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...

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,...

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  →...

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
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”...

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...

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...

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...