Yamaha Fz6 N Service Manual

							
VALVES AND VALVE SPRINGS
5-20
For installation, reverse the removal proce-
dure.
Removing the valves and valve springs
Order Job/Parts to remove Q’ty Remarks 
						

							
VALVES AND VALVE SPRINGS
5-21
EAS24280
REMOVING THE VALVES
The following procedure applies to all of the 
valves and related components.
NOTE:
Before removing the internal parts of the cylin-
der 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. Check:
 Valve sealing Leakage at the valve seat  → Check the 
valve face, valve seat, and valve seat width.
Refer to CHECKING THE VALVE SEATS 
on page 5-23.
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a. Pour a clean solvent “a” into the intake and 
exhaust ports.
b. Check that the valves properly seal.
NOTE:
There should be no leakage at the valve seat 
“1”.
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3. Remove:  Valve cotters “1”
NOTE:
Remove the valve cotters by compressing the 
valve springs with the valve spring compressor 
“2” and the valve spring compressor attach-
ment “3”.
4. Remove:
 Upper spring seat “1”
 Valve spring outer “2”
 Valve spring inner (intake only) “3”
Valve “4”
 Valve stem seal “5”
 Lower spring seat “6”
NOTE:
Identify the position of each part very carefully 
so that it can be reinstalled in its original place.
Valve spring compressor 90890-04019
YM-04019
Valve spring compressor 
attachment 90890-04108
Valve spring compressor 
adapter 22 mm YM-04108 
						

							
VALVES AND VALVE SPRINGS
5-22
EAS24290
CHECKING THE VALVES AND VALVE 
GUIDES
The following procedure applies to all of the 
valves and valve guides.
1. Measure: Valve-stem-to-valve-guide clearance
Out of specification  → Replace the valve 
guide.
2. Replace:  Valve guideNOTE:
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.
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a. Remove the valve guide with the valve 
guide remover “1”.
b. Install the new valve guide with the valve  guide installer “2” and valve guide remover 
“1”.
c. 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.
 Valve-stem-to-valve-guide clearance =
Valve guide inside diameter “a” -
Valve stem diameter “b”
Valve-stem-to-valve-guide clear-
ance Valve-stem-to-valve-guide clear-
ance (intake)
0.010–0.037 mm (0.0004–
0.0015 in)
Limit 0.080 mm (0.0032 in)
Valve-stem-to-valve-guide clear-
ance (exhaust)
0.025–0.052 mm (0.0010–
0.0020 in)
Limit 0.100 mm (0.0039 in) 
						

							
VALVES AND VALVE SPRINGS
5-23
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3. Eliminate: Carbon deposits (from the valve face and valve seat)
4. Check: 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.
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.
EAS24300
CHECKING THE VALVE SEATS
The following procedure applies to all of the 
valves and valve seats.
1. Eliminate:  Carbon deposits (from the valve face and valve seat)
2. Check: Valve seat Pitting/wear  → Replace the cylinder head.
3. Measure:  Valve seat width “a” Out of specification  → Replace the cylinder 
head.
Valve guide remover (ø4) 90890-04111
Valve guide remover (4.0 mm)
YM-04111
Valve guide installer (ø4) 90890-04112
Valve guide installer (4.0 mm) YM-04112
Valve guide reamer (ø4)
90890-04113
Valve guide reamer (4.0 mm) YM-04113
Valve margin thickness
Valve margin thickness D
(intake)0.60–0.80 mm (0.0236–0.0315
in)
Limit 0.5 mm (0.02 in)
Valve margin thickness D
(exhaust) 0.60–0.80 mm (0.0236–0.0315
in)
Limit 0.5 mm (0.02 in)
Valve stem runout
Valve stem runout0.040 mm (0.0016 in)
Valve seat width
Valve seat width C (intake)0.90–1.10 mm (0.0354–0.0433
in)
Limit 1.6 mm (0.06 in)
Valve seat width C (exhaust) 0.90–1.10 mm (0.0354–0.0433
in)
Limit 1.6 mm (0.06 in) 
						

							
VALVES AND VALVE SPRINGS
5-24
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a. Apply Mechanic’s blueing dye (Dykem) “b” onto the valve face.
b. Install the valve into the cylinder head.
c. Press the valve through the valve guide  and onto the valve seat to make a clear 
impression.
d. Measure the valve seat width.
NOTE:
Where the valve seat and valve face contacted 
one another, the blueing will have been 
removed.
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4. 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.
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a. Apply a coarse lapping compound “a” to  the valve face.
CAUTION:
ECA13790
Do not let the lapping compound enter the 
gap between the valve stem and the valve 
guide. b. Apply molybdenum disulfide oil onto the 
valve stem.
c. Install the valve into the cylinder head.
d. 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.
e. Apply a fine lapping compound to the valve face and repeat the above steps.
f. After every lapping procedure, be sure to  clean off all of the lapping compound from 
the valve face and valve seat.
g. Apply Mechanic’s blueing dye (Dykem) “b”  onto the valve face. 
						

