Engine Service Manual

77
Disassembly/Inspection and Service
17 690 01 Rev. J KohlerEngines.com
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. Electric start models can use a smaller starter and
battery more practical for application.
3. 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.
4. Choke control setting is less critical with ACR. In
event of fl ooding, excess fuel is blown out opened
exhaust valve and does not hamper starting.
5. Engines with ACR start much faster in cold weather
than engines without ACR.
6. Engines with ACR can be started with worn or fouled
spark plugs. Engines without ACR are more diffi cult
to start with those same spark plugs.
Inspection and Service
Dimension A
A
CH260/CH270 Cam Lobe
Valve Dimension A Service Limit
INTAKE
27.787 mm
(1.094 in.)
27.533 mm
(1.084 in.)
EXHAUST
27.861 mm
(1.097 in.)
27.607 mm
(1.087 in.)
CH395 Cam Lobe
INTAKE
32.408 mm
(1.276 in.)
32.154 mm
(1.266 in.)
EXHAUST
32.12 mm
(1.265 in.)
31.866 mm
(1.255 in.)
CH440 Cam Lobe
INTAKE
32.286 mm
(1.271 in.)
32.032 mm
(1.261 in.)
EXHAUST
32.506 mm
(1.280 in.)
32.252 mm
(1.270 in.)
Remove Closure Plate
NOTE: Do not pry on gasket surface of crankcase or
closure plate, as this can cause damage and
leakage.
1. Remove screws securing closure plate to crankcase.
2. Remove closure plate, gasket, and dowel pins (if
required) from crankcase.
3. Remove shims from crankshaft and camshaft.
Inspection
Inspect main bearing surface for wear or damage (refer
to Specifi cations). Replace closure plate if required.
Remove Balance Shaft (if equipped)
Remove balance shaft by pulling it straight out of
crankcase.
Remove Camshaft and Valve Tappets
1. Remove camshaft by pulling it straight out of
crankcase.
2. Remove valve tappets by pulling them straight out of
crankcase. Mark their positions.
Automatic Compression Release (ACR)
ACR Operation Details
B
C
E
D
A
A Camshaft B Exhaust Cam Lobe
C
Decompression
Weight
D Return Spring
E Arm
ACR mechanism consists of a spring-loaded arm and
sliding pin mounted to camshaft. When engine is rotating
at low cranking speeds, arm holds pin so it protrudes
above heel of exhaust cam. This holds exhaust valve off
of its seat during fi rst part of compression stroke.
After engine speed increases centrifugal force causes
spring-loaded arm to move outward causing pin to
retract. When in this position pin has no effect on
exhaust valve and engine operates at full compression
and power.