Snowmobile Yamaha FX10X, FX10RTX, FX10RTRX, FX10RTRAX, FX10MTX, FX10MTRX, FX10MTRAX. Manual - part 53

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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>: 0.080 mm (0.0031 in)

Exhaust:

0.025 ~ 0.052 mm
(0.0010 ~ 0.0020 in)
<Limit>: 0.100 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.

Valve guide position 

a:

14.8 ~ 15.2 mm
(0.583 ~ 0.598 in)

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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.

Valve guide remover (ø4.5):

90890-04116

Valve guide remover (4.5 mm):

YM-04116

Valve guide installer (ø4.5):

90890-04117

Valve guide installer (4.5 mm):

YM-04117

Valve guide reamer (ø4.5):

90890-04118

Valve guide reamer (4.5 mm):

YM-04118

5. Measure:

• Valve margin thickness 

a 

Out of specification 

→ Replace the valve.

Valve margin thickness:

Intake:

0.80 ~ 1.20 mm 
(0.0315 ~ 0.0472 in)

Exhaust:

0.50 ~ 0.90 mm 
(0.0197 ~ 0.0354 in)

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VALVES AND VALVE SPRINGS

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 valve stem 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:

0.010 mm (0.0004 in)

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:

0.90 ~ 1.10 mm 
(0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)

Exhaust: 

0.90 ~ 1.10 mm 
(0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)

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VALVES AND VALVE SPRINGS

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. 

• Install the valve into the cylinder head.
• Turn the valve until the valve face and valve

seat are evenly polished, then clean off all of
the lapping compound.

NOTE:

For the best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands. 

• Apply a fine lapping compound to the valve face

and repeat the above steps. 

• After every lapping procedure, be sure to clean

off all of the lapping compound from the valve
face and valve seat. 

• Apply Mechanic’s blueing dye (Dykem) 

b 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 

c again. If the

valve seat width is out of specification, reface
and lap the valve seat.