Air Induction System; Air Injection; Air Cutoff Valve - Yamaha XV16AL Service Manual

CARB

AIR INDUCTION SYSTEM

EAS00507
AIR INDUCTION SYSTEM

AIR INJECTION

The air induction system burns unburned
exhaust gases by injecting fresh air (sec-
ondary air) into the exhaust port, reducing
the emission of hydrocarbons.
When there is negative pressure at the
exhaust port, the reed valve opens, allow-
ing secondary air to flow into the exhaust
port. The required temperature for burning
the unburned exhaust gases is approxi-
mately 600 to 700 ˚C (1,112 to 1,292 ˚F).
EAS00508

AIR CUTOFF VALVE

The air cutoff valve is operated by the
intake gas pressure through the piston
valve diaphragm. Normally, the air cutoff
valve is open to allow fresh air to flow into
the exhaust port. During sudden decelera-
tion (the butterfly valve suddenly closes),
negative pressure is generated and the air
cutoff valve is closed in order to prevent
after-burning.
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Additionally, at high engine speeds and
when the pressure decreases, the air cutoff
valve automatically closes to guard against
a loss of performance due to self-EGR
(Exhaust Gas Recirculation).
1 During normal operation, the air cutoff
valve is open.
2 During sudden deceleration (the butterfly
valve suddenly closes), the air cutoff valve
closes.
3 At high engine speeds and when the
pressure decreases, the air cutoff valve is
closed.
Å From the air cleaner
ı To the reed valve
Ç To the carburetor joint
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