Yamaha Tracer MT09TRA - Service manual > Air induction system

1. Air filter case

2. Air induction system hose (air filter case to air cut-off valve)

3. Air cut-off valve

4. Air induction system hose (air cut-off valve to reed valve cover)

Checking the 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 ºC (1112 to 1292 ºF).

Air cut-off valve

The air cut-off valve is controlled by the signals from the ECU in accordance with the combustion 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 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. Check:

• Hoses

Loose connections → Connect properly.

Cracks/damage → Replace.

2. Check:

• Reed valve
• Reed valve stopper
• Reed valve seat

Cracks/damage → Replace the reed valve assembly.

3. Measure:

• Reed valve bending limit "a"

Out of specification → Replace the reed valve assembly.

Reed valve bending limit 0.4 mm (0.02 in)

4. Check:

• Air cut-off valve

Cracks/damage → Replace.

5. Check

• Air induction system solenoid

Installing the air induction system

1. Install:

• Reed valve plate "1"

TIP

• Align the projection "a" on the cylinder head cover with the notch "b" in the reed valve plate "1".
• Align the projection "c" on the cylinder head cover with the hole "d" in the reed valve plate "1".

2. Install:

• Reed valve assembly 1
• Reed valve assembly 2

TIP

• Install the reed valve assembly 1 so that the open side turns to the exhaust side of the engine.
• Install the reed valve assembly 2 so that the open side turns to the intake side of the engine.

A. Reed valve assembly 1

B. Reed valve assembly 2

C. Exhaust side

3. Install:

• Reed valve cover

Reed valve cover bolt 10 Nm (1.0 m*kgf, 7.2 ft*lbf) LOCTITE

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