Yamaha MT-09 2021 - Checking the Connecting Rods; Checking the Piston Pin

5-72
CONNECTING RODS AND PISTONS
EAS30749
CHECKING THE PISTON PIN
The following procedure applies to all of the pis-
ton pins.
1. Check:
• Piston pin
Blue discoloration/grooves → Replace the
piston pin and then check the lubrication sys-
tem.
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.
EAS30750
CHECKING THE CONNECTING RODS
1. Measure:
• Crankshaft-pin-to-big-end-bearing clearance
Out of specification → Replace the big end
bearings.
The following procedure applies to all of the con-
necting rods.
NOTICE
ECA13930
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 origi-
nal positions.
a. Clean the big end bearings, crankshaft
pins, and the inside of the connecting rods
halves.
b. Install the big end upper bearing into the
connecting rod and the big end lower bear-
ing into the connecting rod cap with the
connecting rod big end metal installer “1”.
TIP
• From the 3 types, choose the connecting rod
big end metal installer “1” that fits exactly, and
install it to the connecting rod and connecting
rod cap as shown in the illustration.
• Align the projections “a” on the big end bear-
ings with the notches “b” in the connecting rod
and connecting rod cap.
• Push the big end bearing “2” down and install it
to the connecting rod and connecting rod cap.
Piston pin outside diameter limit
16.970 mm (0.6681 in)
Piston pin bore inside diameter
limit
17.043 mm (0.6710 in)
Oil clearance
0.027–0.051 mm (0.0011–0.0020
in)
G089004
b
G089005
Connecting rod big end bearing
installer
90890-04193
Connecting rod big end bearing
installer
YM-04193
1
1