Safety Valve Check - PIAGGIO Beverly 250 USA Workshop Manual

Beverly 250 USA
To check the Canister, it is necessary to proceed
with its removal, whilst keeping the two hoses at-
tached.
• Shake the Canister and ensure it emits no noise.
• Using a compressed air gun, blow the 3 ducts
and ensure this does not result in a pressure build-
up inside the Canister.
• Ensure the airflow is undisturbed and no carbon
residues exit the hose.
Replace the Canister if noisy, clogged up, or leak-
ing carbon residues.

Safety valve check

The Canister is cleaned by an air flow controlled by the vacuum inlet located on the intake manifold.
To guarantee the correct operation of the engine, the mass air flow must not be excessively large; this
is obtained by using a narrow section (0.9mm) for the inlet on the intake manifold.
The Canister tubing connections comprise the installation of a safety valve.
This is a unidirectional valve that ensures the air flow towards the manifold when the control vacuum
is over 200mbar.
The engine vacuum at idle causes a weak air flow that can be easily compensated for with the idle
adjustment parameters.
When the vehicle is stationary, the safety valve will be shut due to the lack of control vacuum; for this
reason, any expansion of the fuel tank will not pollute the intake manifold thus preventing engine floods.
The valve should preferably be removed from the
vehicle upon inspection; alternatively, it will be suf-
ficient to access the tubing on the manifold side.
• Connect the MITYVAC pump on the engine side
duct.
• Set the pump control onto "vacuum", then slowly
apply vacuum to check the valve opening thresh-
old.
If different pressures are found, replace the valve.
N.B. If the opening vacuum is too high, it causes a
lack of active carbon regeneration; on the other
hand, if it is too low, it increases the air flow rate to
the engine, thus causing a poor fuel-oxygen mix-
ture at idle.
Maintenance
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