Tuning For Special Conditions; Spark Plug Coloring Indications - Honda CR250R 2004 Owner's Manual

TUNING FOR SPECIAL CONDITIONS

Once you've adjusted the carburetor for temperature and altitude, it shouldn't
need major readjustment unless race conditions change drastically. However,
there are some unique atmospheric conditions or race day situations that may
require additional adjustments. They are as follows.
NOTE:
•
To prevent engine damage, always adjust the main jet before adjusting the jet
needle. Always choose the next richer jet if there is any doubt so there is a
margin for safety.
Main Jet •
Go richer on the main jet, by one number, when: the track has a very
long straightaway or uphill section, a high percentage of sand, or the
track is muddy.
•
Go leaner on the main jet, by one number, when: it is very humid or
raining, or it is hotter than 113 degrees F.
NOTE:
•
After using the chart, and making any adjustments for special conditions, it
shouldn't be necessary to go more than one jet size richer or leaner to fine tune
your CR. If larger jetting changes are necessary, check for worn crankshaft
seals, air leaks, blocked or restricted exhaust or fuel systems, or a dirty air
cleaner.

SPARK PLUG COLORING INDICATIONS

Dark brown to light tan color with
Normal
dry electrode
Overheating Light gray or white color
Wet and sooty
Wet
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 carburation
problems occur, should they arise. (See page 3)
—
Mixture is Lean*
Mixture is Rich**
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