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...

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...

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...

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
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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...

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
:...

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...

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....