Checking The Air Induction System; Air Injection; Air Cut-Off Valve - Yamaha YZF-R1(B) 2012 Service Manual

EAS27060

CHECKING THE 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 neg-
ative 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 (1112 to 1292
°F).

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.
AIR INDUCTION SYSTEM
A. From the air filter case
B. To the cylinder head
1. Check:
• Hoses
Loose connections → Connect properly.
Cracks/damage → Replace.
2. Check:
• Reed valve
• Reed valve stopper
• Reed valve base
Cracks/damage → Replace the reed
valve assembly.
3. Measure:
• Reed valve bending limit "a"
Out of specification → Replace the reed
valve.
Reed valve bending limit
0.4 mm (0.016 in)
7-25