Yamaha YFM660 01 User Manual

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ENGCAMSHAFT AND CYLINDER HEAD
3.Measure:

Cylinder head warpage
Out of specification →
 Resurface.
***********************************************
Warpage measurement and resurfacing
steps:

Place a straightedge and a feeler gauge
across the cylinder head.

Use a feeler gauge to measure the warpage.

If the warpage is out of specification, resur-
face the cylinder head.

Place a 400 ~ 600 grit wet sandpaper on the
surface plate, and resurface the head using
a figure-eight sanding pattern.
NOTE:
To ensure an even surface rotate the cylinder
head several times.
***********************************************
Cylinder head warpage:
Less than 0.05 mm (0.002 in)
INSTALLING THE CAMSHAFT AND CYLIN-
DER HEAD
1.Install:

Cylinder head

Bolts (M9 : 1 ~ 6)

Bolt (M6 : 7)
NOTE:

Tighten the bolts in the proper sequence.

Follow the numerical order shown in the illus-
tration. Tighten the bolts in two stages.
T R..38 Nm (3.8 m · kg, 27 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb) 
						

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ENGCAMSHAFT AND CYLINDER HEAD
2.Install:

Camshaft

Camshaft sprocket
***********************************************
Installation steps:

Turn the crankshaft counterclockwise with a
wrench.

Align the “I” mark 1
 on the rotor with the sta-
tionary pointer 2
 on the crankcase cover.
When the “I” mark is aligned with the station-
ary pointer, the piston is at the Top Dead
Center (T.D.C.).
CAUTION:
Do not turn the crankshaft during the cam-
shaft installation.

Temporarily install the camshaft sprocket on
the camshaft. (Do not install the bolts.) Then,
install the timing chain on the camshaft
sprocket.
NOTE:
Make sure the small holes 3
 on the camshaft
face upward.

Align the notches 4
 on the decompressor
cams with the projections 5
 on the decom-
pressor spring lever, then install the cam-
shaft sprocket on the camshaft.
NOTE:
Check that each part is positioned as shown in
the illustration.
6Small holes on camshaft sprocket
7Punch mark on decompressor spring lever
8Top front of cylinder head 
						

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ENGCAMSHAFT AND CYLINDER HEAD

Install the decompressor cam guide plates 9
and camshaft sprocket bolts 0
.

Remove the retaining wire.
***********************************************
T R..
Camshaft sprocket bolt:
20 Nm (2.0 m  kg, 14 ft  lb)
3.Install:

Timing chain tensioner
***********************************************
Installation steps:

Remove the timing chain tensioner cap bolt
1
, washer 2
 and spring 3
.

Release the timing chain tensioner one-way
cam 4
 and push the tensioner rod 5
 all the
way in.

Install the tensioner 6
 with a new gasket into
the cylinder.
WARNING
Always use a new gasket.

Install the spring, washer and timing chain
tensioner cap bolt.
***********************************************
4.Check:

Small holes on camshaft sprocket

Rotor “I” mark
Out of alignment →
 Adjust.
T R..
Bolts (timing chain tensioner):
10 Nm (1.0 m  kg, 7.2 ft  lb)
T R..
Timing chain tensioner cap bolt:
22 Nm (2.2 m  kg, 16 ft  lb) 
						

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ENGVALVES AND VALVE SPRINGS
VALVES AND VALVE SPRINGS
Order Job name/Part name Q’ty Remarks
Removing the valve and valve 
springRemove the parts in the order below.
Cylinder head Refer to “CAMSHAFT AND CYLINDER
HEAD”.
1 Valve cotter 10
Refer to “REMOVING/INSTALLING THE 
VALVE AND VALVE SPRING”. 2 Valve spring retainer 5
3 Intake valve spring 3
4 Exhaust valve spring 2
5 Intake valve 3
6 Exhaust valve 2
7 Valve stem seal 5
8 Valve spring seat 5
For installation, reverse the removal pro-
cedure. 
						

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ENGVALVES AND VALVE SPRINGS
REMOVING THE VALVE AND VALVE 
SPRING
1.Check:

Valve sealing
Leakage at the valve seat →
 Inspect the
valve face, valve seat and valve seat width.
Refer to “VALVE AND VALVE SPRING
INSPECTION”.
***********************************************
Checking steps:

Pour a clean solvent 1
 into the intake and
exhaust ports.

