Heavy Duty Balanced Opposed Compressors

FOR MODELS: JG AND JGA SECTION 5 - MAINTENANCE
drive end and auxiliary end straight down into the crankcase, wearing clean
gloves as during removal. Both drive end and auxiliary end journals should
touch the bearing saddles at the same time.
2. When the crankshaft is resting on the bearing saddles, attach the bearing caps
with the capscrews lightly snugged. Then, starting at the thrust end, tighten the
bolts in a crisscross pattern in 25% increments to the recommended torque
value in Table 1-15 on page 1-15. Bearing caps are match-marked to correspond
with the spacer bar and spacer bar bosses on the frame.
3. Be sure the dowels in the bearing caps are aligned with the holes in the crankcase
base. A set screw on top of each dowel prevents it from backing out.
4. Measure each crankshaft journal bearing jack clearance, with a dial indicator
and magnetic stand to Table 1-2 on page 1-8. To measure main bearing clearance,
turn the adjacent crankshaft pin up and mount the indicator stand on the
main bearing cap, with the indicator stem touching the web of the crank adjacent
to the bearing cap. Push down on the crank, set indicator to zero, pry up,
observe and record reading. This is best done before the connecting rods are
installed by pulling a clean lifting strap around the adjacent pin and pulling up on
the crankshaft with a crane or bar on the strap.
5. Reattach the connecting rods (See “Connecting Rod - Installation” on page 5-4),
packing diaphragms, and unloaders/head end heads.
6. Reinstall the chain drive. (See “Chain Drive System” on page 5-12).
7. Replace the spacer bars. Locate the match mark on the spacer bar. Install the
spacer bar so that the match mark is up and next to the spacer bar boss with the
same marking. Tighten bolts to the value in Table 1-15 on page 1-15.
8. Install new end cover gaskets. Examine the top cover gasket. If there is any
doubt that it is not in good usable condition, install a new gasket. Before installing
gaskets, apply an antiseize lubricant to all gaskets or to the metal surfaces
on which they will seat. This will aid in their easy removal at a later date. Trim
the excess from the new end cover gaskets flush to the base with a knife after
end covers have been re-bolted.
9. Reinstall the drive end cover and the top cover. Replace and tighten bolts.
Chain Drive System
Description
The chain drive system is crankshaft-driven at the auxiliary end of the frame. The chain runs
the lube oil pump and force feed lubricator. Chain tightness is controlled by an idler sprocket
attached to the eccentric adjustment cap. The chain dips into the crankcase oil and, as a
result, is constantly lubricated. See Figure 5-7:, for the auxiliary end components and chain
drive system.
Replacement of any parts that can change the position of the drive sprocket on the crankshaft
(i.e. crankshaft, drive sprocket), and/or loss of the as built sprocket position of driven
components, can require repositioning the lube oil pump and force feed lubricator sprockets.
Center crankshaft in end play. With a good straight edge, check to see that sprockets are
aligned within 1/32 inch (1mm). Or measure the distance between the inside face of the aux-
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