Yamaha Fz6 N Service Manual

							
CRANKSHAFT
5-60
EAS25950
CRANKSHAFT
Removing the connecting rods and pistons
Order Job/Parts to remove Q’ty RemarksLower crankcase Refer to CRANKCASE on page 5-55.
1 Connecting rod cap 4
2 Big end lower bearing 4
3 Big end upper bearing 4
4 Piston pin clip 8
5 Piston pin 4
6Piston 4
7 Connecting rod 4
8 Top ring 4
9 2nd ring 4
10 Oil ring 4 For installation, reverse the removal proce-
dure. 
						

							
CRANKSHAFT
5-61
Removing the crankshaft
Order Job/Parts to remove Q’ty RemarksCrankcase Separate.
Refer to CRANKCASE on page 5-55.
Connecting rods caps Refer to CRANKSHAFT on page 5-60.
1Crankshaft 1
2 Crankshaft journal lower bearing 5
3 Crankshaft journal upper bearing 5 For installation, reverse the removal proce-
dure. 
						

							
CRANKSHAFT
5-62
EAS26030
REMOVING THE CONNECTING RODS AND 
PISTONS
The following procedure applies to all of the 
connecting rods and pistons.
1. Remove: Connecting rod cap “1”
 Big end bearings
NOTE:
Identify the position of each big end bearing so 
that it can be reinstalled in its original place.
2. Remove: Piston pin clips “1”
 Piston pin “2”
Piston “3”
CAUTION:
ECA4S81024
Do not use a hammer to drive the piston 
pin out.
NOTE:
 For reference during installation, put identifi-
cation marks on the piston crown.
 Before removing the piston pin, deburr the  piston pin clip groove and the piston pin bore 
area. If both areas are deburred and the pis-
ton pin is still difficult to remove, remove it 
with the piston pin puller set “4”. 3. Remove:
Top ring
 2nd ring
Oil ring
NOTE:
When removing a piston ring, open the end 
gap with your fingers and lift the other side of 
the ring over the piston crown.
EAS25980
REMOVING THE CRANKSHAFT ASSEMBLY
1. Remove: Crankshaft assembly
 Crankshaft journal upper bearings
(from the upper crankcase)
Refer to CRANKSHAFT on page 5-60.
NOTE:
Identify the position of each crankshaft journal 
upper bearing so that it can be reinstalled in its 
original place.
Piston pin puller set90890-01304
Piston pin puller YU-01304 
						

							
CRANKSHAFT
5-63
EAS24390
CHECKING THE CYLINDER AND PISTON
1. Check: Piston wall
 Cylinder wall
Vertical scratches  → Replace the cylinder, 
and replace the piston and piston rings as 
a set.
2. Measure:  Piston-to-cylinder clearance
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a. Measure cylinder bore “C” with the cylinder  bore gauge.
NOTE:
Measure cylinder bore “C” by taking side-to-
side and front-to-back measurements of the 
cylinder. Then, find the average of the mea-
surements.
b. If out of specification, replace the cylinder, 
and replace the piston and piston rings as 
a set.
c. Measure piston skirt diameter “P” with the 
micrometer. d. If out of specification, replace the piston 
and piston rings as a set.
e. Calculate the piston-to-cylinder clearance  with the following formula.
f. If out of specification, replace the cylinder,  and the piston and piston rings as a set.
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EAS24430
CHECKING THE PISTON RINGS
1. Measure: Piston ring side clearance
Out of specification  → Replace the piston 
and piston rings as a set.
NOTE:
Before measuring the piston ring side clear-
ance, eliminate any carbon deposits from the 
piston ring grooves and piston rings.
Bore 65.500–65.510 mm (2.5787–
2.5791 in)
Wear limit 65.56 mm (2.5811 in)
Taper limit
0.050 mm (0.0020 in)
Out of round limit 0.050 mm (0.0020 in)
“C” = maximum of D
1–D6
“T” = maximum of D1 or D2 - maximum of D5 
or D
6
“R” = maximum of D1, D3 or D5 - minimum of 
D
2, D4 or D6
Piston size “P” Standard65.475–65.490 mm (2.5778–
2.5783 in)
a. 4 mm (0.16 in) from the bottom edge of the  piston
 Piston-to-cylinder clearance =
Cylinder bore “C” -
Piston skirt diameter “P”
Piston-to-cylinder clearance 0.010–0.035 mm (0.0004–
0.0014 in)
Limit 0.05 mm (0.0020 in) 
						

