wall midway between the piston pin
bosses, where the diameter of the piston
is the greatest. Check the fit of the
piston when it is 2 inches down in the
cylinder bore in an inverted position.
The correct piston to cylinder wall
clearance is 0.004 inch.
clearance should be in accordance with
specification shown in the limits and
Inspect the connecting rods for
alignment; straighten or replace all
defective connecting rods.
Inspect piston pin bushings for oil
openings and turning in the connecting
rod. Replace all defective piston pin
bushings. If a new bushing is used, the
piston bushing must be reamed to 0.002
inch clearance of the piston pin, and a
light push with the hand should install
the pin in the bushing at room
Inspect the piston rings for wear, cracks,
breaks, and check the ring end gap
clearance in the cylinder bore. The gap
clearance should be 0.025 inch between
the ring ends with the ring installed in
the cylinder bore. To check the ring
clearance, insert a piston in the cylinder
bore in the inverted position, insert each
piston ring one at a time about 2 inches
down in the cylinder bore, and bring the
bottom edge of the piston up against the
ring to square the ring in the cylinder
bore. Check the ring end gap with a
If the ring end gap
clearance is not as specified, the ring
must be filed or honed to specification,
or the ring must be replaced.
Figure 199. Crane engine piston and connecting
Check the clearance between the
rod assembly, exploded view.
on the crankshaft.
clearance of the connecting rod
small scale of approximately 15 pounds
0.0039 inch maximum. The desired
The correct piston fit is
connecting rod bearing clearance is
obtained when the feeler gauge can be
If the connecting rod
withdrawn from between the piston and
bearing clearance is not specified,
cylinder wall with a pull of 5-10 pounds
replace the connecting rod bearing or
on the scale. The feeler gauge must be
replace the crankshaft.
inserted between the piston and cylinder