Yamaha F50 Service Manual

							62Y3A115-54
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È
 Tightening sequence No. Part name Q’ty RemarksTightening torques
Stage N·mkgf·mft·lb
31 Anode 1
32 Cover 1
33 Cover 1
34 Bolt 1 M6 ×
 20 mm
35 Bolt 1 M5 ×
 12 mm
36 Bolt 10 M6 ×
 35 mm 1st
2nd6
120.6
1.24.3
8.7
Cylinder body 
						

							POWRPower unit
5-5562Y3A11
Removing and installing the oil filter
1. Place a rag under the oil filter, and then
remove the filter.
NOTE:
Be sure to clean up any oil spills.
2. Apply a thin coat of the new engine oil to
the O-ring of the new oil filter.
3. Install the oil filter, and then tighten it to
the specified torque.
Disassembling the cylinder body
1. Remove the exhaust cover bolts in the
sequence shown. Oil filter wrench: YU-38411 / 90890-01426
S62Y5690
S62Y5700
E
Oil filter wrench: YU-38411 / 90890-01426
Oil filter: 18 N·m (1.8 kgf·m, 13 ft·lb)
S62Y5710 
						

							62Y3A115-56
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2. Remove the crankcase bolts in the
sequence shown.
3. Remove the connecting rod bolts and the
piston assemblies.
4. Remove the crankshaft, oil seals, and
dowel pins.
5. Remove the piston pin clip 1
 with pliers,
and then remove the piston.
Checking the piston diameter
1. Measure the piston outside diameter at
the specified measuring point. Replace if
out of specification.
Checking the cylinder bore
1. Measure the cylinder bore (D1–D6) a
 at
measuring points b
, c
 and d
, and in
direction e
, which is parallel to the
crankshaft, and direction f
, which is at a
right angle to the crankshaft.
Piston diameter a
:
62.95–62.96 mm (2.478–2.479 in)
Measuring point b
:
5 mm (0.2 in) up from the bottom of the 
piston skirt
Oversize piston diameter:
Oversize 1: +0.25 mm (0.01 in)
Oversize 2: +0.50 mm (0.02 in)
Cylinder bore a
:
63.00–63.01 mm (2.480–2.481 in)
Cylinder body 
						

							POWRPower unit
5-5762Y3A11
2. Calculate the taper limit. Replace or
rebore the cylinder body if out of specifi-
cation.
3. Calculate the out-of-round limit. Replace
or rebore the cylinder body if out of spec-
ification.
Checking the piston clearance
1. Rebore the cylinder or replace the piston
and piston rings as a set or the cylinder
body, or both if out of specification.
Checking the piston rings
1. Check the piston ring 1
 dimensions of B
and T. Replace if out of specification.2. Level the piston ring 1
 in the cylinder
with the piston crown of an inverted pis-
ton.
3. Check the piston ring end gap d
 at the
specified measuring point. Replace if out
of specification. Taper limit = maximum of D
1 or D2 – 
minimum of D
5 or D6:
0.08 mm (0.003 in)
Out-of-round limit = maximum of D
1, D3, or 
D
5 – minimum of D2, D4, or D6:
0.05 mm (0.002 in)
Piston clearance:
0.04–0.06 mm (0.0016–0.0024 in)
Piston ring dimensions:
Top ring a
:
B: 1.17–1.19 mm (0.046–0.047 in)
T: 2.39–2.41 mm (0.094–0.095 in)
Second ring b
:
B: 1.47–1.49 mm (0.058–0.059 in)
T: 2.49–2.51 mm (0.098–0.099 in)
Oil ring c
:
B: 2.34–2.46 mm (0.092–0.097 in)
T: 2.75 mm (0.108 in)
Piston ring end gap d
:
Top ring: 0.15–0.30 mm (0.006–0.012 in)
Second ring:
0.30–0.50 mm (0.012–0.020 in)
Oil ring: 0.20–0.70 mm (0.008–0.028 in)
Measuring point e
: 20 mm (0.8 in)
S62Y5780
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							62Y3A115-58
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Checking the piston ring grooves
1. Measure the piston ring grooves.
Replace the piston if out of specification.
Checking the piston ring side 
clearance
1. Measure the piston ring side clearance.
Replace the piston and piston rings as a
set if out of specification.
Checking the piston pin boss bore
1. Measure the piston pin boss bore.
Replace the piston if out of specification.
Checking the piston pin
1. Measure the piston pin diameter.
Replace if out of specification. Piston ring groove:
Top ring a
:
1.23–1.25 mm (0.048–0.049 in)
Second ring b
:
1.52–1.54 mm (0.060–0.061 in)
Oil ring c
:
2.51–2.53 mm (0.099–0.100 in)
Piston ring side clearance:
Top ring a
:
0.04–0.08 mm (0.002–0.003 in)
Second ring b
:
0.03–0.07 mm (0.001–0.003 in)
Oil ring c
:
0.05–0.19 mm (0.002–0.007 in)
Piston pin boss bore:
15.974–15.985 mm (0.6289–0.6293 in)
Piston pin diameter:
15.965–15.970 mm (0.6285–0.6287 in)
Cylinder body 
						

