Yamaha WR250F 2021 - Installing the Piston and Cylinder

CYLINDER AND PISTON
5-36
3. Measure:
• Piston pin bore inside diameter “b”
Out of specification  Replace the piston.
EAM30100
INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• Top ring “4”
TIP
Be sure to install the piston ring so that the man-
ufacturer’s marks or numbers face up.
2. Install:
• Piston “1”
• Piston pin “2”
• Piston pin clip “3”
TIP
• Apply the engine oil to the piston pin.
• Install the piston with the mark “a” on it pointing
to its exhaust (rear) side.
• Before installing the piston pin clip, cover the
crankcase opening with a cloth to prevent the
clip from falling into the crankcase.
• Make sure that the end of the piston pin clip is
not positioned at the cutout in the piston.
Piston pin outside diameter limit
15.971 mm (0.6288 in)
Piston pin bore inside diameter
limit
16.043 mm (0.6316 in)
b
4
New