							
CRANKSHAFT
5-64
2. Install: Piston ring (into the cylinder)
NOTE:
Level the piston ring into the cylinder with the 
piston crown.
3. Measure: Piston ring end gap Out of specification  → Replace the piston 
ring.
NOTE:
The oil ring expander spacer’s end gap cannot 
be measured. If the oil ring rail’s gap is exces-
sive, replace all three piston rings.
EAS24440
CHECKING THE PISTON PINS
The following procedure applies to all of the 
piston pins.
1. Check:  Piston pin
Blue discoloration/grooves  → Replace the 
piston pin and then check the lubrication 
system.
2. Measure:  Piston pin outside diameter “a” Out of specification  → Replace the piston 
pin.
3. Measure:  Piston pin bore inside diameter “b”
Out of specification  → Replace the piston.
Top ring
Ring side clearance0.030–0.065 mm (0.0012–
0.0026 in)
Limit 0.115 mm (0.0045 in)
2nd ring Ring side clearance0.030–0.065 mm (0.0012–
0.0026 in)
Limit 0.125 mm (0.0049 in)
a. 5 mm (0.20 in)
Top ring
End gap (installed)0.25–0.35 mm (0.0098–0.0138
in)
Limit 0.60 mm (0.0236 in)
2nd ring End gap (installed)0.70–0.80 mm (0.0276–0.0315
in)
Limit 1.15 mm (0.0453 in)
Oil ling End gap (installed)0.10–0.35 mm (0.0039–0.0138
in)
Piston pin outside diameter
15.991–16.000 mm (0.6296–
0.6299 in)
Limit
15.971 mm (0.6288 in) 
						

							
CRANKSHAFT
5-65
4. Calculate: Piston-pin-to-piston-pin-bore clearance Out of specification  → Replace the piston 
pin and piston as a set.
EAS4S81037
CHECKING THE BIG END BEARINGS
1. Measure:  Crankshaft-pin-to-big-end-bearing clear-
ance
Out of specification  → Replace the big end 
bearings.
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The following procedure applies to all of the 
connecting rods.
CAUTION:
ECA4S81025
Do not interchange the big end bearings 
and connecting rods. To obtain the correct 
crankshaft-pin-to-big-end-bearing clear-
ance and prevent engine damage, the big  end bearings must be installed in their orig-
inal positions.
a. Clean the big end bearings, crankshaft 
pins, and the inside of the connecting rod 
halves.
b. Install the big end upper bearing into the  connecting rod and the big end lower bear-
ing into the connecting rod cap.
NOTE:
Align the projections “a” on the big end bear-
ings with the notches “b” in the connecting rod 
and connecting rod cap.
c. Put a piece of Plastigauge
® “1” on the 
crankshaft pin.
d. Assemble the connecting rod halves.
NOTE:
 Do not move the connecting rod or crank- shaft until the clearance measurement has 
been completed.
 Lubricate the bolt threads and seats with 
molybdenum disulfide grease.
 Make sure that the “Y” mark “c” on the con- necting rod faces towards the left side of the 
crankshaft.
 Make sure that the characters “d” on both the  connecting rod and connecting rod cap are 
aligned.
Piston pin bore inside diameter
16.002–16.013 mm (0.6300–
0.6304 in)
Limit 16.043 mm (0.6316 in)
 Piston-pin-to-piston-pin-bore clearance = Piston pin bore diameter “b” -
Piston pin outside diameter “a”
Piston-pin-to-piston-pin-bore
clearance 0.002–0.022 mm (0.0001–
0.0009 in)
Limit 0.072 mm (0.0028 in)
Crankshaft-pin-to-big-end-bear-
ing clearance
0.038–0.062 mm 
(0.0015–0.0024 in) 
						

							
CRANKSHAFT
5-66
e. Tighten the connecting rod bolts.
NOTE:
Install by carrying out the following procedures 
in order to assemble in the most suitable con-
dition. Connecting rod bolts
f. Replace the connecting rod bolts with new  ones.
g. Clean the connecting rod bolts.
h. After installing the big end bearing, assem- ble the connecting rod and connecting rod 
cap once using a single  unit of the connect-
ing rod.
i. Tighten the connecting rod bolt while 
checking that the sections shown “a” and 
“b” are flush with each other by touching 
the surface.
 Side machined face “a”
 Thrusting faces (4 places at front and rear)  “b”
NOTE:
To install the big end bearing, care should be 
taken not to install it at an angle and the posi-
tion should not be out of alignment. j. Loosen the connecting rod bolt, remove the 
connecting rod and connecting rod cap and 
install these parts to the crankshaft with the 
big end bearing kept in the current condi-
tion.
k. Tighten the connecting rod bolts.
CAUTION:
ECA4S81026
Tighten the connecting rod bolts using the 
plastic-region tightening angle method.
Always install new bolts.
l. Clean the connecting rod bolts.
m. Tighten the connecting rod bolts.
n. Put a mark “1” on the corner of the con- necting rod bolt “2” and the connecting rod 
cap “3”
o. Tighten the bolt further to reach the speci- fied angle (120 °).
Connecting rod bolt
24.5 Nm (2.5 m·kg, 17.7 ft·lb)
Connecting rod bolt15 Nm (1.5 m·kg, 11 ft·lb) + 120 ° 
						

