TOHATSU BFT 250A, Service Manual

Page: 448 / 639

15-34
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CYLINDER BLOCK
CRANKSHAFT MAIN BEARING OIL
CLEARANCE
To check main bearing-to-journal oil clearance, remove
the bearing caps, crankshaft, and main bearings (page
15-7).
Clean each main journal and main bearings with a
clean shop towel.
Check each main journal, thrust washer contact
surface, main bearing for scoring, scratches or damage.
Install the main bearings, crankshaft, and bearing caps,
and tighten the cap bolts to the specified torque (page
15-17).
Remove the bearing caps and place one strip of
plastigauge [1] across each main journal.
• Set the plastigauge in the axial direction.
• Avoid the oil passage in the bearing journal to set
the plastigauge.
Reinstall the bearings and caps.
Tighten the bolts to the specified torque (page 15-17).
• Do not turn the crankshaft during this check.
Remove the bearing caps and measure the pressured
width of the plastigauge using the scale [2] printed on
the plastigauge’s bag.
• Take the widest width on the plastigauge.
If the measurement exceeds the service limit, replace
the bearings by referring to crankshaft main bearing
selection table (page 15-36) and measure the oil
clearance again.
If the measurement still exceeds the service limit,
replace the crankshaft with a new one and recheck.
STANDARD:
0.020 – 0.046 mm (0.0008 – 0.0018 in)
SERVICE LIMIT:
0.05 mm (0.002 in)
[2]
[1]