Kohler CH18-CH26 Service Manual page 200

Section 10
Inspection and Reconditioning
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. Use a micrometer and measure the diameter of
the piston 6 mm (0.24 in.) above the bottom of the
piston skirt and perpendicular to the piston pin.
See Figure 10-4.
Measure 6 mm above the
Bottom of Piston Skirt at
Right Angles to Piston Pin
Figure 10-4. Measuring Piston Diameter.
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.
10.4
Flywheel
Inspection
Inspect the flywheel for cracks and the flywheel
keyway for damage. Replace the flywheel if it is
cracked. Replace the flywheel, the crankshaft, and the
key if flywheel key is sheared or the keyway is
damaged.
Inspect the ring gear for cracks or damage. Kohler
does not provide the ring gear as a serviceable part.
Replace the flywheel if the ring gear is damaged.
Cylinder Head and Valves
Inspection and Service
After cleaning, check the flatness of the cylinder head
and the corresponding top surface of the crankcase,
using a surface plate or piece of glass and feeler gauge
as shown in Figure 10-5. The maximum allowable out
of flatness is 0.076 mm (0.003 in.).
6 mm (0.24 in.)
Figure 10-5. Checking Cylinder Head Flatness.
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 the
guides. See Figure 10-6 for valve details and
specifications.
3. Piston-to-bore clearance is the difference
between the bore diameter and the piston
diameter (step 2 minus step 1).