Yamaha F50 Service Manual

							62Y3A115-44
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4. Use a 60° cutter to adjust the contact
width of the bottom edge of the valve
seat.
bPrevious contact width
5. Use a 45° cutter to adjust the contact
width of the valve seat to specification.
bPrevious contact width
cSpecified contact width
6. If the valve seat contact area is too wide
and situated in the center of the valve
face, use a 30° cutter to cut the top edge
of the valve seat, a 60° cutter to cut the
bottom edge to center the area and set
its width.
bPrevious contact width
7. If the valve seat contact area is too nar-
row and situated near the top edge of the
valve face, use a 30° cutter to cut the top
edge of the valve seat. If necessary, use
a 45° cutter to center the area and set its
width.
bPrevious contact width
8. If the valve seat contact area is too nar-
row and situated near the bottom edge of
the valve face, use a 60° cutter to cut the
bottom edge of the valve seat. If neces-
sary, use a 45° cutter to center the area
and set its width.
bPrevious contact width
9. Apply a thin, even layer of lapping com-
pound onto the valve seat, and then lap
the valve using a valve lapper (commer-
cially obtainable).
S62Y5461
60°
S62Y5462
45°
Cylinder head 
						

							POWRPower unit
5-4562Y3A11
CAUTION:
Do not get the lapping compound on the
valve stem and valve guide.
10. After every lapping procedure, be sure to
clean off any remaining lapping com-
pound from the cylinder head and the
valve.
11. Check the valve seat contact area of the
valve again.
Checking the rocker arms and rocker 
arm shaft
1. Check the rocker arms, rocker arm shaft,
and rocker arm contact surface a
 for
wear. Replace if necessary.
2. Measure the rocker arms inside diameter
b
 and rocker arm shaft outside diameter
c
. Replace if out of specification.
Checking the camshaft
1. Measure the cam lobe. Replace if out of
specification.2. Measure the camshaft runout. Replace if
out of specification.
Rocker arm inside diameter b
:
16.00–16.01 mm (0.6299–0.6303 in)
Rocker arm shaft outside diameter c
:
15.98–15.99 mm (0.6291–0.6295 in)
Cam lobe a
:
Intake:
30.89–30.99 mm (1.2161–1.2200 in)
Exhaust:
30.82–30.92 mm (1.2135–1.2175 in)
Cam lobe b
:
Intake:
25.95–26.05 mm (1.0217–1.0256 in)
Exhaust:
25.95–26.05 mm (1.0217–1.0256 in)
Camshaft runout limit: 0.04 mm (0.0016 in) 
						

							62Y3A115-46
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3. Measure the camshaft journal diameter
c
 and cylinder head journal inside diam-
eter d
. Replace the camshaft and cylin-
der head if out of specification.
4. Calculate the camshaft oil clearance e
as follows. Replace the camshaft and
cylinder head as a set if out of specifica-
tion.
Checking the cylinder head
1. Eliminate carbon deposits from the com-
bustion chambers and check for deterio-
ration.
2. Check the cylinder head warpage using a
straightedge 1
 and thickness gauge 2
in five directions as shown. Replace if out
of specification. Camshaft journal diameter c
:
#1: 36.93–36.94 mm (1.4539–1.4543 in)
#2, #3, #4:
36.94–36.95 mm (1.4543–1.4547 in)
Cylinder head journal inside diameter d
:
37.00–37.02 mm (1.4567–1.4575 in)
e
 = d
 – c
:
#1: 0.06–0.09 mm (0.0024–0.0035 in)
#2, #3, #4:
0.05–0.08 mm (0.0018–0.0031 in)
Cylinder head warpage limit:
0.1 mm (0.004 in)
Cylinder head 
						

