Heavy Duty Balanced Opposed Compressors

FOR MODELS: JG AND JGA SECTION 5 - MAINTENANCE
TABLE 5-1: CHAIN DEFLECTION LIMITS
COMPRESSOR MODEL
4. Replace the dust plugs in the eccentric adjustment cap to keep dirt out of the
unused holes in the end cover.
Chain and Sprocket Replacement
DEFLECTION LIMITS
FORCE FEED LUBRICATOR TO IDLER, INCHES (mm)
JG/2, JG/4, JGA/2, JGA/4 0.05 to 0.08 (1.3 to 2.0)
JGA/6 0.03 to 0.05 (0.8 to 1.3)
The chain should be replaced if the elongation exceeds 0.084 inches (2.13 mm) over a 10
pitch length. The section of chain to be measured should be stretched tight, in place, in the
compressor and measured with vernier calipers. A reading made outside of the rollers at 10
pitches should be added to a reading between the inside of the same rollers and then be
divided by two. If this calculation exceeds 3.834 inches (97.38 mm) for 3/8 pitch, the chain
should be replaced. Any sprocket showing any undercutting should be replaced.
Eccentric Vernier - Chain Idler Sprocket Replacement
1. A typical chain idler sprocket is shown in Figure 5-8: on Page 5-15.
2. Remove the frame top cover. Remove the dust plugs and the two capscrews
that hold the eccentric adjustment cap to the end cover. Rotate the eccentric cap
to loosen the chain for removal. After dropping the chain off the idler sprocket,
the entire assembly can be removed from the end cover.
3. With a good machinist rule, measure the exact distance from the outer face of
the chain sprocket to the closest face of the eccentric cap. Note the measurement
for the proper positioning of the new sprocket.
4. Remove the locknut, capscrew, sprocket and Stat-O-Seal washer. Discard
these items since they must be replaced with new parts. Remove and discard
the cap O-ring.
5. Reassemble all parts using a new capscrew, Stat-O-Seal washer, sprocket, and
locknut. Compare the sprocket to cap measurement to the measurement previously
taken. If necessary, shim between the cap and the idler spacer to make
the measurements equal. Tighten the idler locknut to the recommended torque
shown in Table 1-15 on page 1-15.
6. Install the assembly on the end cover. Do not install the chain. First check the
alignment to the crankshaft drive sprocket, with crankshaft centered in end play,
using a straight edge.
7. If not in alignment within 1/32 inch (1 mm), shim as necessary, see Figure 5-8:.
8. When the alignment is within 1/32 inch (1 mm), remove the entire assembly
again. Apply oil and install a new O-ring. Install the assembly and adjust the
chain according to the instructions given in “Chain Adjustment” on page 5-13.
PAGE 5 - 14 11/01