							
VALVES AND VALVE SPRINGS
5-25
h. Install the valve into the cylinder head.
i. Press the valve through the valve guide and onto the valve seat to make a clear 
impression.
j. Measure the valve seat width “c” again. If  the valve seat width is out of specification, 
reface and lap the valve seat.
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EAS24310
CHECKING THE VALVE SPRINGS
The following procedure applies to all of the 
valve springs.
1. Measure: Valve spring free length “a”
Out of specification  → Replace the valve 
spring. 2. Measure:
 Compressed valve spring force “a” Out of specification  → Replace the valve 
spring.
Inner spring
Free length (intake)
37.04 mm (1.46 in)
Limit 35.20 mm (1.39 in)
Free length (exhaust) 41.79 mm (1.65 in)
Limit
39.70 mm (1.56 in)
Outer spring
Free length (intake) 38.40 mm (1.51 in)
Limit 36.50 mm (1.44 in)
b. Installed length
Inner spring
Installed compression spring
force (intake)
69–79 N (15.51–17.76 lbf)
(7.04–8.06 kgf)
Installed compression spring
force (exhaust) 160–184 N (35.97–41.36 lbf)
(16.32–18.76 kgf)
Outer spring
Installed compression spring
force (intake) 114–132 N (25.63–29.67 lbf)
(11.62–13.46 kgf)
Inner spring
Installed length (intake) 30.02 mm (1.18 in)
Installed length (exhaust) 36.12 mm (1.42 in)
Outer spring
Installed length (intake)
32.52 mm (1.28 in) 
						

							
VALVES AND VALVE SPRINGS
5-26
3. Measure: Valve spring tilt “a” Out of specification  → Replace the valve 
spring.
EAS24320
CHECKING THE VALVE LIFTERS
The following procedure applies to all of the 
valve lifters.
1. Check:
 Valve lifter Damage/scratches  → Replace the valve 
lifters and cylinder head.
EAS24340
INSTALLING THE VALVES
The following procedure applies to all of the 
valves and related components.
1. Deburr:  Valve stem end (with an oil stone)
2. Lubricate: Valve stem “1”
 Valve stem seal “2”
(with the recommended lubricant)
3. Install: Valve “1”
 Lower spring seat “2”
 Valve stem seal “3”
 Valve spring inner (intake only) “4”
 Valve spring outer “5”
 Upper spring seat “6” (into the cylinder head)
NOTE:
 Make sure each valve is installed in its origi-
nal place.
 Install the valve springs with the larger pitch 
“a” facing up.
Spring tilt limit Spring tilt (intake)2.5  °/1.6 mm (0.06 in)
Spring tilt (exhaust)
2.5  °/1.8 mm (0.07 in)
Spring tilt (intake) 2.5  °/1.7 mm (0.07 in)
Recommended lubricant
Molybdenum disulfide oil 
						

							
VALVES AND VALVE SPRINGS
5-27
4. Install: Valve cotters “1”
NOTE:
Install the valve cotters by compressing the 
valve spring with the valve spring compressor 
“2” and the valve spring compressor attach-
ment “3”. 5. To secure the valve cotters onto the valve 
stem, lightly tap the valve tip with a soft-
face hammer.
CAUTION:
ECA13800
Hitting the valve tip with excessive force 
could damage the valve.
6. Lubricate:
 Valve pad “1”
 Valve lifter “2” (with the recommended lubricant)
NOTE:
 Lubricate the valve lifter and valve pad with molybdenum disulfide oil.
 The valve lifter must move smoothly when 
rotated with a finger.
 Each valve lifter and valve pad must be rein-
stalled in its original position.
b. Smaller pitch
Valve spring compressor 90890-04019
YM-04019
Valve spring compressor 
attachment
90890-04108
Valve spring compressor 
adapter 22 mm
YM-04108 
						

							
GENERATOR AND STARTER CLUTCH
5-28
EAS4S81014
GENERATOR AND STARTER CLUTCH
Removing the generator and starter clutch
Order Job/Parts to remove Q’ty RemarksSeat Refer to GENERAL CHASSIS on page 4-1.
Fuel tank Refer to FUEL TANK on page 7-1.
Coolant Drain
Refer to CHANGING THE COOLANT on 
page 3-20.
Coolant reservoir tank Refer to RADIATOR on page 6-1.
Engine oil Drain
Refer to CHANGING THE ENGINE OIL on 
page 3-14.
1 Stator coil assembly lead coupler 1 Disconnect.
2 Generator rotor cover 1
3 Generator rotor cover gasket 1
4Dowel pin 2
5 Stator coil assembly lead holder 2
6 Stator coil assembly 1
7 Generator rotor bolt 1
8 Washer 1
9 Generator rotor 1
10 Starter clutch assembly 1 
						

							
GENERATOR AND STARTER CLUTCH
5-29
11 Idler gear shaft 1
12 Idler gear 1
13 Starter clutch drive gear 1For installation, reverse the removal proce-
dure.
Removing the generator and starter clutch
Order Job/Parts to remove Q’ty Remarks