Checking The Piston Ring; Checking The Piston Pin - Yamaha YZ85W1 Service Manual

CYLINDER HEAD, CYLINDER AND PISTON
EAS00263

CHECKING THE PISTON RING

1. Measure:
• piston ring side clearance
Out of specification → Replace the piston
and piston ring as a set.
NOTE: NOTE:
Before measuring the piston ring side clear-
ance, eliminate any carbon deposits from the
piston ring grooves and piston ring.
Piston ring side clearance
Piston ring
0.030 ~ 0.065 mm
(0.001 ~ 0.003 in)
<Limit>: 0.1 mm (0.004 in)
2. Install:
• piston ring
(into the cylinder)
NOTE: 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.
Piston ring end gap
Top ring
0.30 ~ 0.45 mm
(0.012 ~ 0.018 in)
<Limit>: 0.80 mm (0.032 in)

CHECKING THE PISTON PIN

1. Check:
• piston pin
Blue discoloration / grooves → Replace the
piston pin and then check the fuel and
engine mixing oil.
2. Measure:
• piston pin outside diameter
Out of specification → Replace the piston
pin.
5-14
ENG