Kohler command pro CH940 Service Manual page 65

Piston Style A
1. Cylinder bore must be de-glazed before service ring
sets are used.
2. If cylinder bore does not need re-boring and if old
piston is within wear limits and free of score or scuff
marks, old piston may be reused.
3. Remove old rings and clean up grooves. Never
reuse old rings.
4. Before installing new rings on piston, place top 2
rings, each in turn, in its running area in cylinder
bore and check end gap. Top and middle
compression ring end gap clearance is
0.25/0.56 mm (0.0100/0.0224 in.) for a new bore, or
0.94 mm (0.037 in.) for a used bore.
5. After installing new compression (top and middle)
rings on piston, make sure top compression ring-to-
groove side clearance is 0.025/0.048 mm
(0.0010/0.0019 in.) and middle compression ring-to-
groove side clearance 0.015/0.037 mm
(0.0006/0.0015 in.). If side clearance is greater than
specified, a new piston must be used.
Piston Style B
1. Cylinder bore must be de-glazed before service ring
sets are used.
2. If cylinder bore does not need re-boring and if old
piston is within wear limits and free of score or scuff
marks, old piston may be reused.
3. Remove old rings and clean up grooves. Never
reuse old rings.
4. Before installing new rings on piston, place top 2
rings, each in turn, in its running area in cylinder
bore and check end gap. Top compression ring end
gap clearance is 0.125/0.304 mm (0.0049/0.0120
in.) for a new bore, or 0.515 mm (0.0203 in.) for a
used bore. Middle compression ring end cap is
0.900/1.179 mm (0.0354/0.0464 in.) for a new bore,
or 1.432 mm (0.0564 in.) for a used bore.
5. After installing new compression (top and middle)
rings on piston, make sure top compression ring-to-
groove side clearance and is 0.030/0.070 mm
(0.0010/0.0026 in.) and middle compression ring-to-
groove side clearance 0.030/0.070 mm
(0.0010/0.0026 in.). If side clearance is greater than
specified, a new piston must be used.
62 690 01 Rev. J
Disassembly/Inspection and Service
Install New Piston Rings
Piston Ring Orientation
A
10°
10°
B
Top Oil Ring Rail
A
Intermediate Ring
C
E
Top Ring Gap
NOTE: Rings must be installed correctly. Ring
installation instructions are usually included with
new ring sets. Follow instructions carefully. Use
a piston ring expander to install rings. Install
bottom (oil control) ring first and top
compression ring last.
To install new piston rings, proceed as follows:
1. Oil control ring (bottom groove): Install expander and
then rails. Make sure ends of expander are not
overlapped.
2. Middle compression ring (center groove): Install
center ring using a piston ring installation tool. Make
sure identification mark is up or colored dye stripe
(if contained), is to left of end gap.
3. Top compression ring (top groove): Install top ring
using a piston ring expander. Make sure
identification mark is up or colored dye stripe
(if contained), is to left of end gap.
KohlerEngines.com
E
F
C
Bottom Oil Ring Rail
B
Gap
Oil Ring Expander
D
Gap
F
FLY Stamp
D
Gap
Gap
65