Yamaha YZF-R25 Service Manual page 255

TIP
• Install the oil ring expander as shown in the il-
lustration.
• Be sure to install the piston rings so that the
manufacturer marks "a" face up.
a
2. Install:
• Piston "1"
• Piston pin "2"
• Piston pin clips "3"
TIP
• Apply engine oil onto the piston pin.
• Make sure the punch mark "a" on the piston
points towards the exhaust side of the engine.
• Before installing the piston pin clips, cover the
crankcase opening with a clean rag to prevent
the piston pin clips from falling into the crank-
case.
• When installing a piston pin clip, make sure
that the clip ends "b" are pistoned away from
the cutout "c" in the piston as shown in the illus-
tration.
• Reinstall each piston into its original cylinder
(numbering order starting from the left: #1 to
#2).
a
a
5
4
3
1
2
New
1 2 3 New
CYLINDER AND PISTONS
1
2
3. Lubricate:
• Piston
• Piston rings
• Cylinder
(with the recommended lubricant)
Recommended lubricant
Engine oil
4. Offset:
• Piston ring end gaps
b
135˚
45˚
a
45˚
e
a. Top ring
b. Oil ring expander
c. Lower oil ring rail
d. 2nd ring
e. Upper oil ring rail
A. Exhaust side
5. Install:
• Dowel pins
New
• O-ring
• Cylinder gasket
6. Install:
• Cylinder "1"
TIP
• While compressing the piston rings, install the
cylinder.
• Pass the timing chain and timing chain guide
(intake side) through the timing chain cavity.
5-38
c
3 New
A
c
45˚ 45˚
45˚
d
New
b