Honda CR125R 2006 Owner's Manual page 110

Carburetor Adjustments & Tuning Tips
(19)
(20) air vent hoses (21) overflow hose
Spark Plug Reading
Refer to Spark Plug, page 48.
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.
106
Adjustments for Competition
NOTICE
Using spark plugs with an improper heat range
or incorrect reach can cause engine damage.
Before removing the spark plug, clean the spark
(20) plug area thoroughly to prevent dirt from
entering 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.
NOTICE
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.
(1)
(1) insulator (3) side electrode
(2) center electrode
Spark Plug Coloring Guidelines
Condition Spark Plug Appearance
Normal Dark brown to light tan
color with dry electrode
Overheating Light gray or white color
(Lean)
Wet Wet or sooty
(Rich)
Remember that in addition to improper jetting:
• A lean condition can be caused by air leaks in
the inlet tract, in the center crankcase joint
and leaking ignition side crank seal.
• 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.
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 15).
(2)
(3)
Mixture
correct
lean
rich