Engine Service Manual

77
Disassembly/Inspection and Service
32 690 03 Rev. I KohlerEngines.com
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 expander tool. Make
sure identifi cation 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 tool. Make sure
identifi cation mark is up or colored dye stripe (if
contained) is left of end gap.
Remove Crankshaft
Carefully pull crankshaft from crankcase.
Inspection and Service
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. Measure running clearance between
crankshaft journals and their respective bearing bores.
Use an inside micrometer or telescoping gauge to
measure inside diameter of both bearing bores in vertical
and horizontal planes. Use an outside micrometer to
measure outside diameter of crankshaft main bearing
journals. Subtract journal diameters from their respective
bore diameters to get running clearances. Check results
against values in Specifi cations. If running clearances
are within specifi cation, and there is no evidence of
scoring, grooving, etc., no further reconditioning is
necessary. If bearing surfaces are worn or damaged,
crankcase and/or oil pan will need to be replaced.
Inspect crankshaft keyways. If 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 are exceeded, as stated in
Specifi cations, it will be necessary to replace crankshaft.
Remove Flywheel and PTO End Oil Seals
Remove oil seals from crankcase and oil pan.
Crankcase
Inspection and Service
Check all gasket surfaces to make sure they are free of
gasket fragments. Gasket surfaces must also be free of
deep scratches or nicks.
Check cylinder bore for scoring. In severe cases,
unburned fuel can cause scuffi ng and scoring of cylinder
wall. It washes necessary lubricating oils off piston and
cylinder wall. As raw fuel seeps down cylinder wall,
piston rings make metal to metal contact with wall.
Scoring of cylinder wall can also be caused by localized
hot spots resulting from blocked cooling fi ns or from
inadequate or contaminated lubrication.
If cylinder bore is badly scored, excessively worn,
tapered, or out-of-round, resizing is necessary. Use an
inside micrometer to determine amount of wear (refer
to Specifi cations). A 0.25 mm (0.010 in.) oversize piston
is available if resizing is selected. Initially, resize using
a boring bar, then use these following procedures for
honing cylinder.
Honing
Details
A 23°-33° Crosshatch
A
NOTE: Kohler pistons are custom-machined to exacting
tolerances. When over-sizing a cylinder, it
should be machined exactly 0.25 mm (0.010 in.)
over new diameter (refer to Specifi cations).
Oversize Kohler replacement piston will then fi t
correctly.
While most commercially available cylinder hones can
be used with either portable drills or drill presses, use
of a low speed drill press is preferred as it facilitates
more accurate alignment of bore in relation to crankshaft
crossbore. Honing is best accomplished at a drill speed
of about 250 RPM and 60 strokes per minute. After
installing coarse stones in hone, proceed as follows:
1. Lower hone into bore and after centering, adjust so
stones are in contact with cylinder wall. Use of a
commercial cutting-cooling agent is recommended.
2. With lower edge of each stone positioned even with
lowest edge of bore, start drill and honing process.
Move hone up and down while resizing to prevent
formation of cutting ridges. Check size frequently.