Yamaha T135SE, Service Manual

Page: 226 / 349

CARB
AIR INDUCTION SYSTEM
6-14
AIR INDUCTION SYSTEM
AIR INJECTION
The air induction system burns unburned
exhaust gases by injecting fresh air (secondary
air) into the exhaust port, reducing the
emission of hydrocarbons.
When there is negative pressure at the exhaust
port, the reed valve opens, allowing secondary
air to flow into the exhaust port. The required
temperature for burning the unburned exhaust
gases is approximately 600 to 700 ° C.
AIR CUT-OFF VALVE
The air cutoff valve is operated by the intake gas
pressure through the piston valve diaphragm.
Normally, the air cut-off valve is open to allow
fresh air to flow into the exhaust port (
å
to
∫
).
During sudden deceleration (the throttle valve
suddenly closes), negative pressure (
ç
) is gen-
erated and the air cutoff valve is closed in order
to prevent after-burning. Additionally, at high
engine speeds and when the pressure decreas-
es, the air cut-off valve automatically closes to
guard against a loss of performance.
å
From the air filter
∫
To the cylinder head
ç
To the intake manifold
å
∫
ç
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