Yamaha F50 Service Manual

							62Y3A115-34
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CAUTION:
Do not turn the sprockets counterclock-
wise, otherwise the valve system may be
damaged.
9. Tighten the driven sprocket bolt 2
 to the
specified torque.
ÈFor USA and Canada
ÉFor worldwide
10. Tighten the drive sprocket nut 6
 to the
specified torque, and then install the
breather hose.
NOTE:
Use a deep socket A
 (M42) for this proce-
dure.Flywheel magnet holder: YB-06139
Flywheel holder: 90890-06522
Driven sprocket bolt 2
:
38 N·m (3.8 kgf·m, 27 ft·lb)
Crankshaft holder B
: YB-06562 
Crankshaft holder 18 B
: 90890-06562
Drive sprocket nut 6
:
140 N·m (14 kgf·m, 100 ft·lb)
Timing belt and sprockets 
						

							POWRPower unit
5-3562Y3A11
Cylinder head5 
						

							62Y3A115-36
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È
 Tightening sequence No. Part name Q’ty RemarksTightening torques
Stage N·mkgf·mft·lb
1 Cylinder head 1
2Oil pump 1
3 Cylinder head cover 1
4Bolt 7 M6 ×
 20 mm
5 Cylinder head cover 
gasket1
Not reusable
6 Bolt 10 M9 ×
 95 mm 1st
2nd23
472.3
4.717
34
7 Spark plug 4 18 1.8 13
8Bolt 5 M6 ×
 25 mm 1st
2nd6
120.6
1.24.3
8.7
9 Dowel pin 2
10 Cylinder head gasket 1
Not reusable
11 Grommet 4
12 Anode 4
13 Cover 4
14 Bolt 4
15 Cover 4
16 Bolt 4
17 O-ring 1
Not reusable
18 O-ring 1Not reusable
19 O-ring 1Not reusable
20 Bolt 4 M6 ×
 40 mm
21 Housing 1
22 Drive shaft 1
23 Pin 1
24 Inner rotor 1
25 Outer rotor 1
26 Gasket 1
Not reusable
27 Cover 1
28 Screw 2 M6 ×
 20 mm
Cylinder head 
						

							POWRPower unit
5-3762Y3A11 
						

							62Y3A115-38
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No. Part name Q’ty RemarksTightening torques
Stage N·mkgf·mft·lb
1 Rocker arm assembly 8
2 Rocker arm shaft 1
3 Cylinder head 1
4 Exhaust valve 4
5 Intake valve 4
6 Camshaft 1
7 Valve cotter 16
8 Spring retainer 8
9 Valve spring 8
10 Spring seat 8
11 Stem seal 8
Not reusable
12 Valve guide 8Not reusable
13 Retaining bolt 1
14 Gasket 1
Not reusable
15 Oil seal 1Not reusable
16 Bolt 5 M8 ×
 22 mm 18 1.8 13
17 Rocker arm retainer 2
18 Tensioner 2
19 Rocker arm retainer 1
20 Stopper guide 2
Cylinder head 
						

							POWRPower unit
5-3962Y3A11
Removing the cylinder head
1. Check that the camshaft dowel pin hole
a
 is in the position shown in the illustra-
tion. Adjust if necessary.
2. Remove the cylinder head cover bolts in
the sequence shown.
3. Remove the cylinder head bolts in the
sequence shown.4. Remove the oil pump 1
, rocker arm
assembly 2
, and rocker arm shaft 3
.
S62Y5260
S62Y5276
23 
						

							62Y3A115-40
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5. Remove the retaining bolt 4
, then the
camshaft 5
 by pulling it downward.
6. Remove the intake valve and exhaust
valves.
NOTE:
When replacing the valve, also replace the
valve guide and stem seal.
Checking the valve springs
1. Measure the valve spring free length a
.
Replace if out of specification.
2. Measure the valve spring tilt b
. Replace
if out of specification.
Checking the valves
1. Check the valve face for pitting or wear.
Replace if necessary.
Valve spring compressor 6
:
YM-01253 / 90890-04019
Valve spring compressor attachment 7
:
90890-06320
Valve spring free length limit a
:
37.85 mm (1.490 in)
Valve spring tilt limit b
: 1.7 mm (0.07 in)
Cylinder head 
						

