Honda RUCKUS NPS50 2022 Owner's Manual page 88

Emission Control Systems
Exhaust Emission Control System
The exhaust emission control system consists of
appropriate carburetor settings, and no
adjustment should be made except idle speed
adjustment with the throttle stop screw.
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Secondary Air Injection System
The secondary air injection system adds filtered
air into the exhaust gas to help improve
emission control performance.
84
Crankcase Emissions 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
carburetor.