Check that the valve seals properly.
There should be no leakage at the valve seat
2
.
***********************************************
2.Remove:

Valve cotters
NOTE:
Attach a valve spring compressor 1
 and
attachment 2
 between the valve spring
retainer and the cylinder head to remove the
valve cotters.
Valve spring compressor:
P/N. YM-04019, 90890-04019
Valve spring compressor 
attachment:
P/N. 90890-01243 
						

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ENGVALVES AND VALVE SPRINGS
CHECKING THE VALVE AND VALVE 
SPRING
1.Measure:

Stem-to-guide clearance
Out of specification →
 Replace the valve
guide.Stem-to-guide clearance =
valve guide inside diameter a –
valve stem diameter b 
Clearance (stem to guide):
Intake:
0.010 ~ 0.037 mm
(0.0004 ~ 0.0015 in)
: 0.08 mm (0.0031 in)
Exhaust:
0.025 ~ 0.052 mm
(0.0010 ~ 0.0020 in)
: 0.10 mm (0.0039 in)
2.Replace:

Valve guide
***********************************************
Replacement steps:
NOTE:
To ease guide removal, installation and to
maintain correct fit, heat the cylinder head to
100 °C (212 °F) in an oven.

Remove the valve guide using a valve guide
remover 1
.

Install the new valve guide using a valve
guide remover 1
 and valve guide installer
2
.

After installing the valve guide, bore the
valve guide using a valve guide reamer 3
 to
obtain proper stem-to-guide clearance.
NOTE:
After replacing the valve guide reface the valve
seat.
***********************************************
Valve guide remover (ø 6):
P/N. YM-4064-A, 90890-04064
Valve guide installer (ø 6):
P/N. YM-04065-A, 90890-04065
Valve guide reamer (ø 6):
P/N. YM-04066, 90890-04066 
						

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ENGVALVES AND VALVE SPRINGS
3.Check:

Valve face
Pitting/wear →
 Grind the face.

Valve stem end
Mushroom shape or diameter larger than the
body of the stem →
 Replace.
4.Measure:

Margin thickness a
 
Out of specification →
 Replace.
Margin thickness:
Intake:
0.85 ~ 1.15 mm 
(0.0335 ~ 0.0453 in)
Exhaust:
0.85 ~ 1.15 mm 
(0.0335 ~ 0.0453 in)
5.Measure:

Runout (valve stem)
Out of specification →
 Replace.
NOTE:

When installing a new valve always replace
the guide.

If the valve is removed or replaced always
replace the oil seal.
6.Eliminate:

Carbon deposits
(from the valve face and valve seat)
7.Check:

Valve seats
Pitting/wear →
 Reface the valve seat.
Runout limit:
0.01 mm (0.0004 in) 
						

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ENGVALVES AND VALVE SPRINGS
8.Measure:

Valve seat width a
 
Out of specification →
 Reface the valve seat.
***********************************************
Measurement steps:

Apply Mechanic’s blueing dye (Dykem) b
 to
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 pattern.

Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.

If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat must
be refaced.
***********************************************
Valve seat width:
Intake:
0.9 ~ 1.1 mm 
(0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm
(0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
9.Lap:

Valve face

Valve seat
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
***********************************************
Lapping steps:

Apply a coarse lapping compound to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.

Apply molybdenum disulfide oil to the valve
stem. 
						

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ENGVALVES AND VALVE SPRINGS

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 compound.
NOTE:
For 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.
NOTE:
After every lapping operation be sure to clean
off all of the compound from the valve face and
valve seat.

Apply Mechanic’s blueing dye (Dykem) to 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 pattern.

Measure the valve seat width again. If the
valve seat width is out of specification, reface
and relap the valve seat.
***********************************************
10.Measure:

Valve spring free length a
 
Out of specification →
 Replace.
Free length (valve spring):
Inner:
35.95 mm (1.42 in)
: 34.15 mm (1.34 in)
Outer:
37.75 mm (1.49 in)
: 35.86 mm (1.41 in) 
						

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ENGVALVES AND VALVE SPRINGS
11.Measure:

Compressed spring force a
 
Out of specification →
 Replace.
b
Installed length
Compressed spring force:
Inner:
149 ~ 173 N at 27.2 mm
(15.19 ~ 17.64 kg, 
33.50 ~ 38.89 lb at 1.07 in)
Outer:
165 ~ 191 N at 30.7 mm
(16.83 ~ 19.49 kg, 
37.09 ~ 42.94 lb at 1.21 in)
12.Measure:

Spring tilt a
 
Out of specification →
 Replace.
Spring tilt limit:
Inner:
2.5°/1.6 mm (0.06 in)
Outer:
2.5°/1.6 mm (0.06 in)
INSTALLING THE VALVE AND VALVE 
SPRING
1.Apply:

Molybdenum disulfide oil
(onto the valve stem and valve stem seal)
2.Install:

Valve spring seats

Valve stem seals

Valves

Valve springs

Valve spring retainers
NOTE:
Install the valve springs with the larger pitch a
facing upwards.
b
Smaller pitch
New