							
CRANKSHAFT
5-67
p. After the installation, check that the section show “a” is flush with each other by touch-
ing the surface.
 Side machined face “a”
WARNING
EWA4S81014
 When the bolt is tightened more than the  specified angle, do not loosen the bolt 
and then retighten it.
Replace the bolt with a new one and per-
form the procedure again.
 If they are not flush with each other,  remove the connecting rod bolt and big 
end bearing and restart from step (e). In 
this case, make sure to replace the con-
necting rod bolt.
CAUTION:
ECA4S81027
 Do not use a torque wrench to tighten the nut to the specified angle.
 Tighten the bolt until it is at the specified 
angles.
q. Remove the connecting rod and big end  bearings.
Refer to REMOVING THE CONNECTING 
RODS AND PISTONS on page 5-62.
r. Measure the compressed Plastigauge
® 
width on the crankshaft pin. If the crankshaft-pin-to-big-end-bearing 
clearance is out of specification, select 
replacement big end bearings.
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2. Select:
 Big end bearings (P1–P4)
NOTE:
 The numbers “A” stamped into the crank-shaft web and the numbers “1” on the con-
necting rods are used to determine the 
replacement big end bearing sizes.
 “P1”–“P4” refer to the bearings shown in the 
crankshaft illustration.
For example, if the connecting rod “P
1” and 
the crankshaft web “P
1” numbers are “5” 
and “2” respectively, then the bearing size 
for “P
1” is:
P1 (connecting rod) – P1 
(crankshaft web) =
5 – 2 = 3 (brown)
COLOR CODE
1Blue
2Black
3Brown
4 Green 
						

							
CRANKSHAFT
5-68
EAS26190
INSTALLING THE CONNECTING ROD AND 
PISTON
The following procedure applies to all of the 
connecting rods and pistons.
1. Install: Top ring “1”
 2nd ring “2”
 Upper oil ring rail “3”
 Oil ring expander “4”
 Lower oil ring rail “5”
NOTE:
Be sure to install the piston rings so that the 
manufacturer’s marks or numbers “a” face up.
2. Install:
Piston “1” (onto the respective connecting rod “2”)
 Piston pin “3”
 Piston pin clip “4” 
NOTE:
 Apply engine oil onto the piston pin.  Make sure that the “Y” mark “a” on the con-
necting rod faces left when the arrow mark 
“b” on the piston is pointing up as shown.
 Reinstall each piston into its original cylinder  (numbering order starting from the left: #1 to 
#4).
3. Lubricate: Piston
 Piston rings
 Cylinder (with the recommended lubricant)
4. Offset:  Piston ring end gaps
5. Lubricate:  Crankshaft pins
 Big end bearings
 Connecting rod big end inner surface (with the recommended lubricant)
New
Recommended lubricant
Engine oil
a. Top ring
b. Lower oil ring rail
c. Upper oil ring rail
d. 2nd ring
e. Oil ring expander
Recommended lubricantEngine oil 
						

							
CRANKSHAFT
5-69
6. Install: Big end bearings
 Connecting rod cap
(onto the connecting rod)
NOTE:
 Align the projections on  the big end bearings 
with the notches in the connecting rods and 
connecting rod caps.
 Make sure that the characters “a” on both the  connecting rod and connecting rod cap are 
aligned.
7. Tighten:  Connecting rod bolts
NOTE:
Install by carrying out the following procedures 
in order to assemble in the most suitable con-
dition.
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a. Replace the connecting rod bolts with new  ones.
b. Clean the connecting rod bolts.
c. After installing the big end bearing, assem- ble the connecting rod and connecting rod 
cap once using a single  unit of the connect-
ing rod.
d. Tighten the connecting rod bolt while  checking that the sections shown “a” and 
“b” are flush with each other by touching 
the surface.
NOTE:
To install the big end bearing, care should be 
taken not to install it at an angle and the posi-
tion should not be out of alignment.
e. Loosen the connecting rod bolt, remove the connecting rod and connecting rod cap and 
install these parts to the crankshaft with the 
big end bearing kept in the current condi-
tion.
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8. Install: Connecting rod assembly
(into the cylinder and onto the crankshaft 
pin)
NOTE:
 While compressing the piston rings with one hand, install the connecting rod assembly 
into the cylinder with the other hand.
 Make sure that the “Y” marks “a” on the con- necting rods face towards the left side of the 
crankshaft.
Connecting rod bolt
24.5 Nm (2.5 m·kg, 17.7 ft·lb)
a. Side machined face
b. Thrusting faces (4 places at front and rear)