Table of Contents
Advertisement
After installing the carburetor, check the air vent
hoses (20) and overflow hose (21) for kinking or
pinching and correct routing as necessary.
(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
(20)
simply turn off the engine and pull the plug for
inspection.
Use a new spark plug. Inspect the plug before
installing it.
NOTICE
(21)
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
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.
Carburetor Adjustments & Tuning Tips
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) insulator
(2) center electrode
Spark Plug Coloring Guidelines
Condition
Normal
Overheating
(Lean)
Wet
(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)
(1)
(3)
(3) side electrode
Spark Plug Appearance
Mixture
Dark brown to light tan
correct
color with dry electrode
Light gray or white color
lean
Wet or sooty
rich
109
Adjustments for Competition
Advertisement
Table of Contents