							POWRPower unit
5-5962Y3A11
Checking the connecting rod small 
end inside diameter
1. Measure the connecting rod small end
inside diameter a
. Replace the connect-
ing rod if out of specification.
Checking the connecting rod big end 
side clearance
1. Measure the connecting rod big end side
clearance a
. Replace the connecting
rod or crankshaft, or both if out of specifi-
cation.
Checking the connecting rod bolt
1. Measure the connecting rod bolt thread
diameter at the two points a
 and b
. 
2. Calculate the difference between a
 and
b
. Replace if out of specification.
Checking the crankshaft
1. Measure the crankshaft journal diameter
a
, crank pin diameter b
, and crank pin
width c
. Replace the crankshaft if out of
specification. Connecting rod small end inside diameter 
a
: 15.985–15.998 mm (0.6293–0.6298 in)
Connecting rod big end side clearance a
:
0.05–0.22 mm (0.002–0.009 in)
S62Y5840
Connecting rod bolt thread diameter limit 
(difference between a
 and b
):
0–0.1 mm (0–0.004 in)
Crankshaft journal diameter a
:
42.984–43.000 mm (1.6923–1.6929 in)
Crank pin diameter b
:
32.984–33.000 mm (1.2986–1.2992 in)
Crank pin width c
:
21.000–21.070 mm (0.8268–0.8295 in)
S62Y5850
5 mm (0.2 in)
10 mm (0.4 in) 
						

							62Y3A115-60
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2. Measure the crankshaft runout. Replace
the crankshaft if out of specification.
Checking the crankshaft main 
journal oil clearance
1. Clean the bearings, main journals, and
bearing portions of the crankcase and
cylinder body.
2. Place the cylinder body upside down on
a bench.
3. Install half of the bearings 1
 and the
crankshaft 2
 into the cylinder body 3
.
CAUTION:
Install the bearings in their original posi-
tions.
NOTE:
Insert the projection a
 of the bearing into the
notch in the cylinder body.
4. Put a piece of Plastigauge
® (PG-1) on
each main journal parallel to the crank-
shaft.
NOTE:
Do not put the Plastigauge (PG-1) over the
oil hole in the main journals of the crankshaft.
5. Install the remaining half of the bearings
into the crankcase.
NOTE:
Insert the projection of the bearing into the
notch in the crankcase.
6. Install the crankcase onto the cylinder
body and apply engine oil onto the
threads of the crankcase bolts.
7. Tighten the crankcase bolts to the speci-
fied torques in two stages and in the
sequence shown. Crankshaft runout limit:
0.04 mm (0.0016 in)
Cylinder body 
						

