10.3
Section 10
Internal Components
10
Clean Cylinder Bore after Honing
Proper cleaning of the cylinder walls following boring
and/or honing is very critical to a successful overhaul.
Machining grit left in the cylinder bore can destroy an
engine in less than one hour of operation after a
rebuild.
The final cleaning operation should always be a
thorough scrubbing with a brush and hot, soapy
water. Use a strong detergent that is capable of
breaking down the machining oil while maintaining a
good level of suds. If the suds break down during
cleaning, discard the dirty water and start again with
more hot water and detergent. Following the
scrubbing, rinse the cylinder with very hot, clear
water, dry it completely, and apply a light coating of
engine oil to prevent rusting.
Measuring Piston-to-Bore Clearance
Before installing the piston into the cylinder bore, it is
necessary that the clearance be accurately checked.
This step is often overlooked, and if the clearances are
not within specifications, engine failure will usually
result.
NOTE:
Do not use a feeler gauge to measure piston-
to-bore clearance - it will yield inaccurate
measurements. Always use a micrometer.
Use the following procedure to accurately measure
the piston-to-bore clearance:
1. With a micrometer, measure the diameter of the
piston perpendicular to the piston pin, and up
from the bottom of the piston skirt as indicated in
Figure 10-2, based on the model involved.
2. Use an inside micrometer, telescoping gauge, or
bore gauge and measure the cylinder bore. Take
the measurement approximately
63.5 mm
(2.5 in.)
below the top of the bore and
perpendicular to the piston pin.
3. Piston-to-bore clearance is the difference between
the bore diameter and the piston diameter (step 2
minus step 1).
Flywheel
Inspection
Inspect the flywheel for cracks, and the flywheel
keyway for damage. Replace flywheel if cracked.
Replace the flywheel, the crankshaft, and the key if
flywheel key is sheared or the keyway damaged.
Inspect the ring gear for cracks or damage. Kohler
does not provide ring gears as a serviceable part.
Replace the flywheel if the ring gear is damaged.
Cylinder Head and Valves
Inspection and Service
Carefully inspect the valve mechanism parts. Inspect
the valve springs and related hardware for excessive
wear or distortion. Check the valves and valve seat
area or inserts for evidence of deep pitting, cracks, or
distortion. Check clearance of the valve stems in
guides. See Figure 10-3 for valve details and
specifications.
Figure 10-2. Measuring Piston Diameter.
6 mm (0.24 in.) on CH11-14 engines
8 mm (0.31 in.) on CH15, 16 engines
Above the Bottom of Piston Skirt
at Right Angels to Piston Pin.
