Honda 2005 VTX1800C Owner's Manual page 218

Crankcase Emission Control System
The engine is equipped with a closed
crankcase system to prevent discharging
crankcase emissions into the atmosphere.
Blow-by gas is returned to the combustion
chamber through the air cleaner and the
intake manifold.
Emission Control Systems
Problems That May Affect Motorcycle
Exhaust Emissions
If you are aware of any of the following
symptoms, have the vehicle inspected and
repaired by your authorized Honda
motorcycle dealer.
Symptoms:
1. Hard starting or stalling after starting
2. Rough idle
3. Misfiring or backfiring during
acceleration
4. After-burning (backfiring)
5. Poor performance (driveability) and
poor fuel economy
Technical Information
209