Yamaha Tracer MT09TRA - Service manual > Engine inspection

Measure the compression pressure

The following procedure applies to all of the cylinders.

TIP

Insufficient compression pressure will result in a loss of performance.

1. Measure:

• Valve clearance Out of specification → Adjust.

  Refer to "ADJUSTING THE VALVE CLEARANCE"

2. Start the engine, warm it up for several minutes, and then turn it off.

3. Remove:

• Fuel tank front cover/Front side panel/Front side cowling.

  Refer to "GENERAL CHASSIS (2)"

• Passenger seat/Rider seat.

  Refer to "GENERAL CHASSIS (1)"

• Fuel tank cover.

  Refer to "GENERAL CHASSIS (3)"

• Fuel tank.

  Refer to "FUEL TANK"

• Air filter case.

  Refer to "GENERAL CHASSIS (3)"

• Air cut-off valve.

  Refer to "AIR INDUCTION SYSTEM"

• Ignition coils
• Spark plugs.

  Refer to "CAMSHAFTS"

NOTICE

Before removing the spark plugs, use compressed air to blow away any dirt accumulated in the spark plug wells to prevent it from falling into the cylinders.

4. Install:

• Compression gauge "1"
• Extension "2"

Compression gauge 90890-03081

Engine compression tester YU-33223

Extension 90890-04136

5. Measure:

Compression pressure.

Out of specification → Refer to steps (c) and (d).

Standard compression pressure (at sea level)

1530 kPa/680 r/min (15.3 kgf/cm²/680 r/min, 217.6 psi/680 r/min)

Minimum-maximum 1330-1710 kPa/680 r/min (13.3- 17.1 kgf/cm²/680 r/min, 189.2- 243.2 psi/680 r/min)

a. Set the main switch to "ON".

b. With the throttle wide open, crank the engine until the reading on the compression gauge stabilizes.

WARNING

To prevent sparking the plug, remove all ignition coil couplers and fuel injector couplers before cranking the engine.

TIP

The difference in compression pressure between cylinders should not exceed 100 kPa (1 kg/cm², 15 psi).

c. If the compression pressure is above the maximum specification, check the cylinder head, valve surfaces and piston crown for carbon deposits.

Carbon deposits → Eliminate.

d. If the compression pressure is below the minimum specification, pour a teaspoonful of engine oil into the spark plug bore and measure again.

Refer to the following table.

6. Install:

• Spark plugs

Spark plug 13 Nm (1.3 m*kgf, 9.4 ft*lbf)

7. Install:

• Ignition coils.

  Refer to "CAMSHAFTS"

• Air cut-off valve.

  Refer to "AIR INDUCTION SYSTEM"

• Air filter case.

  Refer to "GENERAL CHASSIS (3)"

• Fuel tank.

  Refer to "FUEL TANK"

• Fuel tank cover.

  Refer to "GENERAL CHASSIS (3)"

• Rider seat/Passenger seat.

  Refer to "GENERAL CHASSIS (1)"

• Front side cowling/Front side panel/Fuel tank front cover.

  Refer to "GENERAL CHASSIS (2)"

See also: