Air Induction System; Air Injection; Air Cut-Off Valve - Yamaha XT660Z 2008 Service Manual

AIR INDUCTION SYSTEM

EAS00507

AIR INJECTION

The air induction system burns unburned ex-
haust 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 (1,112 to
1,292 °F).
AIR INDUCTION SYSTEM
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 be-
ing driven. However, if the coolant temperature
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.
A. From the air filter case
B. To the cylinder head
1. The air cut-off valve is closed.
2. The air cut-off valve is open.
B
7-11
1
A
2
A