Clean Cylinder Bore After Honing; Measuring Piston-To-Bore Clearance; Piston Detail - Kohler Command Pro ECV850 Service Manual

4. After resizing, check bore for roundness, taper, and
size. Use an inside micrometer, telescoping gauge,
or bore gauge to take measurements. These
measurements should be taken at 3 locations in
cylinder – at top, middle, and bottom. There are 2
measurements that should be taken
(perpendicular to each other) at all 3 locations.

Clean Cylinder Bore After Honing

Proper cleaning of cylinder walls following boring and/
or honing is very critical to a successful overhaul.
Machining grit left in cylinder bore can destroy an engine
in less than 1 hour of operation after a rebuild.
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
machining oil while maintaining a good level of suds. If
suds break down during cleaning, discard dirty water and
start again with more hot water and detergent. Following
scrubbing, rinse 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

Piston Detail

A 11 mm (0.4331 in.)
NOTE: Do not use a feeler gauge to measure piston-to-
bore clearance; it will yield inaccurate
measurements. Always use a micrometer.
19 690 01 Rev. --
Disassembly/Inspection and Service
Before installing piston into cylinder bore, it is necessary
that clearance be accurately checked. This step is
often overlooked, and if piston thrust face-to-cylinder
bore running clearance is not within 0.026/0.069 mm
(0.0010/0.0027 in.), engine failure will usually result.
Use following procedure to accurately measure piston-
to-bore clearance:
1. Use a micrometer and measure diameter of piston
11 mm (0.4331 in.) above bottom of piston skirt and
perpendicular to piston pin.
2. Use an inside micrometer, telescoping gauge, or
bore gauge and measure cylinder bore. Take
measurement approximately 63.5 mm (2.5 in.)
below top of bore and perpendicular to piston pin.
3. Piston-to-bore clearance is difference between bore
diameter and piston diameter (step 2 minus step 1).
A
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