Sym MB10A7-A series Service Manual page 212

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Secondary Air Introduction System
Construction
4.
Engine
Flesh air
Mixture gas
First burn exhaust
Purged exhaust gas
Vacuum
This system contained AICV (air Injection Cut Valve), R/V (Reed Valve) and other intake components.
2. Principle of operation:
Secondary air is introduced into exhaust manifold so that CO and HC in the exhaust will be burned
again under a state of rich oxygen and appropriate temperature and be turned into harmless CO
H O.
2
The opening and closing of the exhaust valve can generate a positive or a negative pressure pulse
inside a motorcycle's exhaust system. Exhaust gas is controlled by a reed valve. When pressure
inside the exhaust manifold is negative, reed valve will be sucked open by the negative pressure
and outside air will enter to mix with CO, HC, thus generating a secondary burn reaction and
turning them into harmless gases. When pressure inside the exhaust manifold is positive, reed
valve will close to prevent exhaust back up and enter into the secondary air cleaner.
Air cut-off valve (AICV) will cut off the secondary air supply during engine fuel returning cycle to
reduce after-burning noises.
13-5
To this chapter contents
Carburetor
Intake valve
Flesh air
Exhaust valve
Exhaust pipe
13. Emission Control System
Secondary air filter
Vacuum hose
Cylinder head
Reed valve
Air injection cut valve
,
2