							POWRPower unit
5-6162Y3A11
NOTE:
Do not move the crankshaft until the main
journal oil clearance measurement has been
completed.
8. Remove the crankcase and measure the
width of the compressed Plastigauge
(PG-1) on each main journal. Replace
the main bearing if out of specification.
Checking the crankshaft pin oil 
clearance
1. Clean the bearings and the connecting
rod.
2. Install the upper half of the bearing into
the connecting rod 1
 and the lower half
into the connecting rod cap 2
.
CAUTION:
Install the bearings in their original posi-
tions.
NOTE:
Insert the projection a
 of the bearing into the
slot on the cap and connecting rod.
3. Put a piece of Plastigauge (PG-1) onto
the crank pin, parallel to the crankshaft.
NOTE:
Be sure not to put the Plastigauge (PG-1)
over the oil hole in the crank pin of the crank-
shaft.
4. Install the connecting rod to the crank pin
3
. Crankcase bolt (M8):
1st: 15 N·m (1.5 kgf·m, 11 ft·lb)
2nd: 30 N·m (3.0 kgf·m, 22 ft·lb)
Crankcase 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)
Crankshaft main journal oil clearance:
0.012–0.036 mm (0.0005–0.0014 in) 
						

							62Y3A115-62
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NOTE:
Align the alignment marks b
 on the con-
necting rod cap and connecting rod.
Face the embossed “Y” mark on the con-
necting rod toward the flywheel side of the
crankshaft.
5. Tighten the connecting rod bolts to the
specified torques in two stages.
NOTE:
Do not turn the connecting rod until the crank
pin oil clearance measurement has been
completed.
6. Remove the connecting rod cap and
measure the width of the compressed
Plastigauge (PG-1) on each crank pin.
Replace the connecting rod bearing if out
of specification.
Selecting the crankshaft main 
journal bearing
1. When replacing the main bearing, select
the suitable bearing as follows.
2. Check the crankshaft journal mark on the
crankshaft 1
 and the cylinder body mark
on the cylinder body 2
.
3. Select the suitable color a
 for the main
bearing from the table.
Connecting rod bolt:
1st: 6 N·m (0.6 kgf·m, 4.3 ft·lb)
2nd: 17 N·m (1.7 kgf·m, 12 ft·lb)
Crank pin oil clearance:
0.016–0.040 mm (0.0006–0.0015 in)
Cylinder 
body markCrankshaft 
journal markBearing 
color
AAYellow
AB
Red
BA
BB
Pink
CA
C B Green
Cylinder body 
						

							POWRPower unit
5-6362Y3A11
4. When installing the main bearing, insert
the projection of the main bearing into
the slot on the cylinder body.
CAUTION:
Remove any small metal particles and oil
from the contact surfaces of the cylinder
body and the main bearing.
5. Measure the main journal oil clearance
with a piece of Plastigauge (PG-1).
6. If the oil clearance is below specification,
check the main bearing color and clean
the contact surface of the cylinder body
and the main bearing, and then check
the main journal oil clearance again.
7. If the oil clearance is over specification,
install an oversized main bearing, and
then check the main journal oil clearance
again.
Selecting the connecting rod big end 
bearing
1. When replacing the connecting rod bear-
ing, select the suitable connecting rod
bearing as follows.
2. Check the crank pin mark on the crank-
shaft 1
 and the connecting rod cap mark
or painted color on the connecting rod 2
.
3. Select the suitable color a
 for the con-
necting rod bearing from the table.4. When installing the connecting rod bear-
ing, insert the projection of the connect-
ing rod bearing into the slot on the
connecting rod.
CAUTION:
Remove any small metal particles and oil
from the contact surfaces of the connect-
ing rod and the connecting rod bearing.
5. Measure the crank pin oil clearance with
a piece of Plastigauge (PG-1). Crankshaft main journal oil clearance:
0.012–0.036 mm (0.0005–0.0014 in)
Connecting 
rod cap 
mark/colorCrank pin 
markBearing 
color
I
/Red A Yellow
I
/Red B
Red
II
/Blue A
II
/Blue B
Pink
III
/Yellow A
III
/Yellow B Green
Crank pin oil clearance:
0.016–0.040 mm (0.0006–0.0015 in)