SECTION 12
TIRE INFLATION SYSTEM
n. Check fit of wrist pins on pistons and
r. Clearance between the connecting rod
connecting rod bushings. Wrist pin should be
journal and the connecting rod bearing must
light press fit in pistons. If wrist pin is loose
not be less than 0.0003 inch (.00762 mm) or
fit, the pin, piston, or both should be replaced.
more than 0.0021 inch (.0533 mm) after
C h e c k fit of wrist pin in connecting rod
rebuilding.
bushing by rocking the piston. This clearance
should not exceed 0.0015 inch (.0381 mm).
s. Check for wear or flat spots; If found,
R e p l a c e wrist pin bushings if excessive
bearings should be replaced. If type with
clearance is found. Wrist pin bushings should
sleeve bearing, this bearing should be checked
be reamed after being pressed into connecting
for scores and wear and replaced if necessary.
rods. Replace used wrist pin lock wires.
t. Used unloader mechanism should be
o. Check fit of piston rings in piston ring
replaced by Repair Kit (refer to parts manual).
grooves. Check ring gap with rings installed in
The new unloader pistons should be a loose
cylinder bores. Refer to figure 12-10 for correct
sliding fit in the unloader piston bores of the
gap and groove clearance.
cylinder block.
12-31.
REPAIR.
a. If discharge valves show slight wear,
dress them by using a lapping stone, grinding
compound and grinding tool. If discharge valve
seats merely show signs of slight wear, they
can be dressed by using a lapping stone,
grinding compound and grinding tool. install
new discharge valves, valve springs and cap
nuts. The discharge valve travel should be
between .036 -.058 inch (.914 - 1.473 mm).
b. To test for leakage by the discharge
valves, apply about 100 PSI (7.0 kg/cm2 ) of air
pressure through the cylinder head discharge
port and apply soap suds at the discharge
valves and seats. Leakage forming soap
bubbles is permissible.
FIGURE 12-9.
c. If excessive leakage is found, leave the air
p. Check crankshaft screw threads, keyways,
pressure applied and, with the use of a fibre or
tapered ends and all machined and ground
h a r d w o o d dowel and hammer, tap the
surfaces for wear, scores or damage. Crank-
discharge valves off their seats several times.
shaft journals which are out of round more
This will help the valves to seat and should
than 0.001 inch (.0254 mm) must be reground.
reduce any leakage.
Bearing inserts are available in 0.010, 0.020,
and 0.030 Inch (.254, 508, and .762 mm)
d. With the air pressure still applied at the
undersizes for reground crankshafts. Main
discharge port of the cylinder head, check for
bearing journals m u s t be maintained so
leakage at the discharge valve cap nuts. No
bearings are snug fit. The oil seal ring groove
leakage is permissible.
or grooves in crankshafts fitted with oilseal
rings must not be worn. The ring groove walls
e. If inlet valve seats show slight nicks or
must have a good finish and they must be
scratches, they can be redressed with a fine
square. Make sure the oil passages are open
piece of emery cloth or by lapping with a
and clean through the crankshaft.
lapping stone, grinding compound and grinding
tools. If the seats are excessively damaged to
q. Check connecting rod bearings on crank-
the extent that they cannot be reclaimed, they
shaft journals for proper fit. Used bearing
should be replaced. The dimension from the
Inserts should be replaced. Connecting rod
top of the cylinder block to the inlet valve seat
caps are not interchangeable. The locking slots
should not exceed 0.145 inch (3.663 mm) nor
of the connecting rod and cap should be
be less than 0.101 inch (2.565 mm).
positioned adjacent to each other.
12-7.