							POWRPower unit
5-4162Y3A11
2. Measure the valve margin thickness a
.
Replace if out of specification.
3. Measure the valve stem diameter b
.
Replace if out of specification.
4. Measure the valve stem runout. Replace
if out of specification.
Checking the valve guides
1. Measure the valve guide inside diameter
a
. Replace if out of specification.
Replacing the valve guides
1. Remove the valve guide 1
 by striking
the special service tool from the combus-
tion chamber side. Valve margin thickness a
:
Intake: 0.6–1.0 mm (0.024–0.039 in)
Exhaust: 0.7–1.1 mm (0.028–0.043 in)
Valve stem diameter b
:
Intake:
5.48–5.49 mm (0.2157–0.2161 in)
Exhaust:
5.46–5.47 mm (0.2150–0.2153 in)
Valve stem runout:
Intake: 0.03 mm (0.0012 in) 
Exhaust: 0.03 mm (0.0012 in) 
Valve guide inside diameter limit a
:
5.50–5.51 mm (0.2165–0.2169 in)
Valve guide remover: YM-01122
Valve guide remover/installer:
90890-06801 
						

							62Y3A115-42
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2. Install the new valve guide 2
 by striking
the special service tool from the cam-
shaft side until the valve guide clip 3
contacts the cylinder head.
NOTE:
Apply engine oil to the surface of the new
valve guide.
3. Insert the special service tool into the
valve guide 2
, and then ream the valve
guide.
NOTE:
Turn the valve guide reamer clockwise to
ream the valve guide.
Do not turn the reamer counterclockwise
when removing the reamer.4. Measure the valve guide inside diameter.
Replace the valve guide if out of specifi-
cation.
Checking the valve seat 
1. Eliminate carbon deposits from the valve
with a scraper.
2. Apply a thin, even layer of Mechanic’s
blueing dye (Dykem) onto the valve seat.
3. Lap the valve slowly on the valve seat
with a valve lapper (commercially obtain-
able) as shown.
4. Measure the valve seat contact width a
where the blueing dye is adhered to the
valve face. Reface the valve seat if the
valve is not seated properly or if the valve
seat contact width is out of specification.
Replace the valve guide if the valve seat
contact is uneven. Valve guide remover: YM-01122
Valve guide remover/installer:
90890-06801
Valve guide reamer:
YM-01196 / 90890-06804
Valve guide inside diameter:
5.50–5.51 mm (0.2165–0.2169 in)
Cylinder head 
						

							POWRPower unit
5-4362Y3A11
Refacing the valve seat
1. Reface the valve seat with the valve seat
cutter.
2. Cut the surface of the valve seat with a
45° cutter by turning the cutter clockwise
until the valve seat face has become
smooth.
aSlag or rough surface
CAUTION:
Do not over cut the valve seat. Make sure
to turn the cutter evenly downward at a
pressure of 40–50 N (4–5 kgf, 8.8–11 lbf)
to prevent chatter marks.
3. Use a 30° cutter to adjust the contact
width of the top edge of the valve seat.
bPrevious contact width
Valve seat contact width 
a:
Intake: 0.9–1.1 mm (0.035–0.043 in)
Exhaust: 0.9–1.1 mm (0.035–0.043 in)
Valve seat cutter set: YM-91043-C
Valve seat cutter holder: 90890-06316
Valve seat cutter:
30° (intake): 90890-06326
30° (exhaust): 90890-06328
45° (intake and exhaust): 90890-06555
60° (intake): 90890-06323
60° (exhaust): 90890-06315
S62Y5460
30°