instructions (Figure 134). T h e standard
crankshaft main bearing clearance is 0.0009 in.
(0.022 mm). The maximum (service limit) is
0.004 in. (0.10 mm).
13. Compare both ends of the Plastigage strip.
A difference of 0.001 in. (0.025 mm) or more
indicates a tapered journal which should be
reground. C o n f i r m w i t h m i c r o m e t e r
measurement of the journal OD.
14. If the clearance is larger than the service
limit, measure the O D of the crankshaft main
journal with a micrometer. The minimum
main journal OD (service limit) is given in
a. Ifthe OD is smaller than the service limit,
the crankshaft should be replaced.
b. If the OD is larger than the service limit,
install new bearing inserts. Always
replace all 10 inserts at the same time.
Several different insert thicknesses are
available and they are color-coded for
size. Refer t o T a b l e 1 for insert
c. Recheck the clearance with the new
inserts. The clearance should be less than
the service limit and as close to standard
You can install the thinnest new inserts,
recheck clearance and install thicker
inserts ifthe clearance wasn't correct, or
you can calculate the required insert
Assemble t h e crankcase halves
without the inserts or crankshaft and
measure the crankcase ID.
2. Subtract the crankshaft main journal
ODfrom the crankcase ID, then subtract
the standard clearance-0.0009 in.
(0.022 mm). The number you get will be
twice the thickness of the required
3. Divide by 2 for the appropriate insert
15. Clean and oil the main bearing journals
and insert faces.
16. Install the bearing inserts in the crankcase
halves. Make sure their locking tabs are seated
in the notches.
If the old inserts are reused, be sure they
are installed in their original positions
for minimum wear.
Connecting Rod Big-end
Make a note of the bearing size (if any)
stamped on the back of the insert. If the insert
is color-coded with paint on the edge, note the
2. Check the inside and outside surfaces ofthe
bearing inserts for wear, a bluish tint (burned),
flaking, abrasion and scoring. If the inserts are
good, they may be reused if clearance is
satisfactory. If any insert is questionable,
replace the entire set.
3. Wipe oil from the crankpin journals and the
Install the inserts in the connecting rod and
cap. Make sure their locking tabs are seated in
the notches (Figure 132).
5. Place a piece of Plastigage on one crankpin
parallel to the crankshaft.
6. Install the rod cap and torque the nuts as
specified in Table 2.
Do not place the Plastigage over the oil
holes. Do not rotate the connecting rod
while Plastigage is in place.
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