Yamaha MT-03 - Service manual > Rocker arms and camshaft

Removing the rocker arms and camshaft

1. Loosen:

• Locknuts
• Adjusting screws

2. Remove:

• Camshaft retainer "1"

3. Remove:

• Intake rocker arm shaft
• Exhaust rocker arm shaft
• Intake rocker arm
• Exhaust rocker arm

NOTE:

Remove the rocker arm shafts with the slide hammer bolt "1" and weight "2".

Slide hammer bolt 90890-01083 Weight 90890-01084

4. Remove:

• Camshaft

Checking the camshaft

1. Check:

• Camshaft lobes

Blue discoloration/pitting/scratches → Replace the camshaft and camshaft sprocket.

2. Measure:

• Camshaft lobe dimensions "a" and "b".

  Out of specification → Replace the camshaft.

Camshaft lobe dimensions Intake "a" 43.488-43.588 mm (1.7121-1.7161 in) <Limit>: 43.388 mm (1.7062 in) "b" 36.959-37.059 mm (1.4551-1.4590 in) <Limit>: 36.840 mm (1.4504 in) Exhaust "a" 43.129-43.229 mm (1.6980-1.7019 in) <Limit>: 42.983 mm (1.6922 in) "b" 37.007-37.107 mm (1.4570-1.4609 in) <Limit>: 36.886 mm (1.4522 in)

3. Measure:

• Camshaft runout

Out of specification → Replace.

Camshaft runout limit 0.040 mm (0.0016 in)

Checking the decompression system

1. Check:

• Decompression system

a. Check the decompression system with the camshaft sprocket installed on and the decompressor pin installed in the camshaft.

b. Check that the decompressor lever pin "1" projects from the camshaft.

c. Check that the decompressor cam "2" moves smoothly.

Checking the rocker arms and rocker arm shafts

The following procedure applies to both of the rocker arms and rocker arm shafts.

1. Check:

• Rocker arm

Damage/wear → Replace.

2. Check:

• Rocker arm shaft

Blue discoloration/excessive wear/pitting/ scratches → Replace or check the lubrication system.

3. Measure:

• Rocker arm inside diameter

Out of specification → Replace.

Rocker arm inside diameter 12.000-12.018 mm (0.4724-0.4731 in) <Limit>: 12.036 mm (0.4739 in)

4. Measure:

• Rocker arm shaft outside diameter

Out of specification → Replace.

Rocker arm shaft outside diameter 11.981-11.991 mm (0.4717-0.4721 in) <Limit>: 11.955 mm (0.4707 in)

5. Calculate:

• Rocker-arm-to-rocker-arm-shaft clearance

NOTE:

Calculate the clearance by subtracting the rocker arm shaft outside diameter from the rocker arm inside diameter.

Above 0.081 mm (0.0032 in) → Replace the defective part(s).

Rocker-arm-to-rocker-arm-shaft clearance 0.009-0.037 mm (0.0004-0.0015 in) <Limit>: 0.081 mm (0.0032 in)

Installing the camshaft and rocker arms

1. Install:

• Bearing "1"

(onto the camshaft)

NOTE:

• Apply engine oil to the bearing.
• Install the bearing so that the seal is facing "a" the camshaft.

Installed depth "b" 0 mm (0 in)

2. Lubricate:

• Camshaft
• Decompressor lever pin
• Decompressor lever

Recommended lubricant Camshaft Molybdenum disulfide oil Camshaft bearing Engine oil

3. Install:

• Decompressor lever pin "1"
• Decompressor lever "2"

NOTE:

Install the decompressor lever pin "1" and decompressor lever "2" in the camshaft "3" as shown in the illustration.

4. Install:

• Camshaft "1"

NOTE:

Install the camshaft on the slot "a" facing up.

5. Lubricate:

• Rocker arm shafts

Recommended lubricant Engine oil

6. Install:

• Exhaust rocker arm "1"
• Exhaust rocker arm shaft "2"
• Intake rocker arm
• Intake rocker arm shaft

NOTE:

• Use a slide hammer bolt "3" to install the rocker arm shaft.
• Make sure the rocker arm shaft (intake and exhaust) is completely pushed into the cylinder head.

Slide hammer bolt 90890-01083

7. Install:

• Camshaft retainer
• Camshaft retainer bolts

Camshaft retainer bolts 10 Nm (1.0 m*kg, 7.2 ft*lb) LOCTITE

See also: