Kohler Command Pro CV173 Service Manual page 48

Disassembly/Inspection and Service
Crankcase Components
M
L
A Crankcase Oil Seal
C Piston Pin Retainer
E Piston
G Crankcase Bearing
Connecting Rod End
I
Cap
K Camshaft
M Camshaft Washer
Remove Camshaft
Remove camshaft with wave spring and camshaft
washer from crankcase.
Inspection and Service
Inspect gear teeth of camshaft. If teeth are badly worn
or chipped, or if some are missing, replacement of
camshaft will be necessary. If unusual wear or damage
is evident on either camshaft lobes or mating valve lifters
camshaft and both valve lifters must be replaced. Check
condition and operation of Automatic Compression
Release (ACR) mechanism.
48
A
B
C
D
F
G
E
C
H
I
J
K
B Crankcase
D Piston Pin
F Crankshaft
H Connecting Rod
J Valve Lifters
L Wave Spring
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ACR
These engines are equipped with an ACR mechanism.
ACR lowers compression at cranking speeds to make
starting easier.
ACR mechanism consists of a decompression weight
and arm mounted to camshaft, and activated by a return
spring. When engine is rotating at low cranking speeds
(1000 RPM or less), decompression weight holds arm
so it protrudes above heel of exhaust lobe. This holds
exhaust valve off its seat during fi rst part of compression
stroke.
After engine speed increases above approximately 1000
RPM, centrifugal force causes decompression weight
to move outward, causing arm to retract. When in this
position, arm has no eff ect on exhaust valve and engine
operates at FULL compression and power.
Benefi ts
As a result of reduced compression at cranking speeds,
several important benefi ts are obtained:
1. Manual (retractable) starting is much easier. Without
ACR, manual starting would be virtually impossible.
2. ACR eliminates need for a spark retard/advance
mechanism. A spark retard/advance mechanism
would be required on engines without ACR to
prevent kickback which would occur during starting.
ACR eliminates this kickback, making manual
starting safer.
3. Choke control setting is less critical with ACR. If
fl ooding occurs, excess fuel is blown out opened
exhaust valve and does not hamper starting.
4. Engines with ACR start much faster in cold weather
than engines without ACR.
5. Engines with ACR can be started with spark plugs
which are worn or fouled. Engines without ACR are
more diffi cult to start with those same spark plugs.
Remove Valve Lifters
Remove valve lifters. Mark them INTAKE and EXHAUST
for reinstallation.
Remove Connecting Rod Cap
Rotate crankshaft to allow access to 2 screws on
connecting rod cap. Remove screws and cap. Note
position of match marks (to oil pan side).
Remove Piston and Connecting Rod
Carefully guide piston and attached connecting rod out
of cylinder bore.
Connecting Rod Inspection and Service
Check bearing area (big end) for excessive wear, score
marks, running and side clearances. Replace connecting
rod and end cap if scored or excessively worn.
Service replacement connecting rods are available in
STD size.
Piston and Rings Inspection
Scuffi ng and scoring of pistons and cylinder walls occurs
when internal engine temperatures approach welding
point of piston. Temperatures high enough to do this are
created by friction, which is usually attributed to improper
lubrication and/or overheating of engine.
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