Honda 2004 CRF150F Owner's Manual page 89

Spark Arrester
3. Use a brush to remove carbon deposits from
the spark arrester screen. Be careful to avoid
damaging the spark arrester screen. The
spark arrester must be free of breaks and
holes. Replace, if necessary. Check the
gasket. Replace, if necessary.
80
Servicing Your Honda
4. Install the spark arrester and the gasket in the
muffler and tighten the three bolts securely.