Yamaha XT660 2004, Service Manual

Page: 376 / 463

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FI
AIR INDUCTION SYSTEM
EAS00507
AIR INDUCTION SYSTEM
AIR INJECTION
The air induction system burns unburned
exhaust gases by injecting fresh air (second-
ary 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
(1,112 to 1,292 °F).
EAS00917
AIR CUT-OFF VALVE
The air cut-off valve is controlled by the signals
from the ECU in accordance with the combus-
tion conditions. Ordinarily, the air cut-off valve
opens to allow the air to flow during idle and
closes to cut-off the flow when the vehicle is
being driven. However, if the coolant tempera-
ture is below the specified value, the air cut-off
valve remains open and allows the air to flow
into the exhaust pipe until the temperature
becomes higher than the specified value.
È
From the air filter case
É
To the cylinder head
1
The air cut-off valve is closed.
2
The air cut-off valve is open.
È
É
È
1
2