							POWRPower unit
5-4762Y3A11
Checking the oil pump
1. Measure the oil pump rotor clearances
as shown. Replace if out of specification.
Installing the valves
1. Install the new valve stem seal 1
 to the
valve guide, and then apply engine oil to
the valve guide.2. Install the valve 2
, spring seat 3
, valve
spring 4
, and spring retainer 5
 in the
sequence shown, and then attach the
special service tool.
NOTE:
Face the fine pitch side a
 of the valve spring
toward the spring seat. Clearance a
:
0.09–0.15 mm (0.004–0.006 in)
Clearance b
:
0.01–0.10 mm (0.0004–0.0039 in)
Clearance c
:
0.03–0.08 mm (0.001–0.003 in)
Valve spring compressor 6
:
YM-01253 / 90890-04019
Valve spring compressor attachment 7
:
90890-06320
S62Y5590
E
1 
						

							62Y3A115-48
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3. Compress the valve spring, and then
install the valve cotter 8
 using a thin
screwdriver with a small amount of
grease applied to it.
4. Lightly tap the spring retainer with a plas-
tic hammer to set the valve cotter
securely.Installing the camshaft
1. Install the new oil seal 1
.
ÈFor USA and Canada
ÉFor worldwide
2. Install the camshaft 2
 in the direction
shown, then the retaining bolt 3
.
Drive shaft needle bearing depth stop:
YB-34473 
Bearing outer race attachment:
90890-06626 
S62Y5630
1
Cylinder head 
						

							POWRPower unit
5-4962Y3A11
Installing the rocker arm assembly
1. Check that the camshaft dowel pin hole
a
 is in the position shown in the illustra-
tion. Adjust if necessary.
2. Assembly the rocker arm 1
 and rocker
arm shaft 2
, and the tensioner 3
, rocker
arm retainer 4
, stopper guide 5
 by
installing the bolts.
NOTE:
Make sure that the arrow marks b
 on the two
tensioners and stopper guides are facing up.3. Install the rocker arm shaft assembly to
the cylinder head by installing the bolts,
and then tighten them to the specified
torque.
Installing the cylinder head
1. Install the oil pump 1
 by aligning the oil
pump drive shaft a
 with the camshaft pin
b
.
S62Y5650
a
Bolt: 18 N·m (1.8 kgf·m, 13 ft·lb)
S62Y5665R 
						

							62Y3A115-50
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2. Tighten the cylinder head bolts to the
specified torques in two stages and in the
sequence shown.
NOTE:
Apply engine oil to the cylinder head bolts
(M9) before installation.
3. Tighten the cylinder head cover bolts in
the sequence shown. Cylinder head bolt (M9):
1st: 23 N·m (2.3 kgf·m, 17 ft·lb)
2nd: 47 N·m (4.7 kgf·m, 34 ft·lb)
Cylinder head bolt (M6):
1st: 6 N·m (0.6 kgf·m, 4.3 ft·lb)
2nd: 12 N·m (1.2 kgf·m, 8.7 ft·lb)
Cylinder head 
						

							POWRPower unit
5-5162Y3A11
Cylinder body5 
						

							62Y3A115-52
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No. Part name Q’ty RemarksTightening torques
Stage N·mkgf·mft·lb
1 Oil filter 1 18 1.8 13
2 Crankshaft 1
3 Bolt 10 M8 ×
 82 mm 1st
2nd15
301.5
3.011
22
4 Bolt 10 M6 ×
 35 mm 1st
2nd6
120.6
1.24.3
8.7
5 Crankcase 1
6 Oil seal 1
Not reusable
7 Main bearing 10
8 Oil seal 1
Not reusable
9 Connecting rod bearing 8
10 Connecting rod cap 4
11 Bolt 8 1st
2nd6
170.6
1.74.3
12
12 Dowel pin 2
13 Cylinder body 1
14 Connecting rod 1
15 Piston pin clip 2
Not reusable
16 Piston pin 1
17 Piston 1
18 Oil ring 1
19 Second ring 1
20 Top ring 1
21 Piston assembly 1
22 Gasket 1
Not reusable
23 Exhaust cover 1
24 Thermostat 1
25 Gasket 1
Not reusable
26 Cover 1
27 Bolt 2 M6 ×
 35 mm
28 Clamp 1
29 Bolt 10
30 Grommet 1
Cylinder body 
						

							POWRPower unit
5-5362Y3A11