Yanmar 3JH4E Service Manual page 129

(3) Measuring the crank pin and journal
Measure the outside diameter, roundness and taper at
each crank pin and journal.
Correct by grinding if unevenly wear, roundness
exceeding the limit or insufficient outside diameter is
found. Replace if the defect is excessive.
Item
Roundness
Taper
To look for the oil clearance of crank pin, measure the
inside diameter of crank pin metal. (Refer to 5.4.2(2). )
Outside dia.
Crank pin
Oil
clearance
Outside dia.
Crank
journal
Oil
clearance
• Dimension R and finishing precision of crankshaft
journal and pin
As for grinding processing of journal and pin, machine
it by using the grinding wheel of the dimension R of
below table.
Surface finishing precision standard on journal and
pin:
Ry=0.8S super polishing
Surface finishing precision standard on the thrust side
of crankshaft arm:
Finishing precision standard of dimension R (mm)
NOTICE:
1) lf the oil clearance is excessive though the thickness of the journal and crankpin metals are normal
or if partial uneven wear is observed, re-grind the crankshaft and use an oversized metals.
2) lf rust or surface roughening exists on the rear side of the metals, coat it with blue or minimum.
Then assemble the crankpin metal to the connecting rod, and tighten the rod bolt to the specified
torque to check the metal for contact. lf the contact surface occupies 75% or more, the metal is
normal. lf the contact surface is insufficient, the metal interference is insufficient. Replace the metal
with a new one.
Limit (Diameter)
0.01
Standard
Ø47.952-
47.962
0.038-
0.074
Ø49.952-
49.962
0.038-
0.068
3.5+0.3/0
5. Inspection and Servicing of Basic Engine Parts
mm
mm
Limit
47.902
0.150
Measuring position of the crank pin
(
and crank journal
49.902
0.150
(Crankshaft R machining)
113
Crankshaft
journal
Crank pin
Super
polishing
Ry=0.8S
Super
Thrust
polishing
face
Ry=0.8S
Crank Pin Crank Journal
)