Kohler Aegis LH775 Service Manual page 72

Disassembly/Inspection and Service
Install New Piston Rings
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 fi rst 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 identifi cation mark is up or dye colored stripe (if
contained) is to left of end gap.
3. Top compression ring (top groove): Install top ring
using a piston ring expender. Make sure
identifi cation mark is up or dye colored stripe (if
contained), left of end gap.
Connecting Rods
Offset, stepped-cap connecting rods are used in all
these engines.
Inspection and Service
Check bearing area (big end) for excessive wear, score
marks, running and side clearances. Replace rod and
cap if scored or excessively worn.
Service replacement connecting rods are available in
STD crankpin size and 0.25 mm (0.010 in.) undersize.
An 0.25 mm (0.010 in.) undersized rod can be identifi ed
by a drilled hole located in lower end of rod shank.
Always refer to appropriate parts information to ensure
correct replacements are used.
Remove Crankshaft
1. Carefully pull crankshaft from crankcase. Note thrust
washer and shims if used.
Inspection and Service
Crankshaft Components and Details
A Self-Tapping Screw
C Plug
72
A
B
C
D
B Flat Washer
D Crankshaft
KohlerEngines.com
G
E
Fillet Must Blend Smoothly with Bearing Journal
E
F High Point from Fillet Intersections
G
H This Fillet Area Must Be Completely Smooth
Inspect gear teeth of crankshaft. If teeth are badly worn,
chipped, or some are missing, replacement of crankshaft
will be necessary.
Inspect crankshaft bearing surfaces for scoring,
grooving, etc. Replaceable bearing is used in crankshaft
bore of closure plate and/or crankcase. Do not replace
bearing unless they show signs of damage or are out of
running clearance 0.039/0.074 mm (0.0015/0.0029 in.).
If crankshaft turns easily, without noise, and there is no
evidence of scoring, grooving, etc., on races or bearing
surfaces, bearing can be reused.
Inspect crankshaft keyways. If they are worn or chipped,
replacement of crankshaft will be necessary. Inspect
crankpin for score marks or metallic pickup. Slight score
marks can be cleaned with crocus cloth soaked in oil. If
wear limits, as stated in Clearance Specifi cations, are
exceeded, it will be necessary to replace crankshaft or
regrind crankpin to 0.25 mm (0.010 in.) undersize. If
reground, a 0.25 mm (0.010 in.) undersize connecting
rod (big end) must then be used to achieve proper
running clearance. Measure crankpin for size, taper, and
out-of-round.
Connecting rod journal can be ground 1 size under.
When grinding a crankshaft, grinding stone deposits
can get caught in oil passages, which could cause
severe engine damage. Removing crankpin plug when
crankshaft is ground provides easy access for removing
any grinding deposits that may collect in oil passages.
Use following procedure to remove and replace plug.
Remove Crankshaft Plug
1. Drill a 3/16 in. hole through plug in crankshaft.
2. Thread a 3/4 in. or 1 in. long self-tapping screw with
a fl at washer into drilled hole. Flat washer must be
large enough to seat against shoulder of plug bore.
3. Tighten self-tapping screw until it draws plug out of
crankshaft.
Install New Crankshaft Plug
Use 1 single cylinder camshaft pin, as a driver and tap
plug into plug bore until it seats at bottom of bore. Make
sure plug is tapped in evenly to prevent leakage.
F
H
Surface
45° Minimum
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