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Crusader
MC-8
MAINTENANCE
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DA rE
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MANUAL
PIP HARK
UP WHEN INSTALLED
ON PISTON
GAP
II
0.005"
- , ~
GRPOVE
Figure 4 - 6: Piston Fits & Tolerances
Used unloader mechanism can be replaced by
unloader kit MCI Part No. 4C- 7-30.
The new unloader pistons should be a loose sliding
fit in the unloader piston bores of the cylinder block.
REPAIRS
DISCHARGE VALVES
&
SEATS: If discharge
valve seats merely show signs of slight wear, they can
be dressed by using a lapping stone, grinding com-
pound and grinding tool. Install new discharge
valves, valve springs, and cap nuts. The discharge
valve travel should be between .030" and .046"
To test for leakage by the discharge valves apply
about I 00 pounds of air pressure through the cylin-
der head discharge port and apply soap suds at the
discharge valves and seats.
If excessive leakage is found, leave the air pressure
applied, and with the use of a fibre or hardwood
dowel and hammer, tap the discharge valves off their
seats several times. This will help the valves to seat
and should reduce any leakage.
With air pressure still applied at the discharge port
of the cylinder head, check .. for leakage at the
discharge valve cap nuts. No leakage is permissible.
INLET VAL YES AND SEA TS: If inlet valve seats
show sign of slight nicks or scratches, they can be
redressed with a fine piece of emery cloth or by lap-
ping with a lapping stone, grinding compound and
grinding tool.
If
the seats are excessively damaged to
the extent that they cannot be reclaimed, they should
be replaced. The dimension from the top of the cylin-
der block to the inlet valve seat should not exceed
0.145" nor be less than 0.101 ".
Slightly worn or scratched inlet valves can be
reclaimed by lapping them on a piece of fine crocus
cloth on a flat surface, but it is suggested that new
inlet valves be installed.
ASSEMBLY
INST ALLING
CYLINDER
BLOCK:
Position
cylinder block gasket and bloc~ on cra!1kcase ac-
cording to markings made pnor to d1sasse'!1bly.
Using cap screws with lockwashers, secure cylinder
block to crankcase.
INST ALLING CRANKSHAFT:
If
the crankshaft
is fitted with oil seal rings, install rings. Position ball
bearings and crankshaft in cr~nkca~~ making sure the
drive end of the crankshaft 1s pos1t10ned as marked
before disassembly.
If
one end of the crankcase is counterbored for
holding a bearing, be sure the crankshaft is installed
· through the correct end of the crankcase.
-
Carefully press crankshaft and bearings into crank-
case using arbor press.
Position a new rear end cover gasket over the rear
end of the crankcase making sure the oil hole in the
gasket lines up with ~he ~ii hole _in t~e crankcase.
Position end cover with
011
seal nng mstalled over
crankcase and end cover gasket. The end cover
should be positioned correctly in relation to the oil
holes in the gasket and crankcase. Secure end covet
to crankcase with cap screws and lockwashers.
If
the opposite end cover requires an oil seal which
was removed on disassembly, a new seal should be
pressed into end cover. Position new end cover
gasket and carefully install end cover over crankshaft
and to crankcase avoiding damage to the seal. Secure
end cover with cap screw and lockwashers.
PISTONS AND CONNECTING RODS:
If
rods are
steel, they can be re-used and serviced as_ follow~.
However it is recommended that the alummum die
cast rods' not be re-used but replaced with new ones
when
re-building compressor.
Do
not ~e-u~e
aluminum die cast connecting rods.
If
new wnst pm
bushings are to be used, they sh_ould b~ pressed i~to
the connecting rods so that the 011 hole m the bus~mg
lines up with the one in the rod. The new bushmgs
should then be reamed or honed to provide between
0.0001" and 0.0006" clearance on the wrist pin.
Position connecting rod in piston and press in wrist
pin so that lockwire hole in th~ pin aligns wi_th that of
the piston. Install new lockw1re t~rough piston _and
wrist pin and lock same by snappmg ~hort end mto
lockwire hole at the bottom of the piston.
Install piston rings in correct locatio~ _with ring
pipmarks up (Figure 4-6). Stagger the pos1t10n of the
ring gaps.
Prelubricate piston, piston rings, ~rist I?in and c~n-
necting rod bearings with clean engme 011 before m-
stalling them in the compressor.
Remove connecting bolts and bearing cap from one
connecting rod. Note: It is important that caps a~d
rods are not intermixed. Turn crankshaft so one of its
connecting rod journals is in ~he downw~rd, c~nter
position. Insert the connectmg rod with piston
through the top of the cylinder. whose journal is
down. Position and attach the beanng cap to the con-
necting rod making sure the bolt_ lockwashers ~re
properly positioned on the cap. Tighten connectmg
rod bolts evenly and bend the two new lockwasher
prongs up against the hex h~ad o~ the bolt. Install the
other connecting rod and piston m the same manner.
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