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...

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...

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...

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...

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:...

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...

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...

POWRPower unit
5-5362Y3A11