Snowmobile Yamaha Phazer PZ50W, PZ50GTW, PZ50FXW, PZ50MW, PZ50VTW, PZ50MPW. Manual - part 49

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VALVES AND VALVE SPRINGS

REMOVAL

The following procedure applies to all of the valves
and related components.

NOTE:

Before removing the internal parts of the cylinder
head (e.g., valves, valve springs, valve seats),
make sure the valves properly seal. 

1. Remove:

• Valve lifter 1 
• Valve pad 2 

NOTE:

Make a note of the position of each valve lifter and
valve pad so that they can be reinstalled in their
original place. 

2. Inspect:

• Valve

(for leakage) 
Leakage at the valve seat 

→ Check the valve

face, valve seat, and valve seat width.

Inspection steps:

• Pour a clean solvent 

a into the intake and

exhaust ports. 

• Check that the valves properly seal.

NOTE:

There should be no leakage at the valve seat 1. 

3. Remove:

• Valve cotters 1 

NOTE:

Remove the valve cotters by compressing the valve
spring with the valve spring compressor 2 and
attachment 3. 

Valve spring compressor:

90890-04019, YM-04019

Valve spring compressor attach-
ment:

Intake valve:

90890-04114, YM-04114

Exhaust valve:

90890-04108, YM-04108

2

3

1

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VALVES AND VALVE SPRINGS

4. Remove:

• Upper spring seat 1 
• Valve spring 2 
• Valve 3 
• Valve stem seal 4 
• Lower spring seat 5 

NOTE:

Identify the position of each part very carefully so
that it can be reinstalled in its original place. 

INSPECTION

1. Measure:

• Valve-stem-to-valve-guide clearance

Out of specification 

→ Replace the valve

guide.

Valve-stem-to-valve-guide clearance = 

Valve guide inside diameter 

a – 

Valve stem diameter 

b 

Valve-stem-to-valve-guide clearance:

Intake:

0.010 ~ 0.037 mm
(0.0004 ~ 0.0015 in)
<Limit>: 0.08 mm (0.0031 in)

Exhaust:

0.025 ~ 0.052 mm
(0.0010 ~ 0.0020 in)
<Limit>: 0.10 mm (0.0039 in)

2. Replace:

• Valve guide

NOTE:

To ease valve guide removal and installation, and
to maintain the correct fit, heat the cylinder head to
100 °C (212 °F) in an oven. 

Replacement steps:

• Remove the valve guide with the valve guide

remover 1.

• Install the new valve guide with the valve guide

installer 2 and valve guide remover 1.

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VALVES AND VALVE SPRINGS

• After installing the valve guide, bore the valve

guide with the valve guide reamer 3 to obtain
the proper valve-stem-to-valve-guide clearance.

NOTE:

After replacing the valve guide, reface the valve
seat.

3. Eliminate:

• Carbon deposits 

(from the valve face and valve seat)

4. Inspect:

• Valve face

Pitting/wear 

→ Grind the valve face.

• Valve stem end

Mushroom shape or diameter larger than the
body of the valve stem 

→ Replace the valve.

5. Measure:

• Valve margin thickness 

a 

Out of specification 

→ Replace the valve.

Valve guide remover (ø4):

90890-04111, YM-04111

Valve guide installer (ø4):

90890-04112, YM-04112

Valve guide reamer (ø4):

90890-04113, YM-04113

Valve margin thickness:

Intake:

0.5 ~ 0.9 mm (0.0197 ~ 0.0354 in)

Exhaust:

0.5 ~ 0.9 mm (0.0197 ~ 0.0354 in)

6. Measure:

• Valve stem runout 

Out of specification 

→ Replace the valve.

NOTE:

• When installing a new valve, always replace the

valve guide. 

• If the valve is removed or replaced, always

replace the oil seal. 

7. Eliminate:

• Carbon deposits

(from the valve face and valve seat)

8. Inspect:

• Valve seat

Pitting/wear 

→ Replace the cylinder head.

Valve stem runout:

0.01 mm (0.0004 in)

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VALVES AND VALVE SPRINGS

9. Measure:

• Valve seat width 

a 

Out of specification 

→ Replace the cylinder

head.

Measurement steps:

• Apply Mechanic’s blueing dye (Dykem) 1 onto

the valve face.

• Install the valve into the cylinder head.
• Press the valve through the valve guide and

onto the valve seat to make a clear impression.

• Measure the valve seat width.

NOTE:

Where the valve seat and valve face contacted one
another, the blueing will have been removed. 

Valve seat width:

Intake:

0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)

Exhaust: 

1.2 ~ 1.4 mm (0.0472 ~ 0.0551 in)
<Limit>: 1.9 mm (0.0748 in)

10. Lap:

• Valve face
• Valve seat

NOTE:

After replacing the cylinder head or replacing the
valve and valve guide, the valve seat and valve
face should be lapped. 

Lapping steps:

• Apply a coarse lapping compound 

a to the

valve face.

CAUTION:

Do not let the lapping compound enter the gap
between the valve stem and the valve guide. 

• Apply molybdenum disulfide oil onto the valve

stem.