Honda CB650F 2018 Owner's Manual page 120

Emission Control Systems
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 throttle body.
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Fuel Permeation Emission Control
The fuel tank, fuel hoses, and fuel vapor charge
hoses use fuel permeation control technologies
to prevent fuel vapor emissions. Tampering with
these components to reduce or defeat the
effectiveness of the fuel permeation
technologies is prohibited.