Yanmar 3JH4E, Service Manual

Page: 226 / 350

5. Inspection and servicing of basic engine parts
206
(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.
To look for the oil clearance of crank pin, measure
the inside diameter of crank pin metal. (Refer to
5.4.2(2).)
• 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:
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.
mm
Item Limit (Diameter)
Roundness taper 0.01
mm
Standard Limit
Crank
pin
Outside dia. 47.952-47.962 47.902
Oil clearance 0.038-0.083 0.150
Crank
journal
Outside dia. 49.952-49.962 49.902
Oil clearance 0.038-0.068 0.150
Finishing precision standard of dimension R (mm)
3.5
+0.3
0
008298-00X
007528-00X
Super
polishing
Super
polishing
Thrust
face
Crank pin Crank Journal
Ry=0.8S
Ry=0.8S
R
R
R
R
R
010641-00E
1.6