Yamaha YFM400AS Owner's Manual page 160

1. Do not touch the glass part of the bulb.
CAUTION:
_
Do not touch the glass part of the head-
light bulb to keep it free from oil, otherwise
the transparency of the glass, the luminos-
ity of the bulb, and the bulb life will be ad-
versely affected. Thoroughly clean off any
dirt and fingerprints on the headlight bulb
using a cloth moistened with alcohol or
thinner.
_
5. Install the bulb holder by turning it clock-
wise.
6. Install the bulb holder cover at the rear of
the headlight.
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