Jack Phelps' Pages
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Your Plugs!
It seems
that most V Star owners just can't resist the temptation to make
modifications to their rides. Often the first change is to more
free-flowing intake and exhaust systems. Unfortunately, many of
these mods are made without making corresponding changes to maintain
a proper air/fuel mixture. Running too rich can cause plug fouling
and poor fuel economy; too lean and your pipes can discolor and, in
extreme cases, plugs and even pistons can burn. Either condition can
cause sluggish performance. For the home machanic without
sophisticated shop equipment, spark plugs can be an important
diagnostic tool.
Yamaha
recommends that you check your spark plugs every 4,000 miles and
change them every 8,000. I would recommend that you check them after
making any changes to your exhaust or intake systems. Remove the
plugs as per instructions in your owner's manual, then check the
condition and color of the plugs:
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Your plugs
should be a nice tan or light brown color. The electrode should not
be pitted, and the ceramic insulator should be smooth and not cracked. |
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This plug
is covered with a dry, black carbon coating. It indicates a rich fuel
mixture, which could be caused by inaccurate jetting, excessive
choking, or a dirty or obstructed air cleaner. |
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This plug
is white or ash gray in color, indicating a very lean fuel mixture.
Note that the center electrode is burned. This is caused by
inaccurate jetting, over-advanced timing,
engine overheating, or leaks in the air intake system. |
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