:
1. Accelerate at full throttle on a straight
2. Push the engine stop button and pull the
clutch lever in to release the clutch.
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.
Metallic specks indicate lean jetting that is
removing metal from the piston. Black sooty
streaks on the porcelain indicate rich jetting.
Improperly tightened spark plugs 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.
(1) insulator (3) side electrode
(2) center electrode
Spark Plug Coloring Guidelines
Remember that in addition to improper jetting:
• A lean condition can be caused by air leaks in
the insulator tract, in the center crankcase
joint and leaking ignition side crank seal.
Insufficient oil on the air cleaner may also
cause a lean condition.
• A rich condition may be caused by a leaking
primary drive side seal — that draws
transmission oil into the fuel/air mixture.
Excessive smoking will occur. Failure to
remove the air cleaner housing cover for dry
conditions may also cause a rich condition.
Pressure/vacuum testing your engine on a
regular basis to detect air leaks is
recommended. See your Honda dealer.
The same simple throttle opening
identification system used in the
Break-in section of this manual can also be
used to accurately identify where carburetion
problems occur, should they arise (page 16).
NOTICE
NOTICE
(2)
(3)
(